Extraordinary sex ratios: cultural effects on ecological consequences.

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Ferenc Molnár

Full Text Available We model sex-structured population dynamics to analyze pairwise competition between groups differing both genetically and culturally. A sex-ratio allele is expressed in the heterogametic sex only, so that assumptions of Fisher's analysis do not apply. Sex-ratio evolution drives cultural evolution of a group-associated trait governing mortality in the homogametic sex. The two-sex dynamics under resource limitation induces a strong Allee effect that depends on both sex ratio and cultural trait values. We describe the resulting threshold, separating extinction from positive growth, as a function of female and male densities. When initial conditions avoid extinction due to the Allee effect, different sex ratios cannot coexist; in our model, greater female allocation always invades and excludes a lesser allocation. But the culturally transmitted trait interacts with the sex ratio to determine the ecological consequences of successful invasion. The invading female allocation may permit population persistence at self-regulated equilibrium. For this case, the resident culture may be excluded, or may coexist with the invader culture. That is, a single sex-ratio allele in females and a cultural dimorphism in male mortality can persist; a low-mortality resident trait is maintained by father-to-son cultural transmission. Otherwise, the successfully invading female allocation excludes the resident allele and culture and then drives the population to extinction via a shortage of males. Finally, we show that the results obtained under homogeneous mixing hold, with caveats, in a spatially explicit model with local mating and diffusive dispersal in both sexes.

Adult sex ratio variation: implications for breeding system evolution.

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Székely, T; Weissing, F J; Komdeur, J

2014-08-01

Adult sex ratio (ASR) exhibits immense variation in nature, although neither the causes nor the implications of this variation are fully understood. According to theory, the ASR is expected to influence sex roles and breeding systems, as the rarer sex in the population has more potential partners to mate with than the more common sex. Changes in mate choice, mating systems and parental care suggest that the ASR does influence breeding behaviour, although there is a need for more tests, especially experimental ones. In the context of breeding system evolution, the focus is currently on operational sex ratios (OSRs). We argue that the ASR plays a role of similar importance and urge researchers to study the ASR and the OSR side by side. Finally, we plead for a dynamic view of breeding system evolution with feedbacks between mating, parenting, OSR and ASR on both ecological and evolutionary time scales. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Sex ratios in the two Germanies: a test of the economic stress hypothesis.

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Catalano, Ralph A

2003-09-01

Literature describing temporal variation in the secondary sex ratio among humans reports an association between population stressors and declines in the odds of male birth. Explanations of this phenomenon draw on reports that stressed females spontaneously abort male more than female fetuses, and that stressed males exhibit reduced sperm motility. This work has led to the argument that population stress induced by a declining economy reduces the human sex ratio. No direct test of this hypothesis appears in the literature. Here, a test is offered based on a comparison of the sex ratio in East and West Germany for the years 1946 to 1999. The theory suggests that the East German sex ratio should be lower in 1991, when East Germany's economy collapsed, than expected from its own history and from the sex ratio in West Germany. The hypothesis is tested using time-series modelling methods. The data support the hypothesis. The sex ratio in East Germany was at its lowest in 1991. This first direct test supports the hypothesis that economic decline reduces the human sex ratio.

Skewed sex ratios in India: "physician, heal thyself".

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Patel, Archana B; Badhoniya, Neetu; Mamtani, Manju; Kulkarni, Hemant

2013-06-01

Sex selection, a gender discrimination of the worst kind, is highly prevalent across all strata of Indian society. Physicians have a crucial role in this practice and implementation of the Indian Government's Pre-Natal Diagnostic Techniques Act in 1996 to prevent the misuse of ultrasound techniques for the purpose of prenatal sex determination. Little is known about family preferences, let alone preferences among families of physicians. We investigated the sex ratios in 946 nuclear families with 1,624 children, for which either one or both parents were physicians. The overall child sex ratio was more skewed than the national average of 914. The conditional sex ratios decreased with increasing number of previous female births, and a previous birth of a daughter in the family was associated with a 38 % reduced likelihood of a subsequent female birth. The heavily skewed sex ratios in the families of physicians are indicative of a deeply rooted social malady that could pose a critical challenge in correcting the sex ratios in India.

Using Approximate Bayesian Computation to infer sex ratios from acoustic data.

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Lehnen, Lisa; Schorcht, Wigbert; Karst, Inken; Biedermann, Martin; Kerth, Gerald; Puechmaille, Sebastien J

2018-01-01

Population sex ratios are of high ecological relevance, but are challenging to determine in species lacking conspicuous external cues indicating their sex. Acoustic sexing is an option if vocalizations differ between sexes, but is precluded by overlapping distributions of the values of male and female vocalizations in many species. A method allowing the inference of sex ratios despite such an overlap will therefore greatly increase the information extractable from acoustic data. To meet this demand, we developed a novel approach using Approximate Bayesian Computation (ABC) to infer the sex ratio of populations from acoustic data. Additionally, parameters characterizing the male and female distribution of acoustic values (mean and standard deviation) are inferred. This information is then used to probabilistically assign a sex to a single acoustic signal. We furthermore develop a simpler means of sex ratio estimation based on the exclusion of calls from the overlap zone. Applying our methods to simulated data demonstrates that sex ratio and acoustic parameter characteristics of males and females are reliably inferred by the ABC approach. Applying both the ABC and the exclusion method to empirical datasets (echolocation calls recorded in colonies of lesser horseshoe bats, Rhinolophus hipposideros) provides similar sex ratios as molecular sexing. Our methods aim to facilitate evidence-based conservation, and to benefit scientists investigating ecological or conservation questions related to sex- or group specific behaviour across a wide range of organisms emitting acoustic signals. The developed methodology is non-invasive, low-cost and time-efficient, thus allowing the study of many sites and individuals. We provide an R-script for the easy application of the method and discuss potential future extensions and fields of applications. The script can be easily adapted to account for numerous biological systems by adjusting the type and number of groups to be

Invited review: sex ratio and rheumatic disease.

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Lockshin, M D

2001-11-01

Human illnesses affect men and women differently. In some cases (diseases of sex organs, diseases resulting from X or Y chromosome mutations), reasons for sex discrepancy are obvious, but in other cases no reason is apparent. Explanations for sex discrepancy of illness occur at different biological levels: molecular (e.g., imprinting, X-inactivation), cellular (sex-specific receptor activity), organ (endocrine influences), whole organism (size, age), and environmental-behavioral, including intrauterine influences. Autoimmunity represents a prototypical class of illness that has high female-to-male (F/M) ratios. Although the F/M ratios in autoimmune diseases are usually attributed to the influence of estrogenic hormones, evidence demonstrates that the attributed ratios are imprecise and that definitions and classifications of autoimmune diseases vary, rendering at least part of the counting imprecise. In addition, many studies on sex discrepancy of human disease fail to distinguish between disease incidence and disease severity. In April 2001, the Institute of Medicine of the National Academy of Sciences published Exploring the Biological Contributions to Human Health: Does Sex Matter? (Wizemann T and Pardue M-L, editors). This minireview summarizes the section of that report that concerns autoimmune and infectious disease. Some thyroid, rheumatic, and hepatic autoimmune diseases have high F/M ratios, whereas others have low. Those that have high ratios occur primarily in young adulthood. Gonadal hormones, if they play a role, likely do so through a threshold or permissive mechanism. Examples of sex differences that could be caused by environmental exposure, X inactivation, imprinting, X or Y chromosome genetic modulators, and intrauterine influences are presented as alternate, theoretical, and largely unexplored explanations for sex differences of incidence. The epidemiology of autoimmune diseases (young, female) suggests that an explanation for sex discrepancy of

Do Workplace Sex Ratios Affect Partnership Formation and Dissolution?

DEFF Research Database (Denmark)

Svarer, Michael

In this paper, I analyse the association between workplace sex ratios and partnership formation and dissolution. I find that the risk of dissolution increases with the fraction of coworkers of the opposite sex at both the female and male workplace. On the other hand, workplace sex ratios are not ......In this paper, I analyse the association between workplace sex ratios and partnership formation and dissolution. I find that the risk of dissolution increases with the fraction of coworkers of the opposite sex at both the female and male workplace. On the other hand, workplace sex ratios...

Sex ratios of Mountain Plovers from egg production to fledging

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Margaret M. Riordan

2015-12-01

Full Text Available Skewed sex ratios can have negative implications for population growth if they do not match a species' life history. A skewed tertiary sex ratio has been detected in a population of Mountain Plover (Charadrius montanus, a grassland shorebird experiencing population declines. To study the cause of the observed male skew, we examined three early life stages between egg and fledgling in eastern Colorado from 2010 to 2012. This allows us to distinguish between egg production and chick survival as an explanation for the observed skew. We examined the primary sex ratio in eggs produced and the secondary sex ratio in hatched chicks to see if the sex ratio bias occurs before hatching. We also determined the sex ratio at fledging to reveal sex-specific mortality of nestlings. The primary sex ratio was 1.01 (± 0.01 males per female. The secondary sex ratio consisted of 1.10 (± 0.02 males per female. The probability of a chick surviving to fledging differed between males (0.55 ± 0.13 and females (0.47 ± 0.15, but the precision of these survival estimates was low. Sex ratios in early life stages of the Mountain Plover do not explain the skewed sex ratio observed in adults in this breeding population.

Density-dependent sex ratio and sex-specific preference for host traits in parasitic bat flies.

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Szentiványi, Tamara; Vincze, Orsolya; Estók, Péter

2017-08-29

Deviation of sex ratios from unity in wild animal populations has recently been demonstrated to be far more prevalent than previously thought. Ectoparasites are prominent examples of this bias, given that their sex ratios vary from strongly female- to strongly male-biased both among hosts and at the metapopulation level. To date our knowledge is very limited on how and why these biased sex ratios develop. It was suggested that sex ratio and sex-specific aggregation of ectoparasites might be shaped by the ecology, behaviour and physiology of both hosts and their parasites. Here we investigate a highly specialised, hematophagous bat fly species with strong potential to move between hosts, arguably limited inbreeding effects, off-host developmental stages and extended parental care. We collected a total of 796 Nycteribia kolenatii bat flies from 147 individual bats using fumigation and subsequently determined their sex. We report a balanced sex ratio at the metapopulation level and a highly variable sex ratio among infrapopulations ranging from 100% male to 100% female. We show that infrapopulation sex ratio is not random and is highly correlated with infrapopulation size. Sex ratio is highly male biased in small and highly female biased in large infrapopulations. We show that this pattern is most probably the result of sex-specific preference in bat flies for host traits, most likely combined with a higher mobility of males. We demonstrate that female bat flies exert a strong preference for high host body condition and female hosts, while the distribution of males is more even. Our results suggest that locally biased sex ratios can develop due to sex-specific habitat preference of parasites. Moreover, it is apparent that the sex of both hosts and parasites need to be accounted for when a better understanding of host-parasite systems is targeted.

The evolution of sex roles in birds is related to adult sex ratio.

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Liker, András; Freckleton, Robert P; Székely, Tamás

2013-01-01

Sex-role reversal represents a formidable challenge for evolutionary biologists, since it is not clear which ecological, life-history or social factors facilitated conventional sex roles (female care and male-male competition for mates) to be reversed (male care and female-female competition). Classic theories suggested ecological or life-history predictors of role reversal, but most studies failed to support these hypotheses. Recent theory however predicts that sex-role reversal should be driven by male-biased adult sex ratio (ASR). Here we test this prediction for the first time using phylogenetic comparative analyses. Consistent with theory, both mating system and parental care are strongly related to ASR in shorebirds: conventional sex roles are exhibited by species with female-biased ASR, whereas sex-role reversal is associated with male-biased ASR. These results suggest that social environment has a strong influence on breeding systems and therefore revealing the causes of ASR variation in wild populations is essential for understanding sex role evolution.

Curious Sex Ratios and Cytoplasmic Genes

Indian Academy of Sciences (India)

instances of curious sex ratios exemplify an important principle: the fitness ..... markable transition - the whole means of sex determination has changed. No longer ... to the cytoplasmic symbiont is self-evident; the symbionts simply increase the.

Genetic architecture of sex determination in fish: Applications to sex ratio control in aquaculture

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Paulino eMartínez

2014-09-01

Full Text Available Controlling the sex ratio is essential in finfish farming. A balanced sex ratio is usually good for broodstock management, since it enables to develop appropriate breeding schemes. However, in some species the production of monosex populations is desirable because the existence of sexual dimorphism, primarily in growth or first time of sexual maturation, but also in color or shape, can render one sex more valuable. The knowledge of the genetic architecture of sex determination (SD is convenient for controlling sex ratio and for the implementation of breeding programs. Unlike mammals and birds, which show highly conserved master genes that control a conserved genetic network responsible for gonad differentiation (GD, a huge diversity of SD mechanisms has been reported in fish. Despite theory predictions, more than one gene is in many cases involved in fish SD and genetic differences have been observed in the GD network. Environmental factors also play a relevant role and epigenetic mechanisms are becoming increasingly recognized for the establishment and maintenance of the GD pathways. Although major genetic factors are frequently involved in fish SD, these observations strongly suggest that SD in this group resembles a complex trait. Accordingly, the application of quantitative genetics combined with genomic tools is desirable to address its study and in fact, when applied, it has frequently demonstrated a multigene trait interacting with environmental factors in model and cultured fish species. This scenario has notable implications for aquaculture and, depending upon the species, from chromosome manipulation or environmental control techniques up to classical selection or marker assisted selection programs, are being applied. In this review, we selected four relevant species or fish groups to illustrate this diversity and hence the technologies that can be used by the industry for the control of sex ratio: turbot and European sea bass, two

Skewed sex ratios and criminal victimization in India.

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South, Scott J; Trent, Katherine; Bose, Sunita

2014-06-01

Although substantial research has explored the causes of India's excessively masculine population sex ratio, few studies have examined the consequences of this surplus of males. We merge individual-level data from the 2004-2005 India Human Development Survey with data from the 2001 India population census to examine the association between the district-level male-to-female sex ratio at ages 15 to 39 and self-reports of victimization by theft, breaking and entering, and assault. Multilevel logistic regression analyses reveal positive and statistically significant albeit substantively modest effects of the district-level sex ratio on all three victimization risks. We also find that higher male-to-female sex ratios are associated with the perception that young unmarried women in the local community are frequently harassed. Household-level indicators of family structure, socioeconomic status, and caste, as well as areal indicators of women's empowerment and collective efficacy, also emerge as significant predictors of self-reported criminal victimization and the perceived harassment of young women. The implications of these findings for India's growing sex ratio imbalance are discussed.

Skewed Sex Ratios and Criminal Victimization in India

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South, Scott J.; Trent, Katherine; Bose, Sunita

2014-01-01

Although substantial research has explored the causes of India’s excessively masculine population sex ratio, few studies have examined the consequences of this surplus of males. We merge individual-level data from the 2004–2005 India Human Development Survey with data from the 2001 India population census to examine the association between the district-level male-to-female sex ratio at ages 15 to 39 and self-reports of victimization by theft, breaking and entering, and assault. Multilevel logistic regression analyses reveal positive and statistically significant albeit substantively modest effects of the district-level sex ratio on all three victimization risks. We also find that higher male-to-female sex ratios are associated with the perception that young unmarried women in the local community are frequently harassed. Household-level indicators of family structure, socioeconomic status, and caste, as well as areal indicators of women’s empowerment and collective efficacy, also emerge as significant predictors of self-reported criminal victimization and the perceived harassment of young women. The implications of these findings for India’s growing sex ratio imbalance are discussed. PMID:24682921

Inter-Annual Variability of Fledgling Sex Ratio in King Penguins.

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Célia Bordier

Full Text Available As the number of breeding pairs depends on the adult sex ratio in a monogamous species with biparental care, investigating sex-ratio variability in natural populations is essential to understand population dynamics. Using 10 years of data (2000-2009 in a seasonally monogamous seabird, the king penguin (Aptenodytes patagonicus, we investigated the annual sex ratio at fledging, and the potential environmental causes for its variation. Over more than 4000 birds, the annual sex ratio at fledging was highly variable (ranging from 44.4% to 58.3% of males, and on average slightly biased towards males (51.6%. Yearly variation in sex-ratio bias was neither related to density within the colony, nor to global or local oceanographic conditions known to affect both the productivity and accessibility of penguin foraging areas. However, rising sea surface temperature coincided with an increase in fledging sex-ratio variability. Fledging sex ratio was also correlated with difference in body condition between male and female fledglings. When more males were produced in a given year, their body condition was higher (and reciprocally, suggesting that parents might adopt a sex-biased allocation strategy depending on yearly environmental conditions and/or that the effect of environmental parameters on chick condition and survival may be sex-dependent. The initial bias in sex ratio observed at the juvenile stage tended to return to 1∶1 equilibrium upon first breeding attempts, as would be expected from Fisher's classic theory of offspring sex-ratio variation.

Inter-Annual Variability of Fledgling Sex Ratio in King Penguins.

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Bordier, Célia; Saraux, Claire; Viblanc, Vincent A; Gachot-Neveu, Hélène; Beaugey, Magali; Le Maho, Yvon; Le Bohec, Céline

2014-01-01

As the number of breeding pairs depends on the adult sex ratio in a monogamous species with biparental care, investigating sex-ratio variability in natural populations is essential to understand population dynamics. Using 10 years of data (2000-2009) in a seasonally monogamous seabird, the king penguin (Aptenodytes patagonicus), we investigated the annual sex ratio at fledging, and the potential environmental causes for its variation. Over more than 4000 birds, the annual sex ratio at fledging was highly variable (ranging from 44.4% to 58.3% of males), and on average slightly biased towards males (51.6%). Yearly variation in sex-ratio bias was neither related to density within the colony, nor to global or local oceanographic conditions known to affect both the productivity and accessibility of penguin foraging areas. However, rising sea surface temperature coincided with an increase in fledging sex-ratio variability. Fledging sex ratio was also correlated with difference in body condition between male and female fledglings. When more males were produced in a given year, their body condition was higher (and reciprocally), suggesting that parents might adopt a sex-biased allocation strategy depending on yearly environmental conditions and/or that the effect of environmental parameters on chick condition and survival may be sex-dependent. The initial bias in sex ratio observed at the juvenile stage tended to return to 1∶1 equilibrium upon first breeding attempts, as would be expected from Fisher's classic theory of offspring sex-ratio variation.

Change in schistosome sex ratio under the influence of a biotic environmental-related factor.

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Moné, H

1997-04-01

Schistosoma mansoni is a dioecious trematode responsible for intestinal schistosomiasis in man. The sex ratio was determined for S. mansoni adults derived from cercariae obtained from infected Biomphalaria glabrata maintained in the presence of the nonvector molluse. Marisa cornuarietis. The presence of M. cornuarietis is responsible for enhanced growth of B. glabrata and for a change in the sex ratio of the schistosome, which becomes more male-biased as compared to control snails maintained in aquaria lacking M. cornuarietis. This is the first time the presence of another species in the environment has been shown to influence schistosome sex ratios. Two nonexclusive hypotheses are proposed to explain this variation in the sex ratio: sexual competition between male and female sporocysts; and sex reversal.

Demographic origins of skewed operational and adult sex ratios: perturbation analyses of two-sex models.

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Veran, Sophie; Beissinger, Steven R

2009-02-01

Skewed sex ratios - operational (OSR) and Adult (ASR) - arise from sexual differences in reproductive behaviours and adult survival rates due to the cost of reproduction. However, skewed sex-ratio at birth, sex-biased dispersal and immigration, and sexual differences in juvenile mortality may also contribute. We present a framework to decompose the roles of demographic traits on sex ratios using perturbation analyses of two-sex matrix population models. Metrics of sensitivity are derived from analyses of sensitivity, elasticity, life-table response experiments and life stage simulation analyses, and applied to the stable stage distribution instead of lambda. We use these approaches to examine causes of male-biased sex ratios in two populations of green-rumped parrotlets (Forpus passerinus) in Venezuela. Female local juvenile survival contributed the most to the unbalanced OSR and ASR due to a female-biased dispersal rate, suggesting sexual differences in philopatry can influence sex ratios more strongly than the cost of reproduction.

Sex ratio and Wolbachia infection in the ant Formica exsecta.

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Keller, L; Liautard, C; Reuter, M; Brown, W D; Sundström, L; Chapuisat, M

2001-08-01

Sex allocation data in social Hymenoptera provide some of the best tests of kin selection, parent-offspring conflict and sex ratio theories. However, these studies critically depend on controlling for confounding ecological factors and on identifying all parties that potentially manipulate colony sex ratio. It has been suggested that maternally inherited parasites may influence sex allocation in social Hymenoptera. If the parasites can influence sex allocation, infected colonies are predicted to invest more resources in females than non-infected colonies, because the parasites are transmitted through females but not males. Prime candidates for such sex ratio manipulation are Wolbachia, because these cytoplasmically transmitted bacteria have been shown to affect the sex ratio of host arthropods by cytoplasmic incompatibility, parthenogenesis, male-killing and feminization. In this study, we tested whether Wolbachia infection is associated with colony sex ratio in two populations of the ant Formica exsecta that have been the subject of extensive sex ratio studies. In these populations colonies specialize in the production of one sex or the other. We found that almost all F. exsecta colonies in both populations are infected with Wolbachia. However, in neither population did we find a significant association in the predicted direction between the prevalence of Wolbachia and colony sex ratio. In particular, colonies with a higher proportion of infected workers did not produce more females. Hence, we conclude that Wolbachia does not seem to alter the sex ratio of its hosts as a means to increase transmission rate in these two populations of ants.

Sex ratio at birth and mortality rates are negatively related in humans.

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Madhukar Shivajirao Dama

Full Text Available Evolutionary theory posits that resource availability and parental investment ability could signal offspring sex selection, in order to maximize reproductive returns. Non-human studies have provided evidence for this phenomenon, and maternal condition around the time of conception has been identified as most important factor that influence offspring sex selection. However, studies on humans have reported inconsistent results, mostly due to use of disparate measures as indicators of maternal condition. In the present study, the cross-cultural differences in human natal sex ratio were analyzed with respect to indirect measures of condition namely, life expectancy and mortality rate. Multiple regression modeling suggested that mortality rates have distinct predictive power independent of cross-cultural differences in fertility, wealth and latitude that were earlier shown to predict sex ratio at birth. These findings suggest that sex ratio variation in humans may relate to differences in parental and environmental conditions.

Sex ratio selection and multi-factorial sex determination in the housefly : A dynamic model

NARCIS (Netherlands)

Kozielska, M.A.; Pen, I.R.; Beukeboom, L.W.; Weissing, F.J.

Sex determining (SD) mechanisms are highly variable between different taxonomic groups and appear to change relatively quickly during evolution. Sex ratio selection could be a dominant force causing such changes. We investigate theoretically the effect of sex ratio selection on the dynamics of a

Abnormal sex ratios in human populations: causes and consequences.

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Hesketh, Therese; Xing, Zhu Wei

2006-09-05

In the absence of manipulation, both the sex ratio at birth and the population sex ratio are remarkably constant in human populations. Small alterations do occur naturally; for example, a small excess of male births has been reported to occur during and after war. The tradition of son preference, however, has distorted these natural sex ratios in large parts of Asia and North Africa. This son preference is manifest in sex-selective abortion and in discrimination in care practices for girls, both of which lead to higher female mortality. Differential gender mortality has been a documented problem for decades and led to reports in the early 1990s of 100 million "missing women" across the developing world. Since that time, improved health care and conditions for women have resulted in reductions in female mortality, but these advances have now been offset by a huge increase in the use of sex-selective abortion, which became available in the mid-1980s. Largely as a result of this practice, there are now an estimated 80 million missing females in India and China alone. The large cohorts of "surplus" males now reaching adulthood are predominantly of low socioeconomic class, and concerns have been expressed that their lack of marriageability, and consequent marginalization in society, may lead to antisocial behavior and violence, threatening societal stability and security. Measures to reduce sex selection must include strict enforcement of existing legislation, the ensuring of equal rights for women, and public awareness campaigns about the dangers of gender imbalance.

Sex, sex-ratios, and the dynamics of pelagic copepod populations

DEFF Research Database (Denmark)

Kiørboe, Thomas

2006-01-01

equal adult sex ratios in field populations. Winter population densities are orders of magnitude less than the critical population density required for population persistence, but populations survive winter seasons as resting eggs in the sediment. Population growth in these species is potentially high...... because they have on average a factor of 2 higher egg production rates than other pelagic copepods. Secondly, other copepods require only one mating to stay fertile, and populations of these species have strongly female-skewed adult sex-ratios in field populations. Resting eggs have not been described...

Getting past nature as a guide to the human sex ratio.

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Murphy, Timothy F

2013-05-01

Sex selection of children by pre-conception and post-conception techniques remains morally controversial and even illegal in some jurisdictions. Among other things, some critics fear that sex selection will distort the sex ratio, making opposite-sex relationships more difficult to secure, while other critics worry that sex selection will tilt some nations toward military aggression. The human sex ratio varies depending on how one estimates it; there is certainly no one-to-one correspondence between males and females either at birth or across the human lifespan. Complications about who qualifies as 'male' and 'female' complicate judgments about the ratio even further. Even a judiciously estimated sex ratio does not have, however, the kind of normative status that requires society to refrain from antenatal sex selection. Some societies exhibit lopsided sex ratios as a consequence of social policies and practices, and pragmatic estimates of social needs are a better guide to what the sex ratio should be, as against looking to 'nature'. The natural sex ratio cannot be a sound moral basis for prohibiting parents from selecting the sex of their children, since it ultimately lacks any normative meaning for social choices. © 2011 Blackwell Publishing Ltd.

Mother's occupation and sex ratio at birth

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Amiot Volodymyr

2010-05-01

Full Text Available Abstract Background Many women are working outside of the home, occupying a multitude of jobs with varying degrees of responsibilities and levels of psychological stress. We investigated whether different job types in women are associated with child sex at birth, with the hypothesis that women in job types, which are categorized as "high psychological stress" jobs, would be more likely to give birth to a daughter than a son, as females are less vulnerable to unfavourable conditions during conception, pregnancy and after parturition, and are less costly to carry to term. Methods We investigated the effects of mother's age, maternal and paternal job type (and associated psychological stress levels and paternal income on sex ratio at birth. Our analyses were based on 16,384 incidences of birth from a six-year (2000 to 2005 inclusive childbirth dataset from Addenbrooke's Hospital in Cambridge, UK. We obtained a restricted data set from Addenbrooke's hospital with: maternal age, maternal and paternal occupations, and whether or not the child was first-born. Results Women in job types that were categorized as "high stress" were more likely to give birth to daughters, whereas women in job types that were categorized as "low stress" had equal sex ratios or a slight male bias in offspring. We also investigated whether maternal age, and her partner's income could be associated with reversed offspring sex ratio. We found no association between mother's age, her partner's job stress category or partner income on child sex. However, there was an important interaction between job stress category and partner income in some of the analyses. Partner income appears to attenuate the association between maternal job stress and sex ratios at moderate-income levels, and reverse it at high-income levels. Conclusions To our knowledge this is the first report on the association between women's job type stress categories and offspring sex ratio in humans, and the

Exploring the possibilities for stabilizing the sex ratio in India

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Saurabh RamBihariLal Shrivastava

2015-12-01

Full Text Available The sex ratio is an important demographic indicator for a nation. A wide range of adverse social consequences have been observed because of a skewed sex ratio in India. If India as a nation is to achieve the Millennium Development Goal – 3 (which promotes gender equality and ensures the empowerment of women, the primary target should be involve all those involved, so that a collective and comprehensive approach can be developed to counter the public health menace of an asymmetrical sex ratio. In conclusion, the nation’s program managers should prioritize the issue of a skewed sex ratio and work towards developing a coordinated response.Key Words: Sex ratio, policy makers, India.

Maternal condition but not corticosterone is linked to offspring sex ratio in a passerine bird.

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Lindsay J Henderson

Full Text Available There is evidence of offspring sex ratio adjustment in a range of species, but the potential mechanisms remain largely unknown. Elevated maternal corticosterone (CORT is associated with factors that can favour brood sex ratio adjustment, such as reduced maternal condition, food availability and partner attractiveness. Therefore, the steroid hormone has been suggested to play a key role in sex ratio manipulation. However, despite correlative and causal evidence CORT is linked to sex ratio manipulation in some avian species, the timing of adjustment varies between studies. Consequently, whether CORT is consistently involved in sex-ratio adjustment, and how the hormone acts as a mechanism for this adjustment remains unclear. Here we measured maternal baseline CORT and body condition in free-living blue tits (Cyanistes caeruleus over three years and related these factors to brood sex ratio and nestling quality. In addition, a non-invasive technique was employed to experimentally elevate maternal CORT during egg laying, and its effects upon sex ratio and nestling quality were measured. We found that maternal CORT was not correlated with brood sex ratio, but mothers with elevated CORT fledged lighter offspring. Also, experimental elevation of maternal CORT did not influence brood sex ratio or nestling quality. In one year, mothers in superior body condition produced male biased broods, and maternal condition was positively correlated with both nestling mass and growth rate in all years. Unlike previous studies maternal condition was not correlated with maternal CORT. This study provides evidence that maternal condition is linked to brood sex ratio manipulation in blue tits. However, maternal baseline CORT may not be the mechanistic link between the maternal condition and sex ratio adjustment. Overall, this study serves to highlight the complexity of sex ratio adjustment in birds and the difficulties associated with identifying sex biasing mechanisms.

Patterns of Family Formation in Response to Sex Ratio Variation.

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Schacht, Ryan; Kramer, Karen L

2016-01-01

The impact that unbalanced sex ratios have on health and societal outcomes is of mounting contemporary concern. However, it is increasingly unclear whether it is male- or female-biased sex ratios that are associated with family and social instability. From a socio-demographic perspective, male-biased sex ratios leave many men unable to find a mate, elevating competition among males, disrupting family formation and negatively affecting social stability. In contrast, from a mating-market perspective, males are expected to be less willing to marry and commit to a family when the sex ratio is female-biased and males are rare. Here we use U.S. data to evaluate predictions from these competing frameworks by testing the relationship between the adult sex ratio and measures of family formation. We find that when women are rare men are more likely to marry, be part of a family and be sexually committed to a single partner. Our results do not support claims that male-biased sex ratios lead to negative family outcomes due to a surplus of unmarried men. Rather, our results highlight the need to pay increased attention to female-biased sex ratios.

A study to review sex ratio at birth and analyze preferences for the sex of the unborn.

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Warade, Yugali; Balsarkar, Geetha; Bandekar, Pooja

2014-02-01

(1) To study the status of sex ratio at birth with increasing birth order, (2) To ascertain the relationship of declining sex ratio with respect to socio demographic factors. (3) To study outlook of patient towards sex preference, willingness to determine sex of the fetus, wish to terminate the pregnancy in case of unwanted sex of the baby. This is the retrospective study done in the Department of Obstetrics and Gynaecology, Nowrosjee Wadia Maternity Hospital, Parel, Mumbai. The data was collected from the records maintained in Medical Record Department from January 2007 to December 2012 and were studied to determine the sex ratio as well as its relationship with the increasing parity. 95 % confidence interval for the sex ratios was calculated. Average sex ratio of 6 years was 908 females per 1,000 males. Sex ratio was 972 females per 1,000 males in primi para, which decreased to 879 females per 1,000 males in second para, further reduced to 784 females per 1,000 males in third para and 864 females per 1,000 males in fourth para. The 'sex ratio at birth', defined as the number of girls born for every 1,000 boys born, is a more accurate and refined indicator of the extent of prenatal sex selection.

Psychological distress during early gestation and offspring sex ratio

DEFF Research Database (Denmark)

Obel, C; Henriksen, TB; Secher, Niels Jørgen

2007-01-01

BACKGROUND: Exposure to severe stress in early pregnancy is associated with a lower male to female ratio (sex ratio), but whether more moderate levels of psychological discomfort have the same kind of effect is unknown. In a population based follow-up study, we aimed to test whether psychological...... suggest that not only severe stress, but also more moderate and common levels of psychological distress, may decrease the sex ratio in the offspring. Stress during pregnancy is a likely candidate involved in the decreasing sex ratio observed in many countries....... distress was associated with the sex ratio in the offspring. METHODS: From 1989 to 1992, a cohort of 8,719 Danish-speaking pregnant women were followed until delivery. Questionnaires were administered to the women in early pregnancy and 6,629 (76%) completed the 30-item version of the General Health...

Psychological distress during early gestation and offspring sex ratio

DEFF Research Database (Denmark)

Obel, Carsten; Henriksen, Tine Brink; Secher, Niels Jørgen

2007-01-01

BACKGROUND: Exposure to severe stress in early pregnancy is associated with a lower male to female ratio (sex ratio), but whether more moderate levels of psychological discomfort have the same kind of effect is unknown. In a population based follow-up study, we aimed to test whether psychological...... suggest that not only severe stress, but also more moderate and common levels of psychological distress, may decrease the sex ratio in the offspring. Stress during pregnancy is a likely candidate involved in the decreasing sex ratio observed in many countries. Udgivelsesdato: 2007-Nov...... distress was associated with the sex ratio in the offspring. METHODS: From 1989 to 1992, a cohort of 8,719 Danish-speaking pregnant women were followed until delivery. Questionnaires were administered to the women in early pregnancy and 6,629 (76%) completed the 30-item version of the General Health...

Meiotic sex ratio variation in natural populations of Ceratodon purpureus (Ditrichaceae).

Science.gov (United States)

Norrell, Tatum E; Jones, Kelly S; Payton, Adam C; McDaniel, Stuart F

2014-09-01

• Sex ratio variation is a common but often unexplained phenomenon in species across the tree of life. Here we evaluate the hypothesis that meiotic sex ratio variation can contribute to the biased sex ratios found in natural populations of the moss Ceratodon purpureus.• We obtained sporophytes from several populations of C. purpureus from eastern North America. From each sporophyte, we estimated the mean spore viability by germinating replicate samples on agar plates. We estimated the meiotic sex ratio of each sporophyte by inferring the sex of a random sample of germinated spores (mean = 77) using a PCR-RFLP test. We tested for among-sporophyte variation in viability using an ANOVA and for deviations from 1:1 sex ratio using a χ(2)-test and evaluated the relationship between these quantities using a linear regression.• We found among-sporophyte variation in spore viability and meiotic sex ratio, suggesting that genetic variants that contribute to variation in both of these traits segregate within populations of this species. However, we found no relationship between these quantities, suggesting that factors other than sex ratio distorters contribute to variation in spore viability within populations.• These results demonstrate that sex ratio distortion may partially explain the population sex ratio variation seen in C. purpureus, but more generally that genetic conflict over meiotic segregation may contribute to fitness variation in this species. Overall, this study lays the groundwork for future studies on the genetic basis of meiotic sex ratio variation. © 2014 Botanical Society of America, Inc.

[The sex ratio at birth: a retrospective review and commentary].

Science.gov (United States)

Aubenque, M

1989-01-01

Trends in the sex ratio are examined, and the possible effect of new biotechnologies on sex preselection is discussed. "We recall that this ratio is very stable, around 105 males for 100 females (live births). However, in France, a slight decreasing trend during the 19th century can be observed (from 107 to 104). At the present time this ratio seems to be maintained at a level of 105.3. The great demographic perturbations, particularly caused by wars, have been marked by a slight but notable increase in the indicator (106) when natality rises again after a deep depression. The variations, always small, of this indicator are more dependent on the male than on female natality, for reasons that are unclear." A comment by Paul Damiani is included (pp. 99-102). (SUMMARY IN ENG) excerpt

Pengaruh Sex Ratio Ayam Arab Terhadap Fertilitas, Daya Tetas, Dan Bobot Tetas

OpenAIRE

Widi Astomo; Dian Septinova; Tintin Kurtini

2016-01-01

This study aimed to determine (1) This effect of sex ratio arabic chicken on fertility, hatchibility , and doc weight and (2) to determine the best sex ratio of effect arabic chicken on fertility, hatchability, and doc weight. This study was conducted in August 2015 at Tegalrejo village, Gadingrejo districk, Pringsewu regency.The research use 144 arabic chicken consisted of 18 males and 126 females. This research use the complete randomized design with 3 treatments and 6 times replications...

Sex ratios in fetuses and liveborn infants with autosomal aneuploidy

Energy Technology Data Exchange (ETDEWEB)

Heuther, C.A.; Martin, R.L.M.; Stoppelman, S.M. [Univ. of Cincinnati, OH (United States)] [and others

1996-06-14

Ten data sources were used substantially to increase the available data for estimating fetal and livebirth sex ratios for Patau (trisomy 13), Edwards (trisomy 18), and Down (trisomy 21) syndromes and controls. The fetal sex ratio estimate was 0.88 (N = 584) for trisomy 13, 0.90 (N = 1702) for trisomy 18, and 1.16 (N = 3154) for trisomy 21. All were significantly different from prenatal controls (1.07). The estimated ratios in prenatal controls were 1.28 (N = 1409) for CVSs and 1.06 (N = 49427) for amniocenteses, indicating a clear differential selection against males, mostly during the first half of fetal development. By contrast, there were no sex ratio differences for any of the trisomies when comparing gestational ages <16 and >16 weeks. The livebirth sex ratio estimate was 0.90 (N = 293) for trisomy 13, 0.63 (N = 497) for trisomy 18, and 1.15 (N = 6424) for trisomy 21, the latter two being statistically different than controls (1.05) (N = 3660707). These ratios for trisomies 13 and 18 were also statistically different than the ratio for trisomy 21. Only in trisomy 18 did the sex ratios in fetuses and livebirths differ, indicating a prenatal selection against males >16 weeks. No effects of maternal age or race were found on these estimates for any of the fetal or livebirth trisomies. Sex ratios for translocations and mosaics were also estimated for these aneuploids. Compared to previous estimates, these results are less extreme, most likely because of larger sample sizes and less sample bias. They support the hypothesis that these trisomy sex ratios are skewed at conception, or become so during embryonic development through differential intrauterine selection. The estimate for Down syndrome livebirths is also consistent with the hypothesis that its higher sex ratio is associated with paternal nondisjunction. 36 refs., 5 tabs.

Differential timing and latitudinal variation in sex ratio of Aquatic Warblers during the autumn migration

Science.gov (United States)

Wojczulanis-Jakubas, Katarzyna; Chrostek, Małgorzata E.; Jiguet, Frédéric; Martínez, Carlos Zumalacárregui; Miguélez, David; Neto, Júlio M.

2017-12-01

Differential migration has been extensively reported in spring, but less so in autumn, particularly in relation to sex in monomorphic bird species. Here, we analysed the autumn passage of a monomorphic, globally threatened passerine, the Aquatic Warbler Acrocephalus paludicola throughout Western Europe, with regard to age and sex. We showed that, overall, adults migrated earlier than first-year birds, and males migrated earlier than females during the autumn migration. This may be caused by an overall social dominance of adults over immatures, and differentiated migration strategy of males and females. In addition, we found male-skewed sex proportions, with a tendency to an equalised ratio in more southern stopover sites. This may indicate a male bias in the global population or different migration strategies of the sexes. Differential migration may cause the age and sex classes to be exposed differently to various threats affecting demographic structure of the species.

Parental correlates of offspring sex ratio in Eurasian Oystercatchers

NARCIS (Netherlands)

Heg, D.; Dingemanse, NJ; Lessells, CM; Mateman, AC

2000-01-01

We investigated hatchling and fledgling sex ratios in Eurasian Oystercatchers (Haematopus ostralegus) using random amplified polymorphic DNA markers. The overall hatchling (53% males, n = 374 hatchlings from 177 broods) and fledgling (49% males, n = 51) sex ratio did not differ significantly from

Population sex ratios: another consideration in the reintroduction - reinforcement debate?

Directory of Open Access Journals (Sweden)

Sergio A Lambertucci

Full Text Available Reintroduction or reinforcement (RorR of wild populations is a common conservation strategy. Many conservation projects involve the release of individuals of poorly studied species. This may lead to inefficient results or negative impacts on the conservation efforts. Here, we provide new insights into the conservation implications and potential consequences of a skew in the sex ratio of released birds and of the number of birds supplemented for the demography of a long-lived dimorphic bird species, the Andean condor (Vulturgryphus. We demonstrate that a RorR conservation program may be less effective in conserving a species if the sex ratios of the releases and the recipient populations are not considered. We also show that releases can reduce population declines but only if carried out over long periods (i.e., several decades. This can mean high costs for release programs and the added challenge of maintaining programs over time. If RorR programs are to be implemented, bearing in mind the importance of properly assessing their effectiveness, we urge conservation researchers and managers to consider the implications of sex ratio biases for wild populations, and particularly for dimorphic species with sexually despotic behaviour.

Maintaining access to safe abortion and reducing sex ratio imbalances in Asia.

Science.gov (United States)

Ganatra, Bela

2008-05-01

High sex ratios at birth (108 boys to 100 girls or higher) are seen in China, Taiwan, South Korea and parts of India and Viet Nam. The imbalance is the result of son preference, accentuated by declining fertility. Prenatal sex detection with ultrasound followed by second trimester abortion is one of the ways sex selection manifests itself, but it is not the causative factor. Advocates and governments seeking to reverse this imbalance have largely prohibited sex detection tests and/or sex selective abortion, assuming these measures would reverse the trend. Such policies have been difficult to enforce and have met with only limited success. At the same time, such policies are starting to have adverse effects on the already limited access to safe and legal second trimester abortion for reasons other than sex selection. Moreover, the sex selection issue is being used as a platform for anti-abortion rhetoric by certain groups. Maintaining access to safe abortion and achieving a decline in high sex ratios are both important goals. Both are possible if the focus shifts to addressing the conditions that drive son preference.

National, regional, and global sex ratios of infant, child, and under-5 mortality and identification of countries with outlying ratios: a systematic assessment.

Science.gov (United States)

Alkema, Leontine; Chao, Fengqing; You, Danzhen; Pedersen, Jon; Sawyer, Cheryl C

2014-09-01

Under natural circumstances, the sex ratio of male to female mortality up to the age of 5 years is greater than one but sex discrimination can change sex ratios. The estimation of mortality by sex and identification of countries with outlying levels is challenging because of issues with data availability and quality, and because sex ratios might vary naturally based on differences in mortality levels and associated cause of death distributions. For this systematic analysis, we estimated country-specific mortality sex ratios for infants, children aged 1-4 years, and children under the age of 5 years (under 5s) for all countries from 1990 (or the earliest year of data collection) to 2012 using a Bayesian hierarchical time series model, accounting for various data quality issues and assessing the uncertainty in sex ratios. We simultaneously estimated the global relation between sex ratios and mortality levels and constructed estimates of expected and excess female mortality rates to identify countries with outlying sex ratios. Global sex ratios in 2012 were 1·13 (90% uncertainty interval 1·12-1·15) for infants, 0·95 (0·93-0·97) for children aged 1-5 years, and 1·08 (1·07-1·09) for under 5s, an increase since 1990 of 0·01 (-0·01 to 0·02) for infants, 0·04 (0·02 to 0·06) for children aged 1-4 years, and 0·02 (0·01 to 0·04) for under 5s. Levels and trends varied across regions and countries. Sex ratios were lowest in southern Asia for 1990 and 2012 for all age groups. Highest sex ratios were seen in developed regions and the Caucasus and central Asia region. Decreasing mortality was associated with increasing sex ratios, except at very low infant mortality, where sex ratios decreased with total mortality. For 2012, we identified 15 countries with outlying under-5 sex ratios, of which ten countries had female mortality higher than expected (Afghanistan, Bahrain, Bangladesh, China, Egypt, India, Iran, Jordan, Nepal, and Pakistan). Although excess female

Sex ratio in two species of Pegoscapus wasps (Hymenoptera: Agaonidae) that develop in figs: can wasps do mathematics, or play sex ratio games?

Science.gov (United States)

Ramírez-Benavides, William; Monge-Nájera, Julián; Chavarría, Juan B

2009-09-01

The fig pollinating wasps (Hymenoptera: Agaonidae) have obligate arrhenotoky and a breeding structure that fits local mate competition (LMC). It has been traditionally assumed that LMC organisms adjust the sex ratio by laying a greater proportion of male eggs when there is superparasitism (several foundresses in a host). We tested the assumption with two wasp species, Pegoscapus silvestrii, pollinator of Ficus pertusa and Pegoscapus tonduzi, pollinator of Ficus eximia (= F citrifolia), in the Central Valley of Costa Rica. Total number of wasps and seeds were recorded in individual isolated naturally colonized syconia. There was a constant additive effect between the number of foundresses and the number of males produced in the brood of a syconium, while the number of females decreased. Both wasp species seem to have precise sex ratios and probably lay the male eggs first in the sequence, independently of superparasitism and clutch size: consequently, they have a non-random sex allocation. Each syconium of Ficus pertusa and of F. eximia colonized by one foundress had similar mean numbers of females, males, and seeds. The two species of wasps studied do not seem to adjust the sex ratio when there is superparasitism. Pollinating fig wasp behavior is better explained by those models not assuming that females do mathematical calculations according to other females' sex ratios, size, number of foundresses, genetic constitution, clutch size or environmental conditions inside the syconium. Our results are in agreement with the constant male number hypothesis, not with sex ratio games.

A heritable component in sex ratio and caste determination in a Cardiocondyla ant

Directory of Open Access Journals (Sweden)

Heinze Jürgen

2009-10-01

Full Text Available Abstract Studies on sex ratios in social insects provide among the most compelling evidence for the importance of kin selection in social evolution. The elegant synthesis of Fisher's sex ratio principle and Hamilton's inclusive fitness theory predicts that colony-level sex ratios vary with the colonies' social and genetic structures. Numerous empirical studies in ants, bees, and wasps have corroborated these predictions. However, the evolutionary optimization of sex ratios requires genetic variation, but one fundamental determinant of sex ratios - the propensity of female larvae to develop into young queens or workers ("queen bias" - is thought to be largely controlled by the environment. Evidence for a genetic influence on sex ratio and queen bias is as yet restricted to a few taxa, in particular hybrids. Because of the very short lifetime of their queens, ants of the genus Cardiocondyla are ideal model systems for the study of complete lifetime reproductive success, queen bias, and sex ratios. We found that lifetime sex ratios of the ant Cardiocondyla kagutsuchi have a heritable component. In experimental single-queen colonies, 22 queens from a genetic lineage with a highly female-biased sex ratio produced significantly more female-biased offspring sex ratios than 16 queens from a lineage with a more male-biased sex ratio (median 91.5% vs. 58.5% female sexuals. Sex ratio variation resulted from different likelihood of female larvae developing into sexuals (median 50% vs. 22.6% female sexuals even when uniformly nursed by workers from another colony. Consistent differences in lifetime sex ratios and queen bias among queens of C. kagutsuchi suggest that heritable, genetic or maternal effects strongly affect caste determination. Such variation might provide the basis for adaptive evolution of queen and worker strategies, though it momentarily constrains the power of workers and queens to optimize caste ratios.

A heritable component in sex ratio and caste determination in a Cardiocondyla ant.

Science.gov (United States)

Frohschammer, Sabine; Heinze, Jürgen

2009-10-28

Studies on sex ratios in social insects provide among the most compelling evidence for the importance of kin selection in social evolution. The elegant synthesis of Fisher's sex ratio principle and Hamilton's inclusive fitness theory predicts that colony-level sex ratios vary with the colonies' social and genetic structures. Numerous empirical studies in ants, bees, and wasps have corroborated these predictions. However, the evolutionary optimization of sex ratios requires genetic variation, but one fundamental determinant of sex ratios - the propensity of female larvae to develop into young queens or workers ("queen bias") - is thought to be largely controlled by the environment. Evidence for a genetic influence on sex ratio and queen bias is as yet restricted to a few taxa, in particular hybrids.Because of the very short lifetime of their queens, ants of the genus Cardiocondyla are ideal model systems for the study of complete lifetime reproductive success, queen bias, and sex ratios. We found that lifetime sex ratios of the ant Cardiocondyla kagutsuchi have a heritable component. In experimental single-queen colonies, 22 queens from a genetic lineage with a highly female-biased sex ratio produced significantly more female-biased offspring sex ratios than 16 queens from a lineage with a more male-biased sex ratio (median 91.5% vs. 58.5% female sexuals). Sex ratio variation resulted from different likelihood of female larvae developing into sexuals (median 50% vs. 22.6% female sexuals) even when uniformly nursed by workers from another colony.Consistent differences in lifetime sex ratios and queen bias among queens of C. kagutsuchi suggest that heritable, genetic or maternal effects strongly affect caste determination. Such variation might provide the basis for adaptive evolution of queen and worker strategies, though it momentarily constrains the power of workers and queens to optimize caste ratios.

Recurrent selection on the Winters sex-ratio genes in Drosophila simulans.

Science.gov (United States)

Kingan, Sarah B; Garrigan, Daniel; Hartl, Daniel L

2010-01-01

Selfish genes, such as meiotic drive elements, propagate themselves through a population without increasing the fitness of host organisms. X-linked (or Y-linked) meiotic drive elements reduce the transmission of the Y (X) chromosome and skew progeny and population sex ratios, leading to intense conflict among genomic compartments. Drosophila simulans is unusual in having a least three distinct systems of X chromosome meiotic drive. Here, we characterize naturally occurring genetic variation at the Winters sex-ratio driver (Distorter on the X or Dox), its progenitor gene (Mother of Dox or MDox), and its suppressor gene (Not Much Yang or Nmy), which have been previously mapped and characterized. We survey three North American populations as well as 13 globally distributed strains and present molecular polymorphism data at the three loci. We find that all three genes show signatures of selection in North America, judging from levels of polymorphism and skews in the site-frequency spectrum. These signatures likely result from the biased transmission of the driver and selection on the suppressor for the maintenance of equal sex ratios. Coalescent modeling indicates that the timing of selection is more recent than the age of the alleles, suggesting that the driver and suppressor are coevolving under an evolutionary "arms race." None of the Winters sex-ratio genes are fixed in D. simulans, and at all loci we find ancestral alleles, which lack the gene insertions and exhibit high levels of nucleotide polymorphism compared to the derived alleles. In addition, we find several "null" alleles that have mutations on the derived Dox background, which result in loss of drive function. We discuss the possible causes of the maintenance of presence-absence polymorphism in the Winters sex-ratio genes.

Sex ratio at birth in India, its relation to birth order, sex of previous children and use of indigenous medicine.

Directory of Open Access Journals (Sweden)

Samiksha Manchanda

Full Text Available OBJECTIVE: Sex-ratio at birth in families with previous girls is worse than those with a boy. Our aim was to prospectively study in a large maternal and child unit sex-ratio against previous birth sex and use of traditional medicines for sex selection. MAIN OUTCOME MEASURES: Sex-ratio among mothers in families with a previous girl and in those with a previous boy, prevalence of indigenous medicine use and sex-ratio in those using medicines for sex selection. RESULTS: Overall there were 806 girls to 1000 boys. The sex-ratio was 720:1000 if there was one previous girl and 178:1000 if there were two previous girls. In second children of families with a previous boy 1017 girls were born per 1000 boys. Sex-ratio in those with one previous girl, who were taking traditional medicines for sex selection, was 928:1000. CONCLUSION: Evidence from the second children clearly shows the sex-ratio is being manipulated by human interventions. More mothers with previous girls tend to use traditional medicines for sex selection, in their subsequent pregnancies. Those taking such medication do not seem to be helped according to expectations. They seem to rely on this method and so are less likely use more definitive methods like sex selective abortions. This is the first such prospective investigation of sex ratio in second children looked at against the sex of previous children. More studies are needed to confirm the findings.

Maternal preconception diet and the sex ratio

NARCIS (Netherlands)

Cramer, J.S.; Lumey, L.H.

2009-01-01

Temporal variations in the sex ratio or the ratio of boys over girls at birth have been widely studied and variously attributed to social changes, conditions of war, and environmental changes. Recently, Mathews, Johnson and Neil (2008) studied the direct evidence of individual pregnancies and

Sex ratio in two species of Pegoscapus wasps (Hymenoptera: Agaonidae that develop in figs: can wasps do mathematics, or play sex ratio games?

Directory of Open Access Journals (Sweden)

William Ramírez-Benavides

2009-09-01

Full Text Available The fig pollinating wasps (Hymenoptera: Agaonidae have obligate arrhenotoky and a breeding structure that fits local mate competition (LMC. It has been traditionally assumed that LMC organisms adjust the sex ratio by laying a greater proportion of male eggs when there is superparasitism (several foundresses in a host. We tested the assumption with two wasp species, Pegoscapus silvestrii, pollinator of Ficus pertusa and Pegoscapus tonduzi, pollinator of Ficus eximia (= F. citrifolia, in the Central Valley of Costa Rica. Total number of wasps and seeds were recorded in individual isolated naturally colonized syconia. There was a constant additive effect between the number of foundresses and the number of males produced in the brood of a syconium, while the number of females decreased. Both wasp species seem to have precise sex ratios and probably lay the male eggs first in the sequence, independently of superparasitism and clutch size: consequently, they have a non-random sex allocation. Each syconium of Ficus pertusa and of F. eximia colonized by one foundress had similar mean numbers of females, males, and seeds. The two species of wasps studied do not seem to adjust the sex ratio when there is superparasitism. Pollinating fig wasp behavior is better explained by those models not assuming that females do mathematical calculations according to other females’ sex ratios, size, number of foundresses, genetic constitution, clutch size or environmental conditions inside the syconium. Our results are in agreement with the constant male number hypothesis, not with sex ratio games. Rev. Biol. Trop. 57 (3: 605-621. Epub 2009 September 30.

Maternal preconception diet and the sex ratio

NARCIS (Netherlands)

Cramer, J.S.; Lumey, L.H.

2010-01-01

Temporal variations in the sex ratio, or the ratio of boys to girls at birth, have been widely studied and variously attributed to social changes, conditions of war, and environmental changes. Recently, Mathews et al. ["You are what your mother eats: Evidence for maternal preconception diet

Sex ratio, gonadal development and fecundity of the grunt ...

African Journals Online (AJOL)

The sex ratio, gonadosomatic index, stages of gonadal development and fecundity of the grunt, Pomadasys jubelini in the New Calabar-Bonny River were investigated. P. jubelini had a sex ratio of 1: 2.1 (male to female). Gonadosomatic index ranged from 0.33 to 7.29% with a mean of 2.89+0.08%. High gonadosomatic ...

Neither Biased Sex Ratio nor Spatial Segregation of the Sexes in the Subtropical Dioecious Tree Eurycorymbus cavaleriei (Sapindaceae)

Institute of Scientific and Technical Information of China (English)

Pu-xin Gao; Ming Kang; Jing Wang; Qi-gang Ye; Hong-wen Huang

2009-01-01

Knowledge of sex ratio and spatial distribution of males and females of dioecious species is both of evolutionary interest and of crucial importance for biological conservation. Eurycorymbus cavaleriei, the only species in the genus Eurycorymbus (Saplndaceae), is a dioecious tree endemic to subtropical montane forest in South China. Sex ratios were investigated in 15 natural populations for the two defined ages (young and old). Spatial distribution of males and females was further studied in six large populations occurring in different habitats (fragmented and continuous). The study revealed a slight trend of malebiased sex ratio in both ages of E. cavaleriei, but sex ratio of most populations (13 out of 15) did not display statistically significant deviation from equality. All of the four significantly male-biased populations in the young class shifted to equality or even female-biased. The Ripley's K analysis of the distribution of males with respect to females suggested that individuals of the opposite sexes were more randomly distributed rather than spatially structured. These results suggest that the male-biased sex ratio in E. cavaleriei may result from the precocity of males and habitat heterogeneity. The sex ratio and the sex spatial distribution pattern are unlikely to constitute a serious threat to the survival of the species.

Lunar cycles at mating do not influence sex ratio at birth in horses.

Science.gov (United States)

Aguilar, J J; Cuervo-Arango, J; Santa Juliana, L

2015-02-01

It is scientifically demonstrated that lunar cycles have important effects on several biological events. Controversy exists about the lunar influence on human and animal parturition. In addition, in the horse industry, especially in Polo Horse breeders of Argentina and around the world there is a higher demand for female offspring than for males. The objective of this study was to determine whether there is a significant association between the lunar phase at the time of mating and the sex ratio at birth in horses. The Argentinean Stud Book provided information related to all matings registered for Thoroughbred and Arab horses between 2003 and 2011. Statistical associations were tested between dates of matings at different lunar phases or days and sex ratio at birth. A total of 65.535 gestations were studied. Overall, sex ratio at birth resulted in 33.396 fillies (50.96%) and 32.139 colts (49.04%). The percentages of males and females at birth were not statistically different amongst the different lunar phases or days. We can strongly conclude that managing the breeding dates in relation to lunar cycles in order to manipulate the sex ratio of the offspring is not a viable option in horses.

Determining sex ratios of turtle hatchlings

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Previous status assessments of marine turtles have assumed that the natural sex ratio of a marine turtle population is 1:1 (e.g. Conant et al. 2009). However, this...

Live birth sex ratios and father's geographic origins in Jerusalem, 1964-1976.

Science.gov (United States)

Groeger, J; Opler, M; Kleinhaus, K; Perrin, M C; Calderon-Margalit, R; Manor, O; Paltiel, O; Conley, D; Harlap, S; Malaspina, D

2017-05-06

To examine whether ancestry influenced sex ratios of offspring in a birth cohort before parental antenatal sex selection influenced offspring sex. We measured the sex ratio as the percent of males according to countries of birth of paternal and maternal grandfathers in 91,459 live births from 1964 to 1976 in the Jerusalem Perinatal Study. Confidence limits (CI) were computed based on an expected sex ratio of 1.05, which is 51.4% male. Of all live births recorded, 51.4% were male. Relative to Jewish ancestry (51.4% males), significantly more males (1,761) were born to Muslim ancestry (54.5, 95% CI = 52.1-56.8, P = 0.01). Among the former, sex ratios were not significantly associated with paternal or maternal age, education, or offspring's birth order. Consistent with a preference for male offspring, the sex ratio decreased despite increasing numbers of births over the 13-year period. Sex ratios were not affected by maternal or paternal origins in North Africa or Europe. However, the offspring whose paternal grandfathers were born in Western Asia included fewer males than expected (50.7, 50.1-51.3, P = 0.02), whether the father was born abroad (50.7) or in Israel (50.8). This was observed for descendents of paternal grandfathers born in Lebanon (47.6), Turkey (49.9), Yemen & Aden (50.2), Iraq (50.5), Afghanistan (50.5), Syria (50.6), and Cyprus (50.7); but not for those from India (51.5) or Iran (51.9). The West Asian group showed the strongest decline in sex ratios with increasing paternal family size. A decreased sex ratio associated with ancestry in Western Asia is consistent with reduced ability to bear sons by a subset of Jewish men in the Jerusalem cohort. Lower sex ratios may be because of pregnancy stress, which may be higher in this subgroup. Alternatively, a degrading Y chromosome haplogroup or other genetic or epigenetic differences on male germ lines could affect birth ratios, such as differential exposure to an environmental agent, dietary

Relationship Formation and Stability in Emerging Adulthood: Do Sex Ratios Matter?

Science.gov (United States)

Warner, Tara D.; Manning, Wendy D.; Giordano, Peggy C.; Longmore, Monica A.

2011-01-01

Research links sex ratios with the likelihood of marriage and divorce. However, whether sex ratios similarly influence precursors to marriage (transitions in and out of dating or cohabiting relationships) is unknown. Utilizing data from the Toledo Adolescent Relationships Study and the 2000 U.S. Census, this study assesses whether sex ratios…

Adult sex ratio variation : Implications for breeding system evolution

NARCIS (Netherlands)

Szekely, T.; Weissing, F. J.; Komdeur, J.

Adult sex ratio (ASR) exhibits immense variation in nature, although neither the causes nor the implications of this variation are fully understood. According to theory, the ASR is expected to influence sex roles and breeding systems, as the rarer sex in the population has more potential partners to

Sibling sex ratio of individuals diagnosed with autism spectrum disorder as children

DEFF Research Database (Denmark)

Mouridsen, Svend Erik; Rich, Bente; Isager, Torben

2010-01-01

AIM: To study the sex ratio (proportion of males) in siblings of individuals diagnosed with autism spectrum disorders (ASDs) as children. METHOD: In the current study, we extended previous studies dealing with the androgen theory of autism and examined sex ratios in the siblings of 326 individuals...... the Danish live-birth sex ratio over the same period (0.514, p=0.001). The sibling sex ratio was not associated with the IQ in the autistic probands. INTERPRETATION: Our findings suggest a potential indirect confirmation of the androgen theory of autism....

The potential pitfalls of studying adult sex ratios at aggregate levels in humans.

Science.gov (United States)

Pollet, Thomas V; Stoevenbelt, Andrea H; Kuppens, Toon

2017-09-19

Human adult sex ratios have been studied extensively across the biological and social sciences. While several studies have examined adult sex ratio effects in a multilevel perspective, many studies have focused on effects at an aggregated level only. In this paper, we review some key issues relating to such analyses. We address not only nation-level analyses, but also aggregation at lower levels, to investigate whether these issues extend to lower levels of aggregation. We illustrate these issues with novel databases covering a broad range of variables. Specifically, we discuss distributional issues with aggregated measures of adult sex ratio, significance testing, and statistical non-independence when using aggregate data. Firstly, we show that there are severe distributional issues with national adult sex ratio, such as extreme cases. Secondly, we demonstrate that many 'meaningless' variables are significantly correlated with adult sex ratio (e.g. the max. elevation level correlates with sex ratio at US state level). Finally, we re-examine associations between adult sex ratios and teenage fertility and find no robust evidence for an association at the aggregate level. Our review highlights the potential issues of using aggregate data on adult sex ratios to test hypotheses from an evolutionary perspective in humans.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'. © 2017 The Author(s).

Recent increase in sex ratio at birth in Viet Nam.

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Christophe Z Guilmoto

Full Text Available INTRODUCTION: Since the 1980s, sex ratio at birth (male births per 100 female births has increased in many Asian countries as a result of selective abortions, but to date there has been no such evidence for Viet Nam. Our aim in this paper is to ascertain the situation with respect to sex ratio at birth in Viet Nam over the past five years. MATERIALS AND METHODS: Original data were obtained from sample population surveys in Viet Nam recording annual birth rates since 2000 of about 450,000 women, as well as from two successive birth surveys conducted for the first time in 2007 (1.1 million births. The annual population surveys include specific information on birth history and mothers' characteristics to be used for the analysis of trends and differentials in sex ratio at birth. RESULTS AND DISCUSSION: Birth history statistics indicate that the SRB in Viet Nam has recorded a steady growth since 2001. Starting from a level probably close to the biological standard of 105, the SRB reached 108 in 2005 and 112 in 2006, a value significantly above the normal level. An independent confirmation of these results comes from the surveys of births in health facilities which yielded a SRB of 110 in 2006-07. High SRB is linked to various factors such as access to modern health care, number of prenatal visits, level of higher education and employment status, young age, province of residence and prenatal sex determination. These results suggest that prenatal sex determination followed by selective abortion has recently become more common in Viet Nam. This recent trend is a consequence of various factors such as preference for sons, declining fertility, easy access to abortion, economic development as well as the increased availability of ultrasonography facilities.

Recent increase in sex ratio at birth in Viet Nam.

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Guilmoto, Christophe Z; Hoàng, Xuyên; Van, Toan Ngo

2009-01-01

Since the 1980s, sex ratio at birth (male births per 100 female births) has increased in many Asian countries as a result of selective abortions, but to date there has been no such evidence for Viet Nam. Our aim in this paper is to ascertain the situation with respect to sex ratio at birth in Viet Nam over the past five years. Original data were obtained from sample population surveys in Viet Nam recording annual birth rates since 2000 of about 450,000 women, as well as from two successive birth surveys conducted for the first time in 2007 (1.1 million births). The annual population surveys include specific information on birth history and mothers' characteristics to be used for the analysis of trends and differentials in sex ratio at birth. Birth history statistics indicate that the SRB in Viet Nam has recorded a steady growth since 2001. Starting from a level probably close to the biological standard of 105, the SRB reached 108 in 2005 and 112 in 2006, a value significantly above the normal level. An independent confirmation of these results comes from the surveys of births in health facilities which yielded a SRB of 110 in 2006-07. High SRB is linked to various factors such as access to modern health care, number of prenatal visits, level of higher education and employment status, young age, province of residence and prenatal sex determination. These results suggest that prenatal sex determination followed by selective abortion has recently become more common in Viet Nam. This recent trend is a consequence of various factors such as preference for sons, declining fertility, easy access to abortion, economic development as well as the increased availability of ultrasonography facilities.

Causes and consequences of adult sex ratio imbalance in a historical U.S. population.

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Schacht, Ryan; Smith, Ken R

2017-09-19

The responsiveness of individuals to partner availability has been well-documented across the literature. However, there is disagreement regarding the direction of the consequences of sex ratio imbalance. Specifically, does an excess of males or females promote male-male mating competition? In an attempt to clarify the role of the adult sex ratio (ASR) on behaviour, here we evaluate both competing and complimentary expectations derived from theory across the social and biological sciences. We use data drawn from a historical, nineteenth century population in North America and target several life-history traits thought to be affected by partner availability: age at first birth, relationship status, completed fertility and longevity. Furthermore, we assess the role of various contributors to a population's ASR. We find that both the contributors to and consequences of sex ratio imbalance vary over time. Our results largely support predictions of greater male pairbond commitment and lesser male mating effort, as well as elevated bargaining power of women in response to female scarcity. After reviewing our findings, and others from across the literature, we highlight the need to adjust predictions in response to ASR imbalance by the: (i) culturally mediated mating arena, (ii) variable role of demographic inputs across time and place, (iii) constraints to behavioural outcomes across populations, and (iv) ability and accuracy of individuals to assess partner availability.This article is part of the themed issue 'Adult sex ratios and reproductive strategies: a critical re-examination of sex differences in human and animal societies'. © 2017 The Author(s).

Working Late: Do Workplace Sex Ratios Affect Partnership Formation and Dissolution?

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Svarer, Michael

2007-01-01

In this paper, I analyze the association between workplace sex ratios and partnership formation and dissolution. I find that the risk of dissolution increases with the fraction of coworkers of the opposite sex at both the female and male workplace. On the other hand, workplace sex ratios are not important for the overall transition rate from…

Going All In: Unfavorable Sex Ratios Attenuate Choice Diversification.

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Ackerman, Joshua M; Maner, Jon K; Carpenter, Stephanie M

2016-06-01

When faced with risky decisions, people typically choose to diversify their choices by allocating resources across a variety of options and thus avoid putting "all their eggs in one basket." The current research revealed that this tendency is reversed when people face an important cue to mating-related risk: skew in the operational sex ratio, or the ratio of men to women in the local environment. Counter to the typical strategy of choice diversification, findings from four studies demonstrated that the presence of romantically unfavorable sex ratios (those featuring more same-sex than opposite-sex individuals) led heterosexual people to diversify financial resources less and instead concentrate investment in high-risk/high-return options when making lottery, stock-pool, retirement-account, and research-funding decisions. These studies shed light on a key process by which people manage risks to mating success implied by unfavorable interpersonal environments. These choice patterns have important implications for mating behavior as well as other everyday forms of decision making. © The Author(s) 2016.

Association of secondary sex ratio with smoking and parity.

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Beratis, Nicholas G; Asimacopoulou, Aspasia; Varvarigou, Anastasia

2008-03-01

To assess the sex ratio in offspring of smoking and nonsmoking mothers in relationship to parity. Prospective study. University hospital. The authors studied 2,108 term singleton neonates born between 1993 and 2002, 665 from smoking mothers and 1,443 from nonsmoking mothers. A prospective recording of maternal age, parity and smoking status, and gender of neonates delivered over a 10-year period. Secondary sex ratio in regard to maternal smoking and parity. The offspring sex ratio in the total sample studied was 1.09; in the offspring of smoking and nonsmoking mothers, it was 1.26 and 1.03, respectively, a statistically significant difference. In the offspring of smoking women who had parity 1, 2, and >or=3, it was 1.47, 1.35, and 0.92, whereas in those of nonsmoking women, it was 1.04, 1.00, and 1.03, respectively (the differences of the parity 1 and 2 groups between the offspring of smoking and nonsmoking mothers were statistically significant). Logistic regression analysis showed that the possibility of a boy being delivered by a mother who smoked was significantly greater in primiparous women than in women who had parity >or=3, independent of the maternal age. Conversely, parity did not affect significantly the sex ratio in the offspring of nonsmoking women. The findings suggest that among women who smoked, significantly more male than female offspring are born from primiparous women, whereas women who had parity >or=3 gave birth to more female offspring; biparous women give birth to significantly more male offspring, but the offspring sex ratio declined with the number of cigarettes when the mothers smoked >or=10 cigarettes per day.

The effect of climate fluctuation on chimpanzee birth sex ratio.

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Hjalmar S Kühl

Full Text Available Climate and weather conditions, such as the North Atlantic Oscillation, precipitation and temperature influence the birth sex ratio (BSR of various higher latitude species, including deer, elephant seals or northern human populations. Although, tropical regions show only little variation in temperature, climate and weather conditions can fluctuate with consequences for phenology and food resource availability. Here, we evaluate, whether the BSR of chimpanzees, inhabiting African tropical forests, is affected by climate fluctuations as well. Additionally, we evaluate, if variation in consumption of a key food resource with high nutritional value, Coula edulis nuts, is linked to both climate fluctuations and variation in BSR. We use long-term data from two study groups located in Taï National Park, Côte d'Ivoire to assess the influence of local weather conditions and the global climate driver El Niño Southern Oscillation (ENSO on offspring sex. Côte d'Ivoire has experienced considerable climate variation over the last decades, with increasing temperature and declining precipitation. For both groups we find very similar time windows around the month of conception, in which offspring sex is well predicted by ENSO, with more males following low ENSO values, corresponding to periods of high rainfall. Furthermore, we find that the time spent cracking and feeding on Coula nuts is strongly influenced by climate conditions. Although, some of our analysis suggest that a higher proportion of males is born after periods with higher nut consumption frequency, we cannot conclude decisively at this point that nut consumption may influence shifts in BSR. All results combined suggest that also chimpanzees may experience climate related shifts in offspring sex ratios as response to climate fluctuation.

The impact of sex ratio and economic status on local birth rates

OpenAIRE

Chipman, A.; Morrison, E.

2013-01-01

Human mating and reproductive behaviour can vary depending on various mechanisms, including the local sex ratio. Previous research shows that as sex ratios become female-biased, women from economically deprived areas are less likely to delay reproductive opportunities to wait for a high-investing mate but instead begin their reproductive careers sooner. Here, we show that the local sex ratio also has an impact on female fertility schedules. At young ages, a female-biased ratio is associated w...

Adult sex ratios and their implications for cooperative breeding in birds.

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Komdeur, Jan; Székely, Tamás; Long, Xiaoyan; Kingma, Sjouke A

2017-09-19

Cooperative breeding is a form of breeding system where in addition to a core breeding pair, one or more usually non-breeding individuals provide offspring care. Cooperative breeding is widespread in birds, but its origin and maintenance in contemporary populations are debated. Although deviations in adult sex ratio (ASR, the proportion of males in the adult population) have been hypothesized to influence the occurrence of cooperative breeding because of the resulting surplus of one sex and limited availability of breeding partners, this hypothesis has not been tested across a wide range of taxa. By using data from 188 bird species and phylogenetically controlled analyses, we show that cooperatively breeding species have more male-biased ASRs than non-cooperative species. Importantly, ASR predicts helper sex ratio: in species with more male-biased ASR, helper sex ratio is also more male biased. We also show that offspring sex ratios do not predict ASRs, so that the skewed ASRs emerge during the period when individuals aim to obtain a breeding position or later during adulthood. In line with this result, we found that ASR (among both cooperatively and non-cooperatively breeding species) is inversely related to sex bias in dispersal distance, suggesting that the cost of dispersal is more severe for the further-dispersing sex. As females usually disperse further in birds, this explains the generally male-biased ASR, and in combination with benefits of philopatry for males, this probably explains why ASR is more biased in cooperatively breeding species. Taken together, our results suggest that a sex bias in helping in cooperatively breeding species relates to biased ASRs. We propose that this relationship is driven by sex-specific costs and benefits of dispersal and helping, as well as other demographic factors. Future phylogenetic comparative and experimental work is needed to establish how this relationship emerges.This article is part of the themed issue 'Adult sex

India's Distorted Sex Ratio: Dire Consequences for Girls.

Science.gov (United States)

Roberts, Lisa R; Montgomery, Susanne B

2016-01-01

Female gender discrimination related to cultural preference for males is a common global problem, especially in Asian countries. Numerous laws intended to prevent discrimination on the basis of gender have been passed in India, yet the distorted female-to-male sex ratio seems to show worsening tendencies. Using detailed, two-year longitudinal chart abstraction data about delivery records of a private mission hospital in rural India, we explored if hospital birth ratio data differed in comparison to regional data, and what demographic and contextual variables may have influenced these outcomes. Using quantitative chart abstraction and qualitative contextual data, study results showed the female-to-male ratio was lower than the reported state ratio at birth. In the context of India's patriarchal structure, with its strong son preference, women are under tremendous pressure or coerced to access community-based, sex-selective identification and female fetus abortion. Nurses may be key to turning the tide.

Sex Ratio Bias Leads to the Evolution of Sex Role Reversal in Honey Locust Beetles.

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Fritzsche, Karoline; Booksmythe, Isobel; Arnqvist, Göran

2016-09-26

The reversal of conventional sex roles was enigmatic to Darwin, who suggested that it may evolve when sex ratios are female biased [1]. Here we present direct evidence confirming Darwin's hypothesis. We investigated mating system evolution in a sex-role-reversed beetle (Megabruchidius dorsalis) using experimental evolution under manipulated sex ratios and food regimes. In female-biased populations, where reproductive competition among females was intensified, females evolved to be more attractive and the sex roles became more reversed. Interestingly, female-specific mating behavior evolved more rapidly than male-specific mating behavior. We show that sexual selection due to reproductive competition can be strong in females and can target much the same traits as in males of species with conventional mating systems. Our study highlights two central points: the role of ecology in directing sexual selection and the role that females play in mating system evolution. Copyright © 2016 Elsevier Ltd. All rights reserved.

Invited Commentary: Natural Versus Unnatural Sex Ratios—A Quandary of Modern Times

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Wilcox, Allen J.; Baird, Donna D.

2011-01-01

The typical dilemma with sex-ratio findings is that when they are real, they aren’t interesting, and when they are interesting, they aren’t real. In this issue of the Journal, Fernández et al. (Am J Epidemiol. 2011;174(12):1327–1331) describe a deviation of the sex ratio that is apparently both large and real. There was a temporary but distinct spike in the proportion of boys born in Cuba around the time of the collapse of the national economy during the 1990s. Although an excess of boys does not fit the prevailing biologic theory regarding maternal stress and the sex ratio, the data are consistent with results from the Dutch famine (where population-level deprivation was even more extreme). A new quandary arises in the modern era with interpretation of the sex ratio: If the decision to abort a pregnancy is influenced by the sex of the fetus, a change in the behavior of even a small proportion of women could influence the sex ratio at birth. The possible role of sex selection in the Cuban context is discussed. PMID:22038103

Persistent sex-by-environment effects on offspring fitness and sex-ratio adjustment in a wild bird population.

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Bowers, E Keith; Thompson, Charles F; Sakaluk, Scott K

2015-03-01

A major component of sex-allocation theory, the Trivers-Willard model (TWM), posits that sons and daughters are differentially affected by variation in the rearing environment. In many species, the amount of parental care received is expected to have differing effects on the fitness of males and females. When this occurs, the TWM predicts that selection should favour adjustment of the offspring sex ratio in relation to the expected fitness return from offspring. However, evidence for sex-by-environment effects is mixed, and little is known about the adaptive significance of producing either sex. Here, we test whether offspring sex ratios vary according to predictions of the TWM in the house wren (Troglodytes aedon, Vieillot). We also test the assumption of a sex-by-environment effect on offspring using two experiments, one in which we manipulated age differences among nestlings within broods, and another in which we held nestling age constant but manipulated brood size. As predicted, females with high investment ability overproduced sons relative to those with lower ability. Males were also overproduced early within breeding seasons. In our experiments, the body mass of sons was more strongly affected by the sibling-competitive environment and resource availability than that of daughters: males grew heavier than females when reared in good conditions but were lighter than females when in poor conditions. Parents rearing broods with 1:1 sex ratios were more productive than parents rearing broods biased more strongly towards sons or daughters, suggesting that selection favours the production of mixed-sex broods. However, differences in the condition of offspring as neonates persisted to adulthood, and their reproductive success as adults varied with the body mass of sons, but not daughters, prior to independence from parental care. Thus, selection should favour slight but predictable variations in the sex ratio in relation to the quality of offspring that parents are

The financial consequences of too many men: sex ratio effects on saving, borrowing, and spending.

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Griskevicius, Vladas; Tybur, Joshua M; Ackerman, Joshua M; Delton, Andrew W; Robertson, Theresa E; White, Andrew E

2012-01-01

The ratio of males to females in a population is an important factor in determining behavior in animals. We propose that sex ratio also has pervasive effects in humans, such as by influencing economic decisions. Using both historical data and experiments, we examined how sex ratio influences saving, borrowing, and spending in the United States. Findings show that male-biased sex ratios (an abundance of men) lead men to discount the future and desire immediate rewards. Male-biased sex ratios decreased men's desire to save for the future and increased their willingness to incur debt for immediate expenditures. Sex ratio appears to influence behavior by increasing the intensity of same-sex competition for mates. Accordingly, a scarcity of women led people to expect men to spend more money during courtship, such as by paying more for engagement rings. These findings demonstrate experimentally that sex ratio influences human decision making in ways consistent with evolutionary biological theory. Implications for sex ratio effects across cultures are discussed.

Paternal effects on the human sex ratio at birth: evidence from interracial crosses.

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Khoury, M J; Erickson, J D; James, L M

1984-01-01

The effects of interracial crossing on the human sex ratio at birth were investigated using United States birth-certificate data for 1972-1979. The sex ratio was 1.059 for approximately 14 million singleton infants born to white couples, 1.033 for 2 million born to black couples, and 1.024 for 64,000 born to American Indian couples. Paternal and maternal race influences on the observed racial differences in sex ratio were analyzed using additional data on approximately 97,000 singleton infants born to white-black couples and 60,000 born to white-Indian couples. After adjustment for mother's race, white fathers had significantly more male offspring than did black fathers (ratio of sex ratios [RSR] = 1.027) and Indian fathers (RSR = 1.022). On the other hand, after adjustment for father's race, white mothers did not have more male offspring than did black mothers (RSR = 0.998) or Indian mothers (RSR = 1.009). The paternal-race effect persisted after adjustment for parental ages, education, birth order, and maternal marital status. The study shows that the observed racial differences in the sex ratio at birth are due to the effects of father's race and not the mother's. The study points to paternal determinants of the human sex ratio at fertilization and/or of the prenatal differential sex survival. PMID:6496474

Territory Quality and Plumage Morph Predict Offspring Sex Ratio Variation in a Raptor.

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Nayden Chakarov

Full Text Available Parents may adapt their offspring sex ratio in response to their own phenotype and environmental conditions. The most significant causes for adaptive sex-ratio variation might express themselves as different distributions of fitness components between sexes along a given variable. Several causes for differential sex allocation in raptors with reversed sexual size dimorphism have been suggested. We search for correlates of fledgling sex in an extensive dataset on common buzzards Buteo buteo, a long-lived bird of prey. Larger female offspring could be more resource-demanding and starvation-prone and thus the costly sex. Prominent factors such as brood size and laying date did not predict nestling sex. Nonetheless, lifetime sex ratio (LSR, potentially indicative of individual sex allocation constraints and overall nestling sex were explained by territory quality with more females being produced in better territories. Additionally, parental plumage morphs and the interaction of morph and prey abundance tended to explain LSR and nestling sex, indicating local adaptation of sex allocation However, in a limited census of nestling mortality, not females but males tended to die more frequently in prey-rich years. Also, although females could have potentially longer reproductive careers, a subset of our data encompassing full individual life histories showed that longevity and lifetime reproductive success were similarly distributed between the sexes. Thus, a basis for adaptive sex allocation in this population remains elusive. Overall, in common buzzards most major determinants of reproductive success appeared to have no effect on sex ratio but sex allocation may be adapted to local conditions in morph-specific patterns.

Live birth sex ratios and father’s geographic origins in Jerusalem, 1964–1976

Science.gov (United States)

Groeger, J; Opler, M; Kleinhaus, K; Perrin, MC; Calderon-Margalit, R; Manor, O; Paltiel, O; Conley, D; Harlap, S; Malaspina, D

2016-01-01

Objective To examine whether ancestry influenced sex ratios of offspring in a birth cohort before parental antenatal sex selection influenced offspring sex. Methods We measured the sex ratio as the percent of males according to countries of birth of paternal and maternal grandfathers in 91,459 live births from 1964 to 1976 in the Jerusalem Perinatal Study. Confidence limits (CI) were computed based on an expected sex ratio of 1.05, which is 51.4% male. Results Of all live births recorded, 51.4% were male. Relative to Jewish ancestry (51.4% males), significantly more males (1,761) were born to Muslim ancestry (54.5, 95% CI=52.1–56.8, p=.01). Among the former, sex ratios were not significantly associated with paternal or maternal age, education, or offspring’s birth order. Consistent with a preference for male offspring, the sex ratio decreased despite increasing numbers of births over the 13-year period. Sex ratios were not affected by maternal or paternal origins in North Africa or Europe. However, the offspring whose paternal grandfathers were born in Western Asia included fewer males than expected (50.7, 50.1–51.3, p=.02), whether the father was born abroad (50.7) or in Israel (50.8). This was observed for descendents of paternal grandfathers born in Lebanon (47.6), Turkey (49.9), Yemen & Aden (50.2), Iraq (50.5), Afghanistan (50.5), Syria (50.6), and Cyprus (50.7); but not for those from India (51.5) or Iran (51.9). The West Asian group showed the strongest decline in sex ratios with increasing paternal family size. Conclusions A decreased sex ratio associated with ancestry in Western Asia is consistent with reduced ability to bear sons by a subset of Jewish men in the Jerusalem cohort. Lower sex ratios may be due to pregnancy stress, which may be higher in this subgroup. Alternatively, a degrading Y chromosome haplogroup or other genetic or epigenetic differences on male germ lines could affect birth ratios, such as differential exposure to an

The male handicap: male-biased mortality explains skewed sex ratios in brown trout embryos.

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Morán, P; Labbé, L; Garcia de Leaniz, C

2016-12-01

Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire × dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates. © 2016 The Authors.

Different sex ratios of children born to Indian and Pakistani immigrants in Norway

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Brekke Torkel

2010-08-01

Full Text Available Abstract Background A low female-to-male ratio has been observed in different Asian countries, but this phenomenon has not been well studied among immigrants living in Western societies. In this study, we investigated whether a low female-to-male ratio exists among Indian and Pakistani immigrants living in Norway. In particular, we investigated whether the determination of sex via ultrasound examination, a common obstetric procedure that has been used in Norway since the early 1980 s, has influenced the female-to-male ratio among children born to parents of Indian or Pakistani origin. Methods We performed a retrospective cohort study of live births in mothers of Indian (n = 1597 and Pakistani (n = 5617 origin. Data were obtained from "Statistics Norway" and the female-to-male (F/M sex ratio was evaluated among 21,325 children born, in increasing birth order, during three stratified periods (i.e., 1969-1986, 1987-1996, and 1997-2005. Results A significant low female-to-male sex ratio was observed among children in the third and fourth birth order (sex ratio 65; 95% CI 51-80 from mothers of Indian origin who gave birth after 1987. Sex ratios did not deviate from the expected natural variation in the Indian cohort from 1969 to 1986, and remained stable in the Pakistani cohort during the entire study period. However, the female-to-male sex ratio seemed less skewed in recent years (i.e., 1997-2005. Conclusion Significant differences were observed in the sex ratio of children born to mothers of Indian origin compared with children born to mothers of Pakistani origin. A skewed number of female births among higher birth orders (i.e., third or later may partly reflect an increase in sex-selective abortion among mothers of Indian origin, although the numbers are too small to draw firm conclusions. Further research is needed to explain the observed differences in the female-to-male ratio among members of these ethnic groups who reside in Norway.

Manipulation of primary sex ratio in birds: lessons from the homing pigeon (Columba livia domestica).

Science.gov (United States)

Goerlich-Jansson, Vivian C; Müller, Martina S; Groothuis, Ton G G

2013-12-01

Across various animal taxa not only the secondary sex ratio but also the primary sex ratio (at conception) shows significant deviations from the expected equal proportions of sons and daughters. Birds are especially intriguing to study this phenomenon as avian females are the heterogametic sex (ZW); therefore sex determination might be under direct control of the mother. Avian sex ratios vary in relation to environmental or maternal condition, which can also affect the production of maternal steroids that in turn are involved in reproduction and accumulate in the developing follicle before meiosis. As the proximate mechanisms underlying biased primary sex ratio are largely elusive, we explored how, and to what extent, maternal steroid hormones may be involved in affecting primary or secondary sex ratio in clutches of various species of pigeons. First we demonstrated a clear case of seasonal change in sex ratio in first eggs both in the Rock Pigeon (Columba livia) and in a related species, the Wood Pigeon (Columba palumbus), both producing clutches of two eggs. In the Homing Pigeon (Columba livia domestica), domesticated from the Rock Pigeon, testosterone treatment of breeding females induced a clear male bias, while corticosterone induced a female bias in first eggs and we argue that this is in line with sex allocation theory. We next analyzed treatment effects on follicle formation, yolk mass, and yolk hormones, the latter both pre- and post-ovulatory, in order to test a diversity of potential mechanisms related to both primary and secondary sex ratio manipulation. We conclude that maternal plasma hormone levels may affect several pre-ovulatory mechanisms affecting primary sex ratio, whereas egg hormones are probably involved in secondary sex ratio manipulation only.

Mother's prior intrauterine position affects the sex ratio of her offspring in house mice.

Science.gov (United States)

Vandenbergh, J G; Huggett, C L

1994-11-08

Sex ratio alterations related to environmental factors occur in several mammals, but no mechanism has been identified to explain the adjustment. Intrauterine position (IUP) may provide the context in which such alterations occur. Previous studies on house mice and gerbils reveal that the position of a fetus in the uterus in relation to the sex of its neighbors influences its later anatomy, physiology, and behavior. The anogenital distance (AGD) of females located between two males (2M) is longer than that of females not between two males (OM). We have found that the IUP, as determined by cesarean section and by an index of the AGD, correlates with the sex ratio of the litters produced by female mice. The sex ratio of the first litter born to 2M females was 58% males, for 1M females was 51% males and for OM females was 42% males. The effect on sex ratio continues into the second litter. The number of pups produced by mothers of different IUPs in her first two litters did not differ, suggesting that the sex ratio adjustment occurs prior to parturition. These results provide a basis for the natural variability observed in sex ratios of litter-bearing mammals and suggest that one or more intrauterine mechanisms may be responsible for environmentally related sex ratio alterations.

Does predation control adult sex ratios and longevities in marine pelagic copepods?

DEFF Research Database (Denmark)

Hirst, A.G.; Bonnet, D.; Conway, D.V.P.

2010-01-01

We assess the causes of adult sex ratio skew in marine pelagic copepods by examining changes in these ratios between the juveniles and adults, sexual differences in juvenile stage durations, and mortality rates of adults in the field and laboratory (when free from predators). In the field, late...... copepodite stages (CIV and CV) commonly have sex ratios that are either not significantly different from equity (1 : 1), or slightly male biased. By contrast, in adults, these ratios are commonly significantly biased toward female dominance. Sex ratio skews are therefore primarily attributable to processes...... in adults. Members of the non-Diaptomoidea have especially skewed adult ratios; in the members Oithonidae and Clausocalanidae this is not generated from differences between male and female adult physiological longevity (i.e., laboratory longevity when free of predators). In the genera Acartia, Oithona...

National, regional, and global sex ratios of infant, child, and under-5 mortality and identification of countries with outlying ratios: a systematic assessment

OpenAIRE

Alkema, Leontine; Chao, Fengqing; You, Danzhen; Pedersen, Jon; Sawyer, Cheryl C

2014-01-01

Background: Under natural circumstances, the sex ratio of male to female mortality up to the age of 5 years is greater than one but sex discrimination can change sex ratios. The estimation of mortality by sex and identification of countries with outlying levels is challenging because of issues with data availability and quality, and because sex ratios might vary naturally based on differences in mortality levels and associated cause of death distributions. Methods: For this systematic anal...

Seasonal Sex Ratio Trend in the European Kestrel : An Evolutionarily Stable Strategy Analysis

NARCIS (Netherlands)

Pen, I.R.; Weissing, F.J.; Daan, S.

We present an evolutionarily stable strategy (ESS) model to analyze selection on seasonal variation in the brood sex ratio, as observed in several species of raptorial birds. The model is specifically tailored to the life history of the European kestrel, and it reflects the maturation time

Gender Inequality and the Sex Ratio in Three Emerging Economies

OpenAIRE

Prabir C. Bhattacharya

2012-01-01

The aim of this paper is to study inequality and deprivations as reflected in the human sex ratio (commonly defined as the number of males per 100 females). The particular focus is on three emerging economies, viz., Russia, India and China. The paper compares and contrasts the experiences of these countries and discusses policy issues. It is noted that while the feminist perspective on the issues surrounding the sex ratio is important, it would be wrong to view these issues always or exclusiv...

India’s Distorted Sex Ratio: Dire Consequences for Girls

Science.gov (United States)

Roberts, Lisa R.; Montgomery, Susanne B.

2017-01-01

Female gender discrimination related to cultural preference for males is a common global problem, especially in Asian countries. Numerous laws intended to prevent discrimination on the basis of gender have been passed in India, yet the distorted female-to-male sex ratio seems to show worsening tendencies. Using detailed, two-year longitudinal chart abstraction data about delivery records of a private mission hospital in rural India, we explored if hospital birth ratio data differed in comparison to regional data, and what demographic and contextual variables may have influenced these outcomes. Using quantitative chart abstraction and qualitative contextual data, study results showed the female-to-male ratio was lower than the reported state ratio at birth. In the context of India’s patriarchal structure, with its strong son preference, women are under tremendous pressure or coerced to access community-based, sex-selective identification and female fetus abortion. Nurses may be key to turning the tide. PMID:28286369

The effects of sex-ratio and density on locomotor activity in the house fly, Musca domestica

DEFF Research Database (Denmark)

Bahrndorff, Simon; Kjaersgaard, Anders; Pertoldi, Cino

2012-01-01

Although locomotor activity is involved in almost all behavioral traits, there is a lack of knowledge on what factors affect it. This study examined the effects of sex-ratio and density on the circadian rhythm of locomotor activity of adult Musca domestica L. (Diptera: Muscidae) using an infra......-red light system. Sex-ratio significantly affected locomotor activity, increasing with the percentage of males in the vials. In accordance with other studies, males were more active than females, but the circadian rhythm of the two sexes was not constant over time and changed during the light period...... of the behavioral interactions between houseflies and highlight the importance of these factors when designing behavioral experiments using M. domestica....

Female-biased sex ratios in marine pelagic copepods: Comment on Gusmao et al. (2013)

DEFF Research Database (Denmark)

Hirst, Andrew G.; Bonnet, D; Conway, DVP

2013-01-01

Gusmao et al. (2013; Mar Ecol Prog Ser 482:279-298) review causes of sex ratio skew in pelagic copepods and in doing so repeatedly dispute the paper of Hirst et al. (2010) ‘Does predation control adult sex ratios and longevities in marine pelagic copepods?’ Here we respond to some important error...... in their citation of our paper and briefly highlight where future work is needed in order to attribute the causes of strong sex ratio skew seen in some copepod families......Gusmao et al. (2013; Mar Ecol Prog Ser 482:279-298) review causes of sex ratio skew in pelagic copepods and in doing so repeatedly dispute the paper of Hirst et al. (2010) ‘Does predation control adult sex ratios and longevities in marine pelagic copepods?’ Here we respond to some important errors...

Increased sex ratio in Russia and Cuba after Chernobyl: a radiological hypothesis.

Science.gov (United States)

Scherb, Hagen; Kusmierz, Ralf; Voigt, Kristina

2013-08-15

The ratio of male to female offspring at birth may be a simple and non-invasive way to monitor the reproductive health of a population. Except in societies where selective abortion skews the sex ratio, approximately 105 boys are born for every 100 girls. Generally, the human sex ratio at birth is remarkably constant in large populations. After the Chernobyl nuclear power plant accident in April 1986, a long lasting significant elevation in the sex ratio has been found in Russia, i.e. more boys or fewer girls compared to expectation were born. Recently, also for Cuba an escalated sex ratio from 1987 onward has been documented and discussed in the scientific literature. By the end of the eighties of the last century in Cuba as much as about 60% of the food imports were provided by the former Soviet Union. Due to its difficult economic situation, Cuba had neither the necessary insight nor the political strength to circumvent the detrimental genetic effects of imported radioactively contaminated foodstuffs after Chernobyl. We propose that the long term stable sex ratio increase in Cuba is essentially due to ionizing radiation. A synoptic trend analysis of Russian and Cuban annual sex ratios discloses upward jumps in 1987. The estimated jump height from 1986 to 1987 in Russia measures 0.51% with a 95% confidence interval (0.28, 0.75), p value Cuba the estimated jump height measures 2.99% (2.39, 3.60), p value Cuba and by radiological analyses of remains in Cuba for Cs-137 and Sr-90. If the evidence for the hypothesis is strengthened, there is potential to learn about genetic radiation risks and to prevent similar effects in present and future exposure situations.

Pre-ovulation control of hatchling sex ratio in the Seychelles warbler

NARCIS (Netherlands)

Komdeur, J; Magrath, MJL; Krackow, S

2002-01-01

Females of some bird species have a high degree of control over the sex ratio of their offspring at laying. Although several mechanisms have been put forward to explain how females might control the sex of their eggs, virtually nothing is known. As females are the heterogametic sex in birds,

Offspring sex ratio is related to paternal train elaboration and yolk corticosterone in peafowl.

Science.gov (United States)

Pike, Thomas W; Petrie, Marion

2005-06-22

Several recent experimental studies have provided strong evidence for the ability of birds to manipulate the sex ratio of their offspring prior to laying. Using a captive population of peafowl (Pavo cristatus), we tested experimentally the effects of paternal attractiveness on offspring sex ratio, and related sex ratio deviations to egg-yolk concentrations of testosterone, 17beta-estradiol and corticosterone. When females were mated to males whose attractiveness had been experimentally reduced by removing prominent eyespot feathers from their trains, they produced significantly more female offspring, had significantly higher yolk corticosterone concentrations and tended to have lower levels of yolk testosterone than when mated to the same males with their full complement of feathers. Concentrations of 17beta-estradiol did not vary consistently with sex ratio biases. These findings add to the small number of studies providing experimental evidence that female birds can control the primary sex ratio of their offspring in response to paternal attractiveness, and highlight the possibility that corticosterone and perhaps testosterone are involved in the sex manipulation process in birds.

The impact of sex ratio and economic status on local birth rates.

Science.gov (United States)

Chipman, A; Morrison, E

2013-04-23

Human mating and reproductive behaviour can vary depending on various mechanisms, including the local sex ratio. Previous research shows that as sex ratios become female-biased, women from economically deprived areas are less likely to delay reproductive opportunities to wait for a high-investing mate but instead begin their reproductive careers sooner. Here, we show that the local sex ratio also has an impact on female fertility schedules. At young ages, a female-biased ratio is associated with higher birth rates in the poorest areas, whereas the opposite is true for the richest areas. At older ages, a female-biased ratio is associated with higher birth rates in the richest, but not the poorest areas. These patterns suggest that female-female competition encourages poorer women to adopt a fast life-history strategy and give birth early, and richer women to adopt a slow life-history strategy and delay reproduction.

An unstable social environment affects sex ratio in guinea pigs : an adaptive maternal effect?

NARCIS (Netherlands)

Kemme, Kristina; Kaiser, Sylvia; von Engelhardt, Nikolaus; Wewers, Dirk; Groothuis, Ton; Sachser, Norbert

2009-01-01

Evolutionary theory suggests that offspring sex should be adjusted to environmental conditions in order to maximize future reproductive success. In several animal taxa environmental factors indeed affect the secondary sex ratio. In humans, changes in the sex ratio at birth have been associated with

Sex ratio distribution and fecundity of the claroteid catfish Clarotes ...

African Journals Online (AJOL)

Sex ratio distribution and fecundity of Clarotes laticeps were investigated between January 2010 and December 2012 in the lower River Niger. Samples were collected every two weeks for 36 months from six sampling sites, using a combination of baited longlines, gill nets and cast nets. Sexes of captured specimens were ...

Socioeconomic status influences sex ratios in a Chinese rural population.

Science.gov (United States)

Luo, Liqun; Ding, Rui; Gao, Xiali; Sun, Jingjing; Zhao, Wei

2017-01-01

According to the logic of the Trivers-Willard hypothesis, in a human population, if socioeconomic status is transmitted across generations to some extent, and if sons of high-status parents tend to have higher reproductive success than daughters, while daughters of low-status parents tend to have higher reproductive success than sons, then we should expect that offspring sex ratio is positively associated with socioeconomic status. This study examines whether the assumptions and prediction of this hypothesis apply to a rural population in northern China. Results show that (1) current family socioeconomic status is positively related to family head's father's socioeconomic status in around 1950, (2) low-status family heads have more grandchildren through their daughters than their sons, whereas high- or middle-status family heads have more grandchildren through sons, and (3) as family heads' status increases, they tend to produce a higher offspring sex ratio. Therefore, the assumptions and prediction of the hypothesis are met in the study population. These results are discussed in reference to past studies on sex ratio manipulation among humans.

Strong but variable associations between social dominance and clutch sex ratio in a colonial corvid

NARCIS (Netherlands)

Salomons, H. M.; Dijkstra, C.; Verhulst, S.

2008-01-01

We studied primary sex ratio of clutches in relation to social dominance for 6 years in a colony of free-living jackdaws, a small corvid. Social dominance was strongly associated with clutch sex ratio, with the difference in clutch sex ratio between the most and least dominant pairs being 30-40%. To

Phenotypic sex ratios of Atriplex canescens shrubs in relation to cattle browsing

Science.gov (United States)

Andres F. Cibils; David M. Swift; Richard H. Hart

2001-01-01

Previous studies conducted at our research site on the shortgrass steppe in Colorado showed that phenotypic sex ratios of tetraploid fourwing saltbush (Atriplex canescens Pursh [Nutt]) shrubs were less female biased in grazed pastures than in adjacent exclosures. The potential effects of cattle browsing on shrub sex ratios were studied both in the field and in a...

Skewed Marriage Markets and Sex Ratios of Finnish People in their Twenties

Directory of Open Access Journals (Sweden)

Lassi Lainiala

2014-03-01

Full Text Available This article studies variation in regional sex ratios in Finland and outlines potential implications of the skewed sex ratios for family formation patterns. Difficulties in finding a suitable partner are typically mentioned as one of the most important reasons for remaining childless, and we explore if this reason is apparent structurally at the regional macro level. We found significant variation in sex ratios in age-groups 18–30 at the regional and sub-regional levels. Of the whole 20–29-year old population in Finland, almost 50 percent live in sub-region areas with a male surplus. As expected, a higher proportion of men compared to women appears to increase fertility of women in younger age groups. Contrary to expectations, high male-female ratios were not related to higher proportion of women living with a partner

Increased sex ratio in Russia and Cuba after Chernobyl: a radiological hypothesis

Science.gov (United States)

2013-01-01

Background The ratio of male to female offspring at birth may be a simple and non-invasive way to monitor the reproductive health of a population. Except in societies where selective abortion skews the sex ratio, approximately 105 boys are born for every 100 girls. Generally, the human sex ratio at birth is remarkably constant in large populations. After the Chernobyl nuclear power plant accident in April 1986, a long lasting significant elevation in the sex ratio has been found in Russia, i.e. more boys or fewer girls compared to expectation were born. Recently, also for Cuba an escalated sex ratio from 1987 onward has been documented and discussed in the scientific literature. Presentation of the hypothesis By the end of the eighties of the last century in Cuba as much as about 60% of the food imports were provided by the former Soviet Union. Due to its difficult economic situation, Cuba had neither the necessary insight nor the political strength to circumvent the detrimental genetic effects of imported radioactively contaminated foodstuffs after Chernobyl. We propose that the long term stable sex ratio increase in Cuba is essentially due to ionizing radiation. Testing of the hypothesis A synoptic trend analysis of Russian and Cuban annual sex ratios discloses upward jumps in 1987. The estimated jump height from 1986 to 1987 in Russia measures 0.51% with a 95% confidence interval (0.28, 0.75), p value < 0.0001. In Cuba the estimated jump height measures 2.99% (2.39, 3.60), p value < 0.0001. The hypothesis may be tested by reconstruction of imports from the world markets to Cuba and by radiological analyses of remains in Cuba for Cs-137 and Sr-90. Implications of the hypothesis If the evidence for the hypothesis is strengthened, there is potential to learn about genetic radiation risks and to prevent similar effects in present and future exposure situations. PMID:23947741

Do brood sex ratio, nestling development and sex affect fledging timing and order? An experimental study on great tits

NARCIS (Netherlands)

Radersma, Reinder; Tinbergen, Joost M.; Komdeur, Jan

The process of nest leaving (fledging) in hole-breeding passerines is largely unexplored, although it is potentially an important facet of reproduction. We used the great tit, Parus major, to investigate whether fledging timing and order were affected by nestling development and sex, as well as the

Transgenerational plasticity mitigates the impact of global warming to offspring sex ratios.

Science.gov (United States)

Donelson, Jennifer M; Munday, Philip L

2015-08-01

Global warming poses a threat to organisms with temperature-dependent sex determination because it can affect operational sex ratios. Using a multigenerational experiment with a marine fish, we provide the first evidence that parents developing from early life at elevated temperatures can adjust their offspring gender through nongenetic and nonbehavioural means. However, this adjustment was not possible when parents reproduced, but did not develop, at elevated temperatures. Complete restoration of the offspring sex ratio occurred when parents developed at 1.5 °C above the present-day average temperature for one generation. However, only partial improvement in the sex ratio occurred at 3.0 °C above average conditions, even after two generations, suggesting a limitation to transgenerational plasticity when developmental temperature is substantially increased. This study highlights the potential for transgenerational plasticity to ameliorate some impacts of climate change and that development from early life may be essential for expression of transgenerational plasticity in some traits. © 2015 John Wiley & Sons Ltd.

The potential pitfalls of studying adult sex ratios at aggregate levels in humans

NARCIS (Netherlands)

Pollet, Thomas V.; Stoevenbelt, Andrea H.; Kuppens, Toon

2017-01-01

Human adult sex ratios have been studied extensively across the biological and social sciences. While several studies have examined adult sex ratio effects in a multilevel perspective, many studies have focused on effects at an aggregated level only. In this paper, we review some key issues relating

The sex ratio of offspring is associated with the mothers' age at menarche

DEFF Research Database (Denmark)

Fukuda, Misao; Fukuda, Kiyomi; Shimizu, Takashi

2011-01-01

BACKGROUND Early menarcheal age is a risk factor for breast and ovarian cancers and is also associated with an increased spontaneous abortion rate. The aim of this study was to investigate whether there is a link between early menarcheal age and the offspring sex ratio. METHODS We recorded the sex...... of 21208 live born infants, all singletons, born to 10 847 premenopausal women (mean attending age: 37.5 ± 7.2 years, range 22-54) who attended our clinics for obstetrical and gynaecological assessment. We calculated the sex ratio of newborn infants in relation to the mothers' age of menarche (from 9 to 18...... years) and to the number of infants per woman (i.e. fertility index). RESULTS A low offspring sex ratio (males/females) of 0.800 was observed in mothers who entered menarche at the age of 9 years; the odds ratio (OR) (95% confidence intervals) compared with those of control group with menarche at age 14...

Flock sizes and sex ratios of canvasbacks in Chesapeake Bay and North Carolina

Science.gov (United States)

Haramis, G.M.; Derleth, E.L.; Link, W.A.

1994-01-01

Knowledge of the distribution, size, and sex ratios of flocks of wintering canvasbacks (Aythya valisineria) is fundamental to understanding the species' winter ecology and providing guidelines for management. Consequently, in winter 1986-87, we conducted 4 monthly aerial photographic surveys to investigate temporal changes in distribution, size, and sex ratios of canvasback flocks in traditional wintering areas of Chesapeake Bay and coastal North Carolina. Surveys yielded 35mm imagery of 194,664 canvasbacks in 842 flocks. Models revealed monthly patterns of flock size in North Carolina and Virginia, but no pattern of change in Maryland. A stepwise analysis of flock size and sex ratio fit a common positive slope (increasing proportion male) for all state-month datasets, except for North Carolina in February where the slope was larger (P lt 0.001). State and month effects on intercepts were significant (P lt 0.001) and confirmed a previously identified latitudinal gradient in sex ratio in the survey region. There was no relationship between flock purity (% canvasbacks vs. other species) and flock size except in North Carolina in January, February, and March when flock purity was related to flock size. Contrasting characteristics in North Carolina with regard to flock size (larger flocks) and flock purity suggested that proximate factors were reinforcing flocking behavior and possibly species fidelity there. Of possible factors, the need to locate foraging sites within this large, open-water environment was hypothesized to be of primary importance. Comparison of January 1981 and 1987 sex ratios indicated no change in Maryland, but lower (P lt 0.05) canvasback sex ratios (proportion male) in Virginia and North Carolina.

The sex ratio of siblings of individuals with a history of developmental language disorder

DEFF Research Database (Denmark)

Mouridsen, Svend Erik; Hauschild, Karen-Marie

2010-01-01

There is a well documented predominance of males diagnosed with neurodevelopmental disorders. The influence of sex steroids upon brain development has been suggested to mediate sex differences in developmental psychopathology, and has been epitomized in the 'extreme male brain theory......'. The objective of this study was to extend previous studies dealing with the extreme male brain theory and to study the sex ratio (proportion of males) in the siblings of 469 individuals with a developmental language disorder (DLD) who were consecutively assessed in the same clinic during a period of 10 years....... Among their 908 live-born siblings, 503 were males and 405 females. This yields a sex ratio of 0.554, which is significantly higher than the Danish live birth sex ratio of 0.514 over the same period (P = 0.02). Our findings are consistent with the hypothesis that male sex hormones may be implicated...

The mystery of missing female children in the Caucasus: an analysis of sex ratios by birth order.

Science.gov (United States)

Michael, Marc; King, Lawrence; Guo, Liang; McKee, Martin; Richardson, Erica; Stuckler, David

2013-06-01

Official data on sex ratios at birth suggest a rise in sex-selective abortions in some post-Soviet states following the introduction of ultrasonography. However, questions remain about the validity of official data in these nations as well as whether the high sex ratios at birth are a statistical artifact. Trends in sex ratios at birth from 1985 to 2009 for 12 post-Soviet states were examined using vital registration data. For the three countries that had had a Demographic and Health Survey (DHS) in 2005-2010 (Armenia, Azerbaijan and Moldova), survey data were used to calculate sex ratios at birth according to birth order, and vital registration data for 2010 were used to estimate the number of "missing" female births (if any). Official data revealed elevated sex ratios at birth in Armenia (117), Azerbaijan (116) and Georgia (121), but not in other post-Soviet states. According to DHS data, sex ratios were high in Armenia and Azerbaijan for first births (138 and 113, respectively); if the first child was a girl, the sex ratio in Armenia was even higher for the second birth (154). Overall, the number of girls born in these countries in 2010 was 10% lower than expected, consistent with 1,972 sex-selective abortions in Armenia and 8,381 in Azerbaijan. Sex ratios did not vary by birth order in Moldova. Sex-selective abortion appears to be common in Azerbaijan and Armenia. Family planning and legal interventions are needed to address this issue.

Sex ratios in juveniles and adults of Dichroplus maculipennis (Blanchard and Borellia bruneri (Rehn (Orthoptera: Acrididae

Directory of Open Access Journals (Sweden)

Yanina Mariottini

2015-06-01

Full Text Available Dichroplus maculipennis and Borellia bruneri are two of the 18 grasshopper species of actual or potential economic relevance as pests in Argentina. The objective of this study was to estimate the sex ratios for adults and older nymphs of D. maculipennis and B. bruneri in the field, and analyze possible temporal variations. The study was conducted during seven seasons (2005-06 to 2011-12 in representative plant communities of the southern Pampas region. A total of 4536 individuals of D. maculipennis, and 6038 individuals of B. bruneri were collected. The sex ratio registered in older nymphs for D. maculipennis and B. bruneri did not deviate from a 1:1 ratio (p > 0.05, suggesting that these species have such a primary sex ratio. However, a significant bias in sex composition in adults of both species was observed (p < 0.05. The sex ratio in adults of D. maculipennis was different in five of the 18 sampling dates carried out. In three sampling dates it was biased toward males, while in the other two it was biased toward females. Taking into account the sex ratio by sampling season, significant differences were recorded in two seasons. In 2007-08 the sex ratio was biased toward males (1 F:2.26 M, while in 2008-09 it was biased toward females (1.35 F:1 M. The sex ratio in adults of B. bruneri was always biased toward males (p < 0.05. We conclude that results obtained in this study indicate that various factors like differential survival, dispersion, predation, among others, could have modified the primary sex ratio in these species.

Hatchling sex ratio and female mating status in the great reed warbler, Acrocephalus arundinaceus (Aves, Passeriformes): further evidence for offspring sex ratio manipulation

Czech Academy of Sciences Publication Activity Database

Trnka, A.; Prokop, P.; Kašová, M.; Sobeková, Karolina; Kocian, Ľ.

2012-01-01

Roč. 79, č. 2 (2012), s. 212-217 ISSN 1125-0003 Institutional support: RVO:68081766 Keywords : Great reed warbler * sex ratio * social polygyny Subject RIV: EG - Zoology Impact factor: 0.890, year: 2012

A Multinomial Model of Fertility Choice and Offspring Sex-Ratios in India

OpenAIRE

Rubiana Chamarbagwala; Martin Ranger

2007-01-01

Fertility decline in developing countries may have unexpected demographic consequences. Although lower fertility improves nutrition, health, and human capital investments for surviving children, little is known about the relationship between fertility outcomes and female-male offspring sex-ratios. Particularly in countries with a cultural preference for sons, like India and China, fertility decline may deteriorate the already imbalanced sex-ratios. We use the fertility histories of over 90,00...

Manipulation of primary sex ratio in birds : Lessons from the Homing Pigeon (Columba livia domestica)

NARCIS (Netherlands)

Goerlich-Jansson, Vivian C.; Muller, Martina S.; Groothuis, Ton G. G.

2013-01-01

Across various animal taxa not only the secondary sex ratio but also the primary sex ratio (at conception) shows significant deviations from the expected equal proportions of sons and daughters. Birds are especially intriguing to study this phenomenon as avian females are the heterogametic sex (ZW);

Different male versus female breeding periodicity helps mitigate offspring sex ratio skews in sea turtles

Directory of Open Access Journals (Sweden)

Graeme Clive Hays

2014-09-01

Full Text Available The implications of climate change for global biodiversity may be profound with those species with little capacity for adaptation being thought to be particularly vulnerable to warming. A classic case of groups for concern are those animals exhibiting temperature-dependent sex-determination (TSD, such as sea turtles, where climate warming may produce single sex populations and hence extinction. We show that, globally, female biased hatchling sex ratios dominate sea turtle populations (exceeding 3:1 in >50% records, which, at-a-glance, reiterates concerns for extinction. However, we also demonstrate that more frequent breeding by males, empirically shown by satellite tracking 23 individuals and supported by a generalized bio-energetic life history model, generates more balanced operational sex ratios (OSRs. Hence, concerns of increasingly skewed hatchling sex ratios and reduced population viability are less acute than previously thought for sea turtles. In fact, in some scenarios skewed hatchling sex ratios in groups with TSD may be adaptive to ensure optimum OSRs.

Determination of sex-ratio by birth order in an urban community in Manipur.

Science.gov (United States)

Brogen, Akoijam S; Shantibala, K; Rajkumari, Bishwalata; Laishram, Jalina

2009-01-01

To determine the sex ratio by birth order and to assess the sex preference of the couples in an urban community. A cross sectional study, in an urban community in Manipur, was conducted among the currently married couples. Data on background characteristics of the couple, family pedigree chart (of the offspring) including history of abortion, stillbirth, death of child of the couple, sex preference and Pre-natal Diagnostic Techniques (Regulation and Prevention of Misuse) Act [PNDT Act] were collected through a structured interview. Data were analyzed using descriptive and chi-square statistics. There were a total of 1777 births to the 855 couples interviewed. There were 900 females per 1000 males for the 1st birth order but the sex ratio was favorable towards females in the 2nd, 3rd and 4th birth orders. Among both the husbands and wives, being more educated was significantly associated (p<0.05) with preferring lesser number of children, using new technology for sex selection and having heard of the PNDT Act. Majority of those who wanted to use new technology for sex selection (128, 56.6%) preferred to have male child. Sex ratio in this community was favorable towards females, though it was less among the first born babies.

Influence of electromagnetic pulse on the offspring sex ratio of male BALB/c mice.

Science.gov (United States)

Li, Jin-Hui; Jiang, Da-Peng; Wang, Ya-Feng; Yan, Jia-Jia; Guo, Qi-Yan; Miao, Xia; Lang, Hai-Yang; Xu, Sheng-Long; Liu, Jun-Ye; Guo, Guo-Zhen

2017-09-01

Public concern is growing about the exposure to electromagnetic fields (EMF) and its effect on male reproductive health. Detrimental effect of EMF exposure on sex hormones, reproductive performance and sex-ratio was reported. The present study was designed to clarify whether paternal exposure to electromagnetic pulse (EMP) affects offspring sex ratio in mice. 50 male BALB/c mice aged 5-6 weeks were exposed to EMP daily for 2 weeks before mated with non-exposed females at 0d, 7d, 14d, 21d and 28d after exposure. Sex hormones including total testosterone, LH, FSH, and GnRH were detected using radioimmunoassay. The sex ratio was examined by PCR and agarose gel electrophoresis. The results of D0, D21 and D28 showed significant increases compared with sham-exposed groups. The serum testosterone increased significantly in D0, D14, D21, and D28 compared with sham-exposed groups (p<0.05). Overall, this study suggested that EMP exposure may lead to the disturbance of reproductive hormone levels and affect the offspring sex ratio. Copyright © 2017. Published by Elsevier B.V.

Disestablishing Sex: The Case for Released-Time Sex Education

Science.gov (United States)

Glanzer, Perry L.

2011-01-01

Allowing nonschool organizations to provide sex education in a released-time format would disestablish state-funded sex education and give families a choice in the sex education that would be provided for their children. Released-time programs, as originally conceived and currently practiced, allow students to be released for a period of time…

Invited Commentary: Natural Versus Unnatural Sex Ratios—A Quandary of Modern Times

OpenAIRE

Wilcox, Allen J.; Baird, Donna D.

2011-01-01

The typical dilemma with sex-ratio findings is that when they are real, they aren’t interesting, and when they are interesting, they aren’t real. In this issue of the Journal, Fernández et al. (Am J Epidemiol. 2011;174(12):1327–1331) describe a deviation of the sex ratio that is apparently both large and real. There was a temporary but distinct spike in the proportion of boys born in Cuba around the time of the collapse of the national economy during the 1990s. Although an excess of boys does...

Spatio-temporal variation in the incubation duration and sex ratio of hawksbill hatchlings: implication for future management.

Science.gov (United States)

dei Marcovaldi, Maria A G; Santos, Armando J B; Santos, Alexsandro S; Soares, Luciano S; Lopez, Gustave G; Godfrey, Matthew H; López-Mendilaharsu, Milagros; Fuentes, Mariana M P B

2014-08-01

Climate change poses a unique threat to species with temperature dependent sex determination (TSD), such as marine turtles, where increases in temperature can result in extreme sex ratio biases. Knowledge of the primary sex ratio of populations with TSD is key for providing a baseline to inform management strategies and to accurately predict how future climate changes may affect turtle populations. However, there is a lack of robust data on offspring sex ratio at appropriate temporal and spatial scales to inform management decisions. To address this, we estimate the primary sex ratio of hawksbill hatchlings, Eretmochelys imbricata, from incubation duration of 5514 in situ nests from 10 nesting beaches from two regions in Brazil over the last 27 years. A strong female bias was estimated in all beaches, with 96% and 89% average female sex ratios produced in Bahia (BA) and Rio Grande do Norte (RN). Both inter-annual (BA, 88 to 99%; RN, 75 to 96% female) and inter-beach (BA, 92% to 97%; RN, 81% to 92% female) variability in mean offspring sex ratio was observed. These findings will guide management decisions in Brazil and provide further evidence of highly female-skew sex ratios in hawksbill turtles. Copyright © 2014 Elsevier Ltd. All rights reserved.

No evidence for selective follicle abortion underlying primary sex ratio adjustment in pigeons

NARCIS (Netherlands)

Goerlich, Vivian C.; Dijkstra, Cornelis; Groothuis, Antonius

Primary sex ratio adjustment in birds has been extensively studied, yet the underlying physiological mechanisms are far from understood. Avian females are the heterogametic sex (ZW), and the future sex of the offspring is determined at chromosome segregation during meiosis I, shortly before the

Elevated mortality among birds in Chernobyl as judged from skewed age and sex ratios.

Directory of Open Access Journals (Sweden)

Anders Pape Møller

Full Text Available Radiation has negative effects on survival of animals including humans, although the generality of this claim is poorly documented under low-dose field conditions. Because females may suffer disproportionately from the effects of radiation on survival due to differences in sex roles during reproduction, radiation-induced mortality may result in male-skewed adult sex ratios.We estimated the effects of low-dose radiation on adult survival rates in birds by determining age ratios of adults captured in mist nets during the breeding season in relation to background radiation levels around Chernobyl and in nearby uncontaminated control areas. Age ratios were skewed towards yearlings, especially in the most contaminated areas, implying that adult survival rates were reduced in contaminated areas, and that populations in such areas could only be maintained through immigration from nearby uncontaminated areas. Differential mortality in females resulted in a strongly male-skewed sex ratio in the most contaminated areas. In addition, males sang disproportionately commonly in the most contaminated areas where the sex ratio was male skewed presumably because males had difficulty finding and acquiring mates when females were rare. The results were not caused by permanent emigration by females from the most contaminated areas because none of the recaptured birds had changed breeding site, and the proportion of individuals with morphological abnormalities did not differ significantly between the sexes for areas with normal and higher levels of contamination.These findings are consistent with the hypothesis that the adult survival rate of female birds is particularly susceptible to the effects of low-dose radiation, resulting in male skewed sex ratios at high levels of radiation. Such skewed age ratios towards yearlings in contaminated areas are consistent with the hypothesis that an area exceeding 30,000 km(2 in Chernobyl's surroundings constitutes an

Preconception maternal polychlorinated biphenyl concentrations and the secondary sex ratio

International Nuclear Information System (INIS)

Taylor, Kira C.; Jackson, Leila W.; Lynch, Courtney D.; Kostyniak, Paul J.; Buck Louis, Germaine M.

2007-01-01

The secondary sex ratio is the ratio of male to female live births and historically has ranged from 102 to 106 males to 100 females. Temporal declines have been reported in many countries prompting authors to hypothesize an environmental etiology. Blood specimens were obtained from 99 women aged 24-34 prior to attempting pregnancy and quantified for 76 polychlorinated biphenyl (PCB) congeners using dual column gas chromatography with electron capture detection. Women were prospectively followed until pregnancy or 12 cycles of trying. The odds of a male birth for three PCB groupings (total, estrogenic, anti-estrogenic) controlling for maternal characteristics were estimated using logistic regression. Among the 50 women with live births and PCB data, 26 female and 24 male infants were born (ratio 0.92). After adjusting for age and body mass index, odds of a male birth were elevated among women in the second (OR=1.29) and third (OR=1.48) tertiles of estrogenic PCBs; odds (OR=0.70) were reduced among women in the highest tertile of anti-estrogenic PCBs. All confidence intervals included one. The direction of the odds ratios in this preliminary study varied by PCB groupings, supporting the need to study specific PCB patterns when assessing environmental influences on the secondary sex ratio

Ownership of dwelling affects the sex ratio at birth in Uganda.

Directory of Open Access Journals (Sweden)

Bernard Wallner

Full Text Available BACKGROUND: Socio-economic conditions can affect the secondary sex ratio in humans. Mothers under good environmental conditions are predicted to increase the birth rates of sons according to the Trivers-Willard hypothesis (TWH. This study analyzed the effects of ownership and non-ownership of dwellings on the sex ratio at birth (SRB on a Ugandan sample. METHODOLOGY/PRINCIPAL FINDINGS: Our investigation included 438,640 mothers aged between 12 and 54 years. The overall average SRB was 0.5008. Mothers who live in owned dwellings gave increased births to sons (0.5019 compared to those who live in non-owned dwellings (0.458. Multivariate statistics revealed the strongest effects of dwelling ownership when controlling for demographic and social variables such as marital status, type of marriage, mothers' age, mothers' education, parity and others. CONCLUSIONS/SIGNIFICANCE: The results are discussed in the framework of recent plausible models dealing with the adjustment of the sex ratio. We conclude that the aspect of dwelling status could represent an important socio-economic parameter in relation to SRB variations in humans if further studies are able to analyze it between different countries in a comparative way.

Ownership of dwelling affects the sex ratio at birth in Uganda.

Science.gov (United States)

Wallner, Bernard; Fieder, Martin; Seidler, Horst

2012-01-01

Socio-economic conditions can affect the secondary sex ratio in humans. Mothers under good environmental conditions are predicted to increase the birth rates of sons according to the Trivers-Willard hypothesis (TWH). This study analyzed the effects of ownership and non-ownership of dwellings on the sex ratio at birth (SRB) on a Ugandan sample. Our investigation included 438,640 mothers aged between 12 and 54 years. The overall average SRB was 0.5008. Mothers who live in owned dwellings gave increased births to sons (0.5019) compared to those who live in non-owned dwellings (0.458). Multivariate statistics revealed the strongest effects of dwelling ownership when controlling for demographic and social variables such as marital status, type of marriage, mothers' age, mothers' education, parity and others. The results are discussed in the framework of recent plausible models dealing with the adjustment of the sex ratio. We conclude that the aspect of dwelling status could represent an important socio-economic parameter in relation to SRB variations in humans if further studies are able to analyze it between different countries in a comparative way.

Ownership of Dwelling Affects the Sex Ratio at Birth in Uganda

Science.gov (United States)

Wallner, Bernard; Fieder, Martin; Seidler, Horst

2012-01-01

Background Socio-economic conditions can affect the secondary sex ratio in humans. Mothers under good environmental conditions are predicted to increase the birth rates of sons according to the Trivers-Willard hypothesis (TWH). This study analyzed the effects of ownership and non-ownership of dwellings on the sex ratio at birth (SRB) on a Ugandan sample. Methodology/Principal Findings Our investigation included 438,640 mothers aged between 12 and 54 years. The overall average SRB was 0.5008. Mothers who live in owned dwellings gave increased births to sons (0.5019) compared to those who live in non-owned dwellings (0.458). Multivariate statistics revealed the strongest effects of dwelling ownership when controlling for demographic and social variables such as marital status, type of marriage, mothers’ age, mothers’ education, parity and others. Conclusions/Significance The results are discussed in the framework of recent plausible models dealing with the adjustment of the sex ratio. We conclude that the aspect of dwelling status could represent an important socio-economic parameter in relation to SRB variations in humans if further studies are able to analyze it between different countries in a comparative way. PMID:23284697

Kin discrimination and sex ratios in a parasitoid wasp

NARCIS (Netherlands)

Reece, S.E.; Shuker, D.M.; Pen, I.R.; Duncan, A.B.; Choudhary, A.; Batchelor, C.M.; West, S.A.

Sex ratio theory provides a clear and simple way to test if nonsocial haplodiploid wasps can discriminate between kin and nonkin. Specifically, if females can discriminate siblings from nonrelatives, then they are expected to produce a higher proportion of daughters if they mate with a sibling. This

Thermal fluctuation within nests and predicted sex ratio of Morelet's Crocodile.

Science.gov (United States)

Escobedo-Galván, Armando H; López-Luna, Marco A; Cupul-Magaña, Fabio G

2016-05-01

Understanding the interplay between thermal variations and sex ratio in reptiles with temperature-dependent sex determination is the first step for developing long-term conservation strategies. In case of crocodilians, the information is fragmentary and insufficient for establishing a general framework to consider how thermal fluctuation influence sex determination under natural conditions. The main goal of this study was to analyze thermal variation in nests of Crocodylus moreletii and to discuss the potential implications for predicting offspring sex ratio. The study was carried out at the Centro de Estudios Tecnológicos del Mar N° 2 and at the Sistemas Productivos Cocodrilo, Campeche, Mexico. Data was collected in the nesting season of Morelet's Crocodiles during three consecutive seasons (2007-2009). Thermal fluctuations for multiple areas of the nest chamber were registered by data loggers. We calculate the constant temperature equivalent based on thermal profiles among nests to assess whether there are differences between the nest temperature and its equivalent to constant temperature. We observed that mean nest temperature was only different among nests, while daily thermal fluctuations vary depending on the depth position within the nest chamber, years and nests. The constant temperature equivalent was different among and within nests, but not among survey years. We observed differences between constant temperature equivalent and mean nest temperature both at the top and in the middle of the nest cavities, but were not significantly different at the bottom of nest cavities. Our results enable examine and discuss the relevance of daily thermal fluctuations to predict sex ratio of the Morelet's Crocodile. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sex Ratio and Twinning in Women with Hyperemesis or Pre-eclampsia

DEFF Research Database (Denmark)

Basso, Olga; Olsen, Jørn

2001-01-01

We examined twinning and fetal gender in births of women with a hospital diagnosis of pre-eclampsia or hyperemesis. We also investigated sex ratio in infants whose mothers had had hyperemesis or pre-eclampsia in a different pregnancy. From all the hospitalized cases in Denmark between 1980 and 1996...... we extracted 6,227 births with hyperemesis and 24,764 with pre-eclampsia. Twins were more frequent in pregnancies with either condition. The male to female sex ratio was 1.04 (95%CI = 1.02-1.05) in the reference population, 0.87 (95% CI = 0.82-0.91) in births with hyperemesis, and 1.10 (95% CI = 1...

Human semen quality and the secondary sex ratio.

Science.gov (United States)

Bae, Jisuk; Kim, Sungduk; Chen, Zhen; Eisenberg, Michael L; Buck Louis, Germaine M

2017-01-01

The aim of this study was to evaluate the association between semen quality and the secondary sex ratio (SSR), defined as the ratio of male to female live births. Our study cohort comprised 227 male partners who were enrolled prior to conception in Michigan and Texas between 2005 and 2009, and prospectively followed through delivery of a singleton birth. The male partners provided a baseline and a follow-up semen sample a month apart. Semen analysis was conducted to assess 27 parameters including five general characteristics, six sperm head measures, 14 morphology measures, and two sperm chromatin stability assay measures. Modified Poisson regression models with a robust error variance were used to estimate the relative risk (RR) and 95% confidence interval (95% CI) of a male birth for each semen parameter, after adjusting for potential confounders. Of the 27 semen parameters, only the percentage of bicephalic sperm was significantly associated with the SSR (2 nd vs 1 st quartile, RR, 0.65, 95% CI, 0.45-0.95, P = 0.03; 4 th vs 1 st quartile, RR, 0.61, 95% CI, 0.38-1.00, P semen quality is associated with offspring sex determination.

The association between male-biased sex ratio and indicators of stress in red-spotted newts.

Science.gov (United States)

Aspbury, Andrea S; Grayson, Kristine L; Fantaye, Selamawit; Nichols, Ian; Myers-Burton, Miranda; Ortiz-Mangual, Xavier; Gabor, Caitlin R

2017-05-01

In populations with a male-biased operational sex ratio, coercive mating by males can have fitness consequences for females. One component of reduced fitness for females in populations with a male-biased OSR may be greater activation of the stress response, resulting in higher corticosterone release rates (CORT; a glucocorticoid stress hormone in amphibians). We test the hypothesis that a male-biased sex ratio affects female activity and release rates of CORT and testosterone (T) in male and female red-spotted newts (Notophthalmus viridescens). First, we evaluated if chemical cues from a male-biased sex ratio affect activity and CORT release rates in females. We predicted that females exposed to chemical cues of three males would be less active and have higher CORT release rates than those exposed to chemical cues of one male. Second, we measured CORT release rates of red-spotted newts in field enclosures with either a male-biased or a female-biased sex ratio. We predicted that females in the male-biased treatment would have higher CORT and T release rates than those in a female-biased treatment, owing to higher levels of male harassment. We also predicted that males would have higher CORT and T release rates in male-biased treatments due to higher levels of male-male competition. Females were not less active in response to chemical cues from more males over fewer males, but there was a positive relationship between female activity and CORT when they were exposed to the cues of three males. We also found that females, but not males, in the male-biased sex ratio treatment had higher CORT and T release rates than those in the female-biased treatment. Our results support the hypothesis that a male-biased sex ratio leads to a higher stress response, which may underlie the observed decrease in immune function and body condition in previous work exposing female red-spotted newts to a male-biased sex ratio. This study furthers our understanding of the mechanistic basis

Steroid Hormones and Female Energy Balance: Relation to Offspring Primary Sex Ratio

NARCIS (Netherlands)

Aslam, M.L.; Woelders, H.

2017-01-01

Birds can manipulate the offspring sex ratio under natural and experimental conditions. Various factors related to the avian mother, as well as her eggs, have been reported to be linked with the sex determination process. These factors appear to affect the chance of laying a male or female egg

Differences in Movement Pattern and Detectability between Males and Females Influence How Common Sampling Methods Estimate Sex Ratio.

Directory of Open Access Journals (Sweden)

João Fabrício Mota Rodrigues

Full Text Available Sampling the biodiversity is an essential step for conservation, and understanding the efficiency of sampling methods allows us to estimate the quality of our biodiversity data. Sex ratio is an important population characteristic, but until now, no study has evaluated how efficient are the sampling methods commonly used in biodiversity surveys in estimating the sex ratio of populations. We used a virtual ecologist approach to investigate whether active and passive capture methods are able to accurately sample a population's sex ratio and whether differences in movement pattern and detectability between males and females produce biased estimates of sex-ratios when using these methods. Our simulation allowed the recognition of individuals, similar to mark-recapture studies. We found that differences in both movement patterns and detectability between males and females produce biased estimates of sex ratios. However, increasing the sampling effort or the number of sampling days improves the ability of passive or active capture methods to properly sample sex ratio. Thus, prior knowledge regarding movement patterns and detectability for species is important information to guide field studies aiming to understand sex ratio related patterns.

Differences in Movement Pattern and Detectability between Males and Females Influence How Common Sampling Methods Estimate Sex Ratio.

Science.gov (United States)

Rodrigues, João Fabrício Mota; Coelho, Marco Túlio Pacheco

2016-01-01

Sampling the biodiversity is an essential step for conservation, and understanding the efficiency of sampling methods allows us to estimate the quality of our biodiversity data. Sex ratio is an important population characteristic, but until now, no study has evaluated how efficient are the sampling methods commonly used in biodiversity surveys in estimating the sex ratio of populations. We used a virtual ecologist approach to investigate whether active and passive capture methods are able to accurately sample a population's sex ratio and whether differences in movement pattern and detectability between males and females produce biased estimates of sex-ratios when using these methods. Our simulation allowed the recognition of individuals, similar to mark-recapture studies. We found that differences in both movement patterns and detectability between males and females produce biased estimates of sex ratios. However, increasing the sampling effort or the number of sampling days improves the ability of passive or active capture methods to properly sample sex ratio. Thus, prior knowledge regarding movement patterns and detectability for species is important information to guide field studies aiming to understand sex ratio related patterns.

Sex ratio of lambs born from assisted reproductive technologies ...

African Journals Online (AJOL)

The objective of the present study was to investigate sex ratio of offspring resulting from superstimulated donors from two different breeds and artificially inseminated ewes from three different breeds. Romanov (n = 5) and Charollais (n = 6) (2 - 7 years of age) donors were superovulated using FSH-p with 400 mg ...

The Relationship of Body Length and Ratio Pappilla with Sex in Gobi Fish (Sicyopterus macrostetholepis

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Rona Taula Sari

2017-07-01

Full Text Available Research about the relationship of body length and ratio papilla with sex in goby fish (S. macrostetholepis Blkr. has been done at Animal Structure and Developmental Laboratory, Biologi Department, Faculty of Matematics and Natural Sciences, Andalas University, Padang, which purposed to analyse the relationship of body length and ratio papilla with sex of goby fish (S. macrostetholepis Blkr.. The samples were taken in wild stream area at Batangkuranji river, Padang City. This research used descriptive method and data were analyzed by qualitatively and quantitatively. The results of investigation showed that in several goby fishes (S. macrostetholepis Blkr. with different sex had the same of body length and the same of ratio papilla. So, there was not relationship between of body length and ratio papilla with sex.  Goby fishes (S. macrostetholepis Blkr. it belongs to the hermaphrodite protogini, which the androgynous young females, while in adulthood, it would change sex to male. The results of this study are expected to add to the treasures of knowledge and information about reproductive gobies (S. macrostetholepis Blkr. in the preservation and development of fish farming.   

Secondary sex ratio in relation to exposures to polychlorinated biphenyls, dichlorodiphenyl dichloroethylene and methylmercury

DEFF Research Database (Denmark)

Timmermann, Clara Amalie Gade; Choi, Anna L; Petersen, Maria Skaalum

2017-01-01

This study was undertaken to assess the potential impact of maternal exposures to polychlorinated biphenyl (PCB), dichlorodiphenyl dichloroethylene (DDE) and methylmercury on the secondary sex ratios (the ratio of male to female live births) over a span of 23 years. The study includes prospective......% CI = 2-17%), respectively, of giving birth to a boy. In conclusion, maternal exposure to ΣPCB, DDE and methylmercury was associated with a slightly increased secondary sex ratio. The impact of paternal exposures could not be taken into account and deserves attention....

Variation in offspring sex ratio of a long-lived sexually dimorphic raptor, the eastern imperial eagle (Aquila heliaca)

Science.gov (United States)

Todd E. Katzner; Daniel S. Jackson; Jamie Ivy; Evgeny A. Bragin; Andrew Dewoody

2014-01-01

Sex ratio theory attempts to explain observed variation in offspring sex ratio at both the population and the brood levels. In the context of low-fecundity organisms producing high-investment offspring, the drivers of adaptive variation in sex ratio are incompletely understood. For raptors that display reverse sexual dimorphism (RSD), preferential allocation of...

SEASONAL-VARIATION IN THE SEX-RATIO OF MARSH HARRIER CIRCUS-AERUGINOSUS BROODS

NARCIS (Netherlands)

ZIJLSTRA, M; DAAN, S; BRUINENBERGRINSMA, J

1992-01-01

1. Analysis of the sexes of 2260 nestlings in 735 marsh harrier broods revealed an overall excess [sex ratio (SR) = 54.8%] of males, and a significant increase in the proportion of males with progressive laying date (d = day of the year): In [SR/(1-SR)] = -1.286 + 0.013 d. 2. We argue that it is

Seasonal variation in Eurasian Wigeon Anas penelope sex and age ratios from hunter-based surveys

DEFF Research Database (Denmark)

Clausen, Kevin Kuhlmann; Dalby, Lars; Sunde, Peter

2013-01-01

dominated by adult males, and juvenile proportions were highest in November and significantly lower before and after this peak. Nationwide field assessments undertaken in January 2012 showed no significant differences from sex and age ratios in the wing survey data from that particular hunting season (2011...... schemes. This study found consistent seasonal variation in Eurasian Wigeon Anas penelope sex and age ratios among Danish hunter-based wing surveys, and describes how accounting for this variation might explain reported discrepancies between this and other monitoring methods. Early season flocks were....../2012), indicating that this survey is a good predictor of Wigeon demography. These results highlight the need to account for consistent temporal variation in such demographic time series when using the results to model population parameters....

Sibling Sex Ratio and Birth Order in Early-Onset Gender Dysphoric Adolescents

NARCIS (Netherlands)

Schagen, S.E.E.; Delemarre-van de Waal, H.A.; Blanchard, R.; Cohen-Kettenis, P.T.

2012-01-01

Several sibship-related variables have been studied extensively in sexual orientation research, especially in men. Sibling sex ratio refers to the ratio of brothers to sisters in the aggregate sibships of a group of probands. Birth order refers to the probands' position (e.g., first-born,

Effect of Temperature on Reproduction and Sex Ratio of Guppy (Poecilia reticulata Peters)

OpenAIRE

H. Arfah; S. Mariam; . Alimuddin

2007-01-01

Water temperature could affect the reproduction of broodstock and sex ratio of progeny.  In this study, broodstock of guppy (Poecilia reticulata Peters) was reared in different temperature to determine its effect on reproduction of broodstock and sex ratio of their progeny. The result of study show that broodstock reared at 27°C produced more fry (16 males mean) than that of 30°C (10 males), while broodstock reared at 33°C produced no progeny.  Percentage of male fish produced by broodstock r...

[Paternal exposure to occupational electromagnetic radiation and sex ratio of the offspring: a meta-analysis].

Science.gov (United States)

Tong, Shu-Hui; Liu, Yi-Ting; Liu, Yang

2013-02-01

To investigate the association between paternal exposure to occupational electromagnetic radiation and the sex ratio of the offspring. We searched various databases, including PubMed, Embase, Cochrane Library, OVID, Bioscience Information Service (BIOSIS), China National Knowledge Infrastructure, VIP Database for Chinese Technical Periodicals and Wanfang Database, for the literature relevant to the association of paternal exposure to occupational electromagnetic radiation with the sex ratio of the offspring. We conducted a meta-analysis on their correlation using Stata 11.0. There was no statistically significant difference in the sex ratio between the offspring with paternal exposure to occupational electromagnetic radiation and those without (pooled OR = 1.00 [95% CI: 0.95 -1.05], P = 0.875). Subgroup analysis of both case-control and cohort studies revealed no significant difference (pooled OR = 1.03 [95% CI: 0.99 -1.08], P = 0.104 and pooled OR = 0.98 [95% CI: 0.99 -1.08], P = 0.186, respectively). Paternal exposure to occupational electromagnetic radiation is not correlated with the sex ratio of the offspring.

Maternal Eating Disorders Influence Sex Ratio at Birth

OpenAIRE

Bulik, Cynthia M; Von Holle, Ann; Gendall, Kelly; Kveim Lie, Kari; Hoffman, Elizabeth; Mo, Xiaofei; Torgersen, Leila; Reichborn-Kjennerud, Ted

2008-01-01

We explored sex ratio at birth, defined as the proportion of male live births, in women with anorexia nervosa, bulimia nervosa, binge eating disorder, and eating disorders not otherwise specified-purging type (EDNOS-P) relative to a referent group in a large population based sample of 38,340 pregnant women in Norway. Poisson regressions were adjusted for mother’s age, pre-pregnancy BMI, lifetime smoking status, maternal education, income, marital status, gestational age, and parity. Lower pro...

Sex ratios, mating frequencies and relative abundance of sympatric millipedes in the genus Chersastus (Diplopoda: Pachybolidae

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Mark Ian Cooper

2014-12-01

Full Text Available Three hypotheses exist for explaining climbing behavior in millipedes: 1 waterlogging, 2 detritus limiting, and 3 mate avoidance. Data of sex ratios, mating frequency and relative abundance are provided to suggest an alternative explanation for the pattern in sympatric forest millipedes. Sex ratio differences - from equality - were tested using a G-test comparing millipedes on and above ground. Mating frequencies were calculated based on the percentage of paired individuals. Relative abundance may correlate with male-biases in the sex ratios. All three factors suggest Chersastus inscriptus has a higher reproductive potential than C. anulatus. This is evidence for mating hotspots.

Sex ratio meiotic drive as a plausible evolutionary mechanism for hybrid male sterility.

Science.gov (United States)

Zhang, Linbin; Sun, Tianai; Woldesellassie, Fitsum; Xiao, Hailian; Tao, Yun

2015-03-01

Biological diversity on Earth depends on the multiplication of species or speciation, which is the evolution of reproductive isolation such as hybrid sterility between two new species. An unsolved puzzle is the exact mechanism(s) that causes two genomes to diverge from their common ancestor so that some divergent genes no longer function properly in the hybrids. Here we report genetic analyses of divergent genes controlling male fertility and sex ratio in two very young fruitfly species, Drosophila albomicans and D. nasuta. A majority of the genetic divergence for both traits is mapped to the same regions by quantitative trait loci mappings. With introgressions, six major loci are found to contribute to both traits. This genetic colocalization implicates that genes for hybrid male sterility have evolved primarily for controlling sex ratio. We propose that genetic conflicts over sex ratio may operate as a perpetual dynamo for genome divergence. This particular evolutionary mechanism may largely contribute to the rapid evolution of hybrid male sterility and the disproportionate enrichment of its underlying genes on the X chromosome--two patterns widely observed across animals.

Exposure to widespread environmental endocrine disrupting chemicals and human sperm sex ratio

International Nuclear Information System (INIS)

Jurewicz, Joanna; Radwan, Michał; Sobala, Wojciech; Radwan, Paweł; Jakubowski, Lucjusz; Wielgomas, Bartosz; Ligocka, Danuta; Brzeźnicki, Sławomir; Hanke, Wojciech

2016-01-01

In recent years, a trend toward a declining proportion of male births has been noted in several, but not all, industrialized countries. The underlying reason for the drop in the sex ratio is unclear, but one theory states that widespread environmental endocrine disrupting chemicals affecting the male reproductive system in a negative manner could be part of the explanation. The present study was designed to investigate whether the urinary phthalate, pyrethroids and polycyclic aromatic hydrocarbons metabolites concentrations were associated with sperm Y:X ratio. The study population consisted of 194 men aged under 45 years of age who attended infertility clinic in Lodz, Poland for diagnostic purposes with normal semen concentration of 20–300 mln/ml or with slight oligozoospermia (semen concentration of 15–20 mln/ml) (WHO, 1999). The Y:X ratio was assessed by fluorescent in situ hybridization. Urinary concentrations of 1-hydroxypyrene were measured by high performance liquid chromatography, phthalate metabolites were analyzed using a procedure based on the LC-MS/MS methods and metabolites of synthetic pyrethroids were assessed by gas chromatography ion-tap mass spectrometry method. After adjustment for potential confounders (past diseases, age, abstinence, smoking, alcohol consumption, sperm concentration, motility, morphology) 5OH MEHP, CDCCA to TDCCA and 1-OHP was negatively related to Y:X sperm chromosome ratio (p = 0.033, p < 0.001, p = 0.047 respectively). As this is the first study to elucidate the association between the level of metabolites of widespread environmental endocrine disrupting chemicals (phthalates, synthetic pyrethroids, polycyclic aromatic hydrocarbons) on sex chromosome ratio in sperm therefore, these findings require further replication in other populations. - Highlights: • Urinary phthalate metabolites levels were significantly associated with a decrease in Y/X chromosome bearing sperm. • The levels of 1-hydroxypyrene in urine

Female starlings adjust primary sex ratio in response to aromatic plants in the nest.

Science.gov (United States)

Polo, Vicente; Veiga, José P; Cordero, Pedro J; Viñuela, Javier; Monaghan, Pat

2004-09-22

Adjustment of offspring sex ratios should be favoured by natural selection when parents are capable of facultatively altering brood sex ratios and of recognizing the circumstances that predict the probable fitness benefit of producing sons and daughters. Although experimental studies have shown that female birds may adjust offspring sex ratios in response to changes in their own condition and in the external appearance of their mate, and male attributes other than his external morphology are also thought to act as signals of male quality, it is not known whether females will respond to changes in such signals, in the absence of any change in the appearance of the male himself. Here, we experimentally manipulated a male courtship display, the green plants carried to the nest by male spotless starlings (Sturnus unicolor), without changing any physical attributes of the male himself, and examined whether this influenced female decisions on offspring sex ratio. We found that in an environment in which female starlings were producing more daughters than sons, experimental enhancement of the green nesting material caused females to significantly increase the number of male eggs produced and thereby removed the female bias. This effect was consistent in 2 years and at two localities. This demonstrates that the green material, whose function has long puzzled biologists, conveys important information to the female and that she facultatively adjusts offspring production accordingly.

Flow cytometric sexing of spider sperm reveals an equal sperm production ratio in a female-biased species

DEFF Research Database (Denmark)

Vanthournout, Bram; Deswarte, K; Hammad, H

2014-01-01

research. Pinpointing the underlying mechanism of sex ratio bias is challenging owing to the multitude of potential sex ratio-biasing factors. In the dwarf spider, Oedothorax gibbosus, infection with the bacterial endosymbiont Wolbachia results in a female bias. However, pedigree analysis reveals...

The Sex Ratio of Full and Half Siblings of People Diagnosed With ADHD in Childhood and Adolescence

DEFF Research Database (Denmark)

Mouridsen, Svend Erik Birkebæk; Rich, Bente; Isager, Torben

2014-01-01

Objective:It has been suggested that high levels of prenatal testosterone exposure are implied in the etiology of male preponderance disorders such as autism spectrum disorder and ADHD. Within this scope, we studied the sex ratio (proportion of males) in siblings of individuals diagnosed with ADHD...... in childhood and adolescence. Method: We did a nationwide, register-based cohort study of the sex ratio in siblings of the 16,381 patients in Denmark diagnosed with ADHD at age 17 years and younger and registered in the nationwide Danish Psychiatric Central Register between January 1, 1994 and May 28, 2013....... Results: Among the 33,151 siblings, 17,041 were males and 16,110 females. This yields a sex ratio of 0.514, which is not statistically significant different from the Danish live birth sex ratio of 0.513 during the relevant years (p = .70). Conclusion: These findings provide no support for the hypothesis...

Sex ratio of five species of pelagic copepods from Indian Ocean

Digital Repository Service at National Institute of Oceanography (India)

Saraswathy, M.; Santhakumari, V.

Sex ratio in five species from south and southeast coast of India varied remarkably. Five species were selected for the present investigation. Range in the percentage of males was from 8 to 121 in @iUndinula vulgaris@@ (Dana), 16-425 in @i...

Explaining the Rapid Increase in Nigeria's Sex Ratio at Birth: Factors and Implications.

Science.gov (United States)

Kaba, Amadu J

2015-06-01

This paper examines the rapid increase in Nigeria's sex ratio at birth from 1.03 boys born for every 1 girl born in each year from 1996-2008 to 1.06 in each year from 2009-2014, second only to Tunisia in Africa at 1.07. The average sex ratio at birth in the world in 2014 was 1.07. In most Black African nations or Black majority nations, it is 1.03 or less. Among the factors presented for this development are: historical fluctuations of sex ratio at birth; geography and ethnicity; male preference/chasing a son; Age of parents; high death rates of male infants and males in general; and wealth/socioeconomic status. Among the potential implications are: young and poor men in Nigeria may not be able to find brides and form families due to a potential shortage of females; emigration of young and poor Nigerian men to West (Africa) and elsewhere to seek brides and form families; immigration of marriage age women from West (Africa) and around the world to Nigeria to seek husbands; and low contraceptive use and high fertility rates in Nigeria.

Sex ratio meiotic drive as a plausible evolutionary mechanism for hybrid male sterility.

Directory of Open Access Journals (Sweden)

Linbin Zhang

2015-03-01

Full Text Available Biological diversity on Earth depends on the multiplication of species or speciation, which is the evolution of reproductive isolation such as hybrid sterility between two new species. An unsolved puzzle is the exact mechanism(s that causes two genomes to diverge from their common ancestor so that some divergent genes no longer function properly in the hybrids. Here we report genetic analyses of divergent genes controlling male fertility and sex ratio in two very young fruitfly species, Drosophila albomicans and D. nasuta. A majority of the genetic divergence for both traits is mapped to the same regions by quantitative trait loci mappings. With introgressions, six major loci are found to contribute to both traits. This genetic colocalization implicates that genes for hybrid male sterility have evolved primarily for controlling sex ratio. We propose that genetic conflicts over sex ratio may operate as a perpetual dynamo for genome divergence. This particular evolutionary mechanism may largely contribute to the rapid evolution of hybrid male sterility and the disproportionate enrichment of its underlying genes on the X chromosome--two patterns widely observed across animals.

WormGender - Open-Source Software for Automatic Caenorhabditis elegans Sex Ratio Measurement.

Directory of Open Access Journals (Sweden)

Marta K Labocha

Full Text Available Fast and quantitative analysis of animal phenotypes is one of the major challenges of current biology. Here we report the WormGender open-source software, which is designed for accurate quantification of sex ratio in Caenorhabditis elegans. The software functions include, i automatic recognition and counting of adult hermaphrodites and males, ii a manual inspection feature that enables manual correction of errors, and iii flexibility to use new training images to optimize the software for different imaging conditions. We evaluated the performance of our software by comparing manual and automated assessment of sex ratio. Our data showed that the WormGender software provided overall accurate sex ratio measurements. We further demonstrated the usage of WormGender by quantifying the high incidence of male (him phenotype in 27 mutant strains. Mutants of nine genes (brc-1, C30G12.6, cep-1, coh-3, him-3, him-5, him-8, skr-1, unc-86 showed significant him phenotype. The WormGender is written in Java and can be installed and run on both Windows and Mac platforms. The source code is freely available together with a user manual and sample data at http://www.QuantWorm.org/. The source code and sample data are also available at http://dx.doi.org/10.6084/m9.figshare.1541248.

Masculine sex ratios, population age structure and the potential spread of HIV in China

Directory of Open Access Journals (Sweden)

M. Giovanna Merli

2010-01-01

Full Text Available There is much speculation regarding the contribution of China's changing demography to the spread of HIV/AIDS. We employ a bio-behavioral macrosimulation model of the heterosexual spread of HIV/AIDS to evaluate the roles that China's unique demographic conditions -- (1 masculine sex ratios at birth and (2 a population age structure that reflects rapid fertility decline since the 1970's -- play in altering the market for sexual partners, thereby potentially fueling an increase in behaviors associated with greater risk of HIV infection. We first simulate the relative contributions of the sex ratio at birth and the population age structure to the oversupply of males in the market for sexual partners and show that the sex ratio at birth only aggravates the severe oversupply of males which is primarily a consequence of the population age structure. We then examine the potential consequences of this demographic distortion for the spread of HIV infection and show that, to the extent that males adapt to the dearth of suitable female partners by seeking unprotected sexual contacts with female sex workers, the impact of the oversupply of males in the sexual partnership market on the spread of HIV will be severe.

Sex differences in cerebral venous thrombosis: A systematic analysis of a shift over time

NARCIS (Netherlands)

Zuurbier, Susanna M.; Middeldorp, Saskia; Stam, Jan; Coutinho, Jonathan M.

2016-01-01

In contemporary studies, cerebral venous thrombosis is three times more common in adult women than in men. To study the change in sex ratio over time in cerebral venous thrombosis. We systematically reviewed the literature. Any type of study with at least 40 patients with cerebral venous thrombosis

Population structure and the evolution of sexual size dimorphism and sex ratios in an insular population of Florida box turtles (Terrapene carolina bauri)

Science.gov (United States)

Dodd, C.K.

1997-01-01

Hypotheses in the chelonian literature suggest that in species with sexual size dimorphism, the smaller sex will mature at a smaller size and a younger age than the larger sex, sex ratios should be biased in favor of the earlier maturing sex, and deviations from a 1:1 sex ratio result from maturation of the smaller sex at a younger age. I tested these hypotheses using data collected from 1991 to 1995 on an insular (Egmont Key) population of Florida box turtles, Terrapene carolina bauri. Contrary to predictions, the earlier maturing sex (males) grew to larger sizes than the late maturing sex. Males were significantly larger than females in mean carapace length but not mean body mass. Sex ratios were not balanced, favoring the earlier maturing sex (1.6 males:1 female), but the sex-ratio imbalance did not result from faster maturation of the smaller sex. The imbalance in the sex ratio in Egmont Key's box turtles is not the result of sampling biases; it may result from nest placement. Size-class structure and sex ratios can provide valuable insights into the status and trends of populations of long-lived turtles.

Impaired imprinted X chromosome inactivation is responsible for the skewed sex ratio following in vitro fertilization

Science.gov (United States)

Tan, Kun; An, Lei; Miao, Kai; Ren, Likun; Hou, Zhuocheng; Tao, Li; Zhang, Zhenni; Wang, Xiaodong; Xia, Wei; Liu, Jinghao; Wang, Zhuqing; Xi, Guangyin; Gao, Shuai; Sui, Linlin; Zhu, De-Sheng; Wang, Shumin; Wu, Zhonghong; Bach, Ingolf; Chen, Dong-bao; Tian, Jianhui

2016-01-01

Dynamic epigenetic reprogramming occurs during normal embryonic development at the preimplantation stage. Erroneous epigenetic modifications due to environmental perturbations such as manipulation and culture of embryos during in vitro fertilization (IVF) are linked to various short- or long-term consequences. Among these, the skewed sex ratio, an indicator of reproductive hazards, was reported in bovine and porcine embryos and even human IVF newborns. However, since the first case of sex skewing reported in 1991, the underlying mechanisms remain unclear. We reported herein that sex ratio is skewed in mouse IVF offspring, and this was a result of female-biased peri-implantation developmental defects that were originated from impaired imprinted X chromosome inactivation (iXCI) through reduced ring finger protein 12 (Rnf12)/X-inactive specific transcript (Xist) expression. Compensation of impaired iXCI by overexpression of Rnf12 to up-regulate Xist significantly rescued female-biased developmental defects and corrected sex ratio in IVF offspring. Moreover, supplementation of an epigenetic modulator retinoic acid in embryo culture medium up-regulated Rnf12/Xist expression, improved iXCI, and successfully redeemed the skewed sex ratio to nearly 50% in mouse IVF offspring. Thus, our data show that iXCI is one of the major epigenetic barriers for the developmental competence of female embryos during preimplantation stage, and targeting erroneous epigenetic modifications may provide a potential approach for preventing IVF-associated complications. PMID:26951653

How do sex ratios in China influence marriage decisions and intra-household resource allocation?

Science.gov (United States)

Porter, Maria

2016-06-01

This article examines how imbalanced sex ratios influence marriage decisions and household bargaining. Using data from the 1982 Chinese census, the traditional "availability ratio" is modified to reflect the degree to which men tend to marry women from different cohorts. This ratio reflects the average tendency of men to prefer women who are close in age to women who are several years younger than them by weighting cohort sizes using the proportion of people in the population who marry someone born in a different cohort. Given that men generally marry younger women, this ratio varies independently of the size of one's own birth cohort. Yet, the ratio fluctuates considerably across individuals, as the sizes of birth cohorts in China vary across time and regions. This enables us to examine how variability in such ratios may influence marriage decisions and household bargaining. The findings suggest that women exercise greater bargaining power once married. Results indicate that as women become scarcer in the marriage market, they have healthier sons. Men also delay marriage, and consume less tobacco and alcohol. This paper also highlights how sensitive findings may be to using this modified weighted availability ratio rather than a traditional unweighted availability ratio.

Effects of larval-juvenile treatment with perchlorate and co-treatment with thyroxine on zebrafish sex ratios

Science.gov (United States)

Mukhi, S.; Torres, L.; Patino, R.

2007-01-01

The objective of this study was to determine the effect of larval-juvenile exposure to perchlorate, a thyroid hormone synthesis inhibitor, on the establishment of gonadal sex ratios in zebrafish. Zebrafish were exposed to untreated water or water containing perchlorate at 100 or 250 ppm for a period of 30 days starting at 3 days postfertilization (dpf). Recovery treatments consisted of a combination of perchlorate and exogenous thyroxine (T4; 10 nM). Thyroid histology was assessed at the end of the treatment period (33 dpf), and gonadal histology and sex ratios were determined in fish that were allowed an additional 10-day period of growth in untreated water. As expected, exposure to perchlorate caused changes in thyroid histology consistent with hypothyroidism and these effects were reversed by co-treatment with exogenous T4. Perchlorate did not affect fish survival but co-treatment with T4 induced higher mortality. However, relative to the corresponding perchlorate concentration, co-treatment with T4 caused increased mortality only at a perchlorate concentration of 100 ppm. Perchlorate alone or in the presence of T4 suppressed body length at 43 dpf relative to control values. Perchlorate exposure skewed the sex ratio toward female in a concentration-dependent manner, and co-treatment with T4 not only blocked the feminizing effect of perchlorate but also overcompensated by skewing the sex ratio towards male. Moreover, co-treatment with T4 advanced the onset of spermatogenesis in males. There was no clear association between sex ratios and larval survival or growth. We conclude that endogenous thyroid hormone plays a role in the establishment of gonadal sex phenotype during early development in zebrafish. ?? 2006 Elsevier Inc. All rights reserved.

Effect of Temperature on Reproduction and Sex Ratio of Guppy (Poecilia reticulata Peters

Directory of Open Access Journals (Sweden)

H. Arfah

2007-01-01

Full Text Available Water temperature could affect the reproduction of broodstock and sex ratio of progeny.  In this study, broodstock of guppy (Poecilia reticulata Peters was reared in different temperature to determine its effect on reproduction of broodstock and sex ratio of their progeny. The result of study show that broodstock reared at 27°C produced more fry (16 males mean than that of 30°C (10 males, while broodstock reared at 33°C produced no progeny.  Percentage of male fish produced by broodstock reared at 30°C is higher than that of 27°C.  Incubation time of embryo before birth is sorter in broodstock reared at 30°C (4-12 days compared with 27°C (18-22 days.  However, several progeny of broodstock reared at 30°C had abnormal vertebrae. Keywords: guppy, Poecilia reticulata, sex reversal, reproduction, monosex   ABSTRAK Suhu air inkubasi diduga dapat mempengaruhi reproduksi induk ikan dan nisbah kelamin keturunannya.  Pada penelitian ini, induk ikan gapi (Poecilia reticulata Peters dipelihara pada suhu 27°C, 30°C dan suhu 33°C untuk mengetahui pengaruhnya terhadap reproduksi dan rasio kelamin keturunannya.  Hasil penelitian menunjukkan bahwa induk ikan gapi yang dipelihara pada suhu 27°C menghasilkan anak lebih banyak (rata-rata 16 ekor daripada di suhu 30°C (10 ekor, sementara induk gagal melahirkan pada suhu pemeliharaan 33°C. Proporsi anak jantan yang dihasilkan oleh induk yang dipelihara pada suhu 30°C lebih banyak dibandingkan pada suhu 27°C.  Waktu inkubasi embrio sebelum dilahirkan oleh induk yang dipelihara pada suhu 30°C lebih singkat, yaitu 4-12 hari, dibandingkan pada  suhu 27°C, 18-22 hari.  Namun demikian beberapa anak ikan yang lahir dari induk yang dipelihara pada suhu suhu 30°C mengalami abnormalitas pada bagian tulang belakangnya.  Kata kunci: ikan gapi, Poecilia reticulata, sex reversal, reproduksi, monoseks

Sex-specific effects of altered competition on nestling growth and survival: an experimental manipulation of brood size and sex ratio.

Science.gov (United States)

Nicolaus, Marion; Michler, Stephanie P M; Ubels, Richard; van der Velde, Marco; Komdeur, Jan; Both, Christiaan; Tinbergen, Joost M

2009-03-01

1. An increase of competition among adults or nestlings usually negatively affects breeding output. Yet little is known about the differential effects that competition has on the offspring sexes. This could be important because it may influence parental reproductive decisions. 2. In sexual size dimorphic species, two main contradictory mechanisms are proposed regarding sex-specific effects of competition on nestling performance assuming that parents do not feed their chicks differentially: (i) the larger sex requires more resources to grow and is more sensitive to a deterioration of the rearing conditions ('costly sex hypothesis'); (ii) the larger sex has a competitive advantage in intra-brood competition and performs better under adverse conditions ('competitive advantage hypothesis'). 3. In the present study, we manipulated the level of sex-specific sibling competition in a great tit population (Parus major) by altering simultaneously the brood size and the brood sex ratio on two levels: the nest (competition for food among nestlings) and the woodlot where the parents breed (competition for food among adults). We investigated whether altered competition during the nestling phase affected nestling growth traits and survival in the nest and whether the effects differed between males, the larger sex, and females. 4. We found a strong negative and sex-specific effect of experimental brood size on all the nestling traits. In enlarged broods, sexual size dimorphism was smaller which may have resulted from biased mortality towards the less competitive individuals i.e. females of low condition. No effect of brood sex ratio on nestling growth traits was found. 5. Negative brood size effects on nestling traits were stronger in natural high-density areas but we could not confirm this experimentally. 6. Our results did not support the 'costly sex hypothesis' because males did not suffer from higher mortality under harsh conditions. The 'competitive advantage hypothesis' was

Digit Ratio (2D:4D): A Biomarker for Prenatal Sex Steroids and Adult Sex Steroids in Challenge Situations.

Science.gov (United States)

Manning, John; Kilduff, Liam; Cook, Christian; Crewther, Blair; Fink, Bernhard

2014-01-01

Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. This ratio is considered to be a biomarker of the balance between fetal testosterone (T) and estrogen (E) in a narrow window of early ontogeny. Evidence for this assertion is derived from direct and indirect measures of prenatal hormonal exposure (in experimental animals, via amniotic fluid samples and in the study of sex-typical traits) in relation to 2D:4D. In contrast, the relationships between 2D:4D and levels of sex steroids in adults are less clear, as many correlational studies of 2D:4D and adult sex steroids have concluded that this association is statistically non-significant. Here, we suggest that in order to understand the link between 2D:4D and sex hormones, one must consider both fetal organizing and adult activating effects of T and E. In particular, we hypothesize that 2D:4D correlates with organizing effects on the endocrine system that moderate activating effects in adulthood. We argue that this is particularly evident in "challenging" conditions such as aggressive and sexual encounters, in which individuals show increased levels of T. We discuss this refinement of the 2D:4D paradigm in relation to the links between 2D:4D and sports performance, and aggression.

Missing girls in India: infanticide, feticide and made-to-order pregnancies? Insights from hospital-based sex-ratio-at-birth over the last century.

Science.gov (United States)

Sahni, Mohit; Verma, Neeraj; Narula, D; Varghese, Raji Mathew; Sreenivas, V; Puliyel, Jacob M

2008-05-21

There are 44 million missing women in India. Gender bias; neglect of girls, infanticides and feticides are responsible. The sex ratio at birth can be used to examine the influence of antenatal sex selection on the sex ratio. Records from 321,991 deliveries at one hospital over 11 decades were utilized. The middle year in each decade was taken as representative of the decade. Data from 33,524 deliveries were then analyzed. Data for each decade was combined with that of previous decades and compared to the data of subsequent decades to look for any change in the trend. Sex ratio in the second children against sex of the first child was studied separately. The mean sex ratio for the 110 years examined was 910 girls to 1000 boys (95% CI; 891 to 930). The sex ratio dropped significantly from 935 (CI: 905 to 967) before 1979, to 892 (CI: 868 to 918) after 1980 (P = 0.04). The sex ratio in the second child was significantly lower if the first child was a girl [716 (CI: 672 to 762] (Psex ratio fell significantly after 1980 when ultra sound machines for antenatal sex determination became available. The sex ratio in second children if the first was a girl was even lower. Sex selective abortions after antenatal sex determination are thus implicated. However data on second children especially the excess of girls born to mothers who have a previous boy seen in the decade before the advent of antenatal ultra sound machines, suggests that other means of sex selection are also used.

High sex ratios in rural China: declining well-being with age in never-married men.

Science.gov (United States)

Zhou, Xudong; Hesketh, Therese

2017-09-19

In parts of rural China male-biased sex ratios at birth, combined with out-migration of women, have led to highly male-biased adult sex ratios, resulting in large numbers of men being unable to marry, in a culture where marriage and reproduction are an expectation. The aim of this study was to test the hypotheses that older unmarried men are more predisposed to depression, low self-esteem and aggression than both those who are married, and those who are younger and unmarried. Self-completion questionnaires were administered among men aged 20-40 in 48 villages in rural Guizhou province, southwestern China. Tools used included the Beck Depression Inventory, the Rosenberg's Self-esteem Scale and the Bryant-Smith Aggression Questionnaire. Regression models assessed psychological wellbeing while adjusting for socio-demographic variables. Completed questionnaires were obtained from 957 never-married men, 535 married men aged 30-40, 394 partnered men and 382 unpartnered men aged 20-29. After adjusting for socio-demographic variables, never-married men were more predisposed to depression ( p self-esteem ( p < 0.05) and suicidal tendencies ( p < 0.001). All the psychological measures deteriorated with age in never-married men. In contrast, married men remained stable on these dimensions with age. Never-married men are a psychologically highly vulnerable group in a society where marriage is an expectation. Since the highest birth sex-ratio cohorts have not yet reached reproductive age, the social tragedy of these men will last for at least another generation.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'. © 2017 The Authors.

Parallel distribution of sexes within left and right uterine horns in Holstein dairy cows: evidence that the effect of side of pregnancy on sex ratio could be breed-specific in cattle.

Science.gov (United States)

Gharagozlou, F; Vojgani, M; Akbarinejad, V; Niasari-Naslaji, A; Hemmati, M; Youssefi, R

2013-11-30

Dissimilar distribution of male and female calves within left and right uterine horns has been observed in beef cows. A retrospective study was conducted to investigate the effect of side of pregnancy on secondary sex ratio in Holstein dairy cows. Data associated with sex of calves, side of pregnancy, sire, dam, parity number of dam, AI technician, season and year were retrieved from the database of a Holstein dairy farm. In total, data consisted of 6515 birth records from 3155 dams and 244 sires across years 2001-2010. Data were analyzed using logistic regression. There was no difference in proportion of male and female calves between left (52.9% and 47.1%, respectively) and right (53.2% and 46.8%, respectively) uterine horns (P>0.05). AI technician, year, season and parity of dam did not affect secondary sex ratio (P>0.05). Secondary sex ratio of left and right uterine horns, and consequently, overall secondary sex ratio (53.1%) were skewed toward males as compared with hypothetical secondary sex ratio of 50% (Pcows. Copyright © 2013 Elsevier B.V. All rights reserved.

The Facial Width-to-Height Ratio Predicts Sex Drive, Sociosexuality, and Intended Infidelity.

Science.gov (United States)

Arnocky, Steven; Carré, Justin M; Bird, Brian M; Moreau, Benjamin J P; Vaillancourt, Tracy; Ortiz, Triana; Marley, Nicole

2017-09-19

Previous research has linked the facial width-to-height ratio (FWHR) to a host of psychological and behavioral characteristics, primarily in men. In two studies, we examined novel links between FWHR and sex drive. In Study 1, a sample of 145 undergraduate students revealed that FWHR positively predicted sex drive. There were no significant FWHR × sex interactions, suggesting that FWHR is linked to sexuality among both men and women. Study 2 replicated and extended these findings in a sample of 314 students collected from a different Canadian city, which again demonstrated links between the FWHR and sex drive (also in both men and women), as well as sociosexuality and intended infidelity (men only). Internal meta-analytic results confirm the link between FWHR and sex drive among both men and women. These results suggest that FWHR may be an important morphological index of human sexuality.

Does the sex ratio at sexual maturity affect men's later-life mortality risks? Evidence from historical China.

Science.gov (United States)

Zang, Emma; Zheng, Hui

2018-04-01

This study examines the relationship between the male-to-female sex ratio (measured as the proportion male) at sexual maturity and later-life mortality risks in the context of pre-industrial northeast China, using registration data from the Qing Dynasty. We find that a higher male-to-female sex ratio at sexual maturity is associated with a higher later-life mortality risk among men. This association is likely due to the long-term adverse consequences of stress caused by low mate availability at sexual maturity. We further find that a high sex ratio at sexual maturity mitigates the health benefits of marriage and exacerbates the health disadvantages of holding an official position in Qing China. Copyright © 2018 Elsevier Ltd. All rights reserved.

Missing Girls in India: Infanticide, Feticide and Made-to-Order Pregnancies? Insights from Hospital-Based Sex-Ratio-at-Birth over the Last Century

Science.gov (United States)

Sahni, Mohit; Verma, Neeraj; Narula, D.; Varghese, Raji Mathew; Sreenivas, V.; Puliyel, Jacob M.

2008-01-01

Background There are 44 million missing women in India. Gender bias; neglect of girls, infanticides and feticides are responsible. The sex ratio at birth can be used to examine the influence of antenatal sex selection on the sex ratio. Materials and Methods Records from 321,991 deliveries at one hospital over 11 decades were utilized. The middle year in each decade was taken as representative of the decade. Data from 33,524 deliveries were then analyzed. Data for each decade was combined with that of previous decades and compared to the data of subsequent decades to look for any change in the trend. Sex ratio in the second children against sex of the first child was studied separately. Results The mean sex ratio for the 110 years examined was 910 girls to 1000 boys (95% CI; 891 to 930). The sex ratio dropped significantly from 935 (CI: 905 to 967) before 1979, to 892 (CI: 868 to 918) after 1980 (P = 0.04). The sex ratio in the second child was significantly lower if the first child was a girl [716 (CI: 672 to 762] (P<0.001). On the other hand, there was an excess of girls born to mothers whose first child was boy [1140 girls per 1000 boys (CI: 1072 to 1212 P<0.001)]. Conclusions The sex ratio fell significantly after 1980 when ultra sound machines for antenatal sex determination became available. The sex ratio in second children if the first was a girl was even lower. Sex selective abortions after antenatal sex determination are thus implicated. However data on second children especially the excess of girls born to mothers who have a previous boy seen in the decade before the advent of antenatal ultra sound machines, suggests that other means of sex selection are also used. PMID:18493614

Sex Ratio And Size At First Maturity Of Blue Swimming Crab (Portunus pelagicus Salemo Island Pangkep Regency

Directory of Open Access Journals (Sweden)

Muh. Saleh Nurdin

2016-03-01

Full Text Available Blue swimming crab (Portunuspelagicus is aeconomical valuable fisheries importantcommodity  due to the high demand and availability jobs created for the fishermen. Due to their high demand blue swimming crab heavily exploited from Salemo Island. This study aimed at comparing the sex ratio and the size at first maturity of blue swimming crab caught in mangrove ecosystems, coral reefs, and seagrass. Sex ratio was analyzed using chi square test and the size at first maturity was analyzed using the Spearman-Karber formula. The results showed the sex ratio ofmales and femalessmall crab caught in every ecosystem is balanced. The size at first maturity of blue swimming crab caught in mangrove, seagrass and coral reefs, each to the male 81,08 mm, 102,36 mm and 102,87 mm in width and size of female 94,54 mm, 83,35 mm, 98,31 mm width. In a reference to government regulations, the blue male swimming crab caught in the coral reef and seagrass ecosystems have yet to size at first maturity is allowed to be captured. Keywords: blue swimming crab, sex ratio,size at first maturity, Salemo Island

The Effects of Sex-Ratio and Density on Locomotor Activity in the House Fly, Musca domestica

OpenAIRE

Bahrndorff, Simon; Kjærsgaard, Anders; Pertoldi, Cino; Loeschcke, Volker; Schou, Toke M.; Skovgård, Henrik; Hald, Birthe

2012-01-01

Although locomotor activity is involved in almost all behavioral traits, there is a lack of knowledge on what factors affect it. This study examined the effects of sex-ratio and density on the circadian rhythm of locomotor activity of adult Musca domestica L. (Diptera: Muscidae) using an infra-red light system. Sex-ratio significantly affected locomotor activity, increasing with the percentage of males in the vials. In accordance with other studies, males were more active than females, but th...

Marriage season, promptness of successful pregnancy and first-born sex ratio in a historical natural fertility population - evidence for sex-dependent early pregnancy loss?

Science.gov (United States)

Nonaka, K.; Desjardins, Bertrand; Charbonneau, Hubert; Légaré, Jacques; Miura, Teiji

We investigated population-based vital records of the seventeenth and eighteenth century French Canadian population to assess the effects of marriage season on the outcome of the first births under natural fertility conditions (n=21,698 marriages). Promptness of the first successful conception after marriage differed according to marriage season; the proportion of marriages with a marriage-first birth interval of 8.0-10.0 months was lowest (34%) for marriages in August-October (P=0.001). Although the male/female sex ratio of the babies born with an interval of 8.0-10.0 months was generally higher (1.10) than those with an interval of 10.0-24.0 months (1.05), the marriages in August-October resulted in a significantly reduced sex ratio (0.96) among only the prompt conceptions (P=0.026). We discuss whether this seasonal reduction of the sex ratio could be partly explained by a clustered pregnancy loss of male zygotes in early pregnancy.

Effect of Corticosterone and Hen Body Mass on Primary Sex Ratio in Laying Hen (Gallusgallus), Using Unincubated Eggs1

NARCIS (Netherlands)

Aslam, M.A.; Groothuis, T.G.G.; Smits, M.A.; Woelders, H.

2014-01-01

In various studies, chronic elevation of corticosterone levels in female birds under natural or experimental conditions resulted in female biased offspring sex ratios. In chicken, one study with injected corticosterone resulted in a male sex ratio bias. In the current study, we chronically elevated

Effect of corticosterone and hen body mass on primary sex ratio in laying hen (Gallus gallus), using unincubated eggs

NARCIS (Netherlands)

Aslam, Muhammad Aamir; Groothuis, Ton G. G.; Smits, Mari A.; Woelders, Henri

In various studies, chronic elevation of corticosterone levels in female birds under natural or experimental conditions resulted in female biased offspring sex ratios. In chicken, one study with injected corticosterone resulted in a male sex ratio bias. In the current study, we chronically elevated

Postzygotic incompatibilities between the pupfishes, Cyprinodon elegans and Cyprinodon variegatus: hybrid male sterility and sex ratio bias.

Science.gov (United States)

Tech, C

2006-11-01

I examined the intrinsic postzygotic incompatibilities between two pupfishes, Cyprinodon elegans and Cyprinodon variegatus. Laboratory hybridization experiments revealed evidence of strong postzygotic isolation. Male hybrids have very low fertility, and the survival of backcrosses into C. elegans was substantially reduced. In addition, several crosses produced female-biased sex ratios. Crosses involving C. elegans females and C. variegatus males produced only females, and in backcrosses involving hybrid females and C. elegans males, males made up approximately 25% of the offspring. All other crosses produced approximately 50% males. These sex ratios could be explained by genetic incompatibilities that occur, at least in part, on sex chromosomes. Thus, these results provide strong albeit indirect evidence that pupfish have XY chromosomal sex determination. The results of this study provide insight on the evolution of reproductive isolating mechanisms, particularly the role of Haldane's rule and the 'faster-male' theory in taxa lacking well-differentiated sex chromosomes.

Secondary sex ratio in relation to exposures to polychlorinated biphenyls, dichlorodiphenyl dichloroethylene and methylmercury

DEFF Research Database (Denmark)

Timmermann, Clara Amalie Gade; Choi, Anna L.; Petersen, Maria Skaalum

2017-01-01

This study was undertaken to assess the potential impact of maternal exposures to polychlorinated biphenyl (PCB), dichlorodiphenyl dichloroethylene (DDE) and methylmercury on the secondary sex ratios (the ratio of male to female live births) over a span of 23 years. The study includes prospective...... data from three Faroese birth cohorts, with a total of 2,152 healthy mother-child dyads recruited between 1986 and 2009. The Faroe Islands is a subarctic fishing community, where pilot whale meat and blubber are part of the traditional marine diet. Exposures were measured in maternal hair, serum...... or umbilical cord blood. Confounder adjusted logistic regression models were used to assess the associations between maternal exposures and the secondary sex ratio. A doubling in ΣPCB, p,p'-DDE and mercury concentrations were associated with increased odds by 8% (95% CI = 0-16%), 7% (95% CI = 0-14%) and 9% (95...

Induction of inherited sterility and sex ratio distribution due to exposure to substerilising doses of gamma radiation in cotton bollworm Earias vittella fabricius

International Nuclear Information System (INIS)

Tamhankar, A.J.; Shantharam, K.

2005-01-01

Substerilising doses of gamma radiation induced inherited sterility and sex ratio distortion in the cotton bollworm Earias vittella fabricius. Adults irradiated with 75 Gy and self-crossed, provided sterile F 1 adults, suitable for direct use in sterile insect technique (SIT). In case of 50 Gy, the F 1 adults, when backcrossed, produced F 2 progeny with sex ratio in favour of females (1: >3). With 25 Gy, a sex ratio distortion was recorded in F 1 (1 male: 2.25 females) and self-crossing of F 1 resulted in progeny with a sex ratio of 3:1. Backcrossing of the F 1 female produced F 2 progeny with a sex ratio of 1:5. These results have implications in improving cost/benefit ratio of SIT for this species. (author)

Sex-ratio biasing towards daughters among lower-ranking co-wives in Rwanda

NARCIS (Netherlands)

Pollet, Thomas V.; Fawcett, Tim W.; Buunk, Abraham P.; Nettle, Daniel

2009-01-01

There is considerable debate as to whether human females bias the sex ratio of their offspring as a function of their own condition. We apply the Trivers-Willard prediction-that mothers in poor condition will overproduce daughters-to a novel measure of condition, namely wife rank within a polygynous

Sex Determination, Sex Ratios, and Genetic Conflict

NARCIS (Netherlands)

Werren, John H.; Beukeboom, Leo W.

1998-01-01

Genetic mechanisms of sex determination are unexpectedly diverse and change rapidly during evolution. We review the role of genetic conflict as the driving force behind this diversity and turnover. Genetic conflict occurs when different components of a genetic system are subject to selection in

Sex-Ratio and Gender Differences in Depression in an Unselected Adult Population.

Science.gov (United States)

Baumgart, E. P.; Oliver, J. M.

1981-01-01

Neither sex-ratio nor gender differences in depression were found in adult sample, similar to pattern found among university students. No demographic variable was correlated significantly with depression. Suggests results may be due to the elimination of face-to-face interviews, which expose males to greater negative repercussions for exhibiting…

Comparative AFLP reveals paternal sex ratio chromosome specific DNA sequences in the parasitoid wasp Trichogramma kaykai

NARCIS (Netherlands)

Vugt, van J.J.F.A.; Hulst, van der R.G.M.; Pruijssers, A.; Verbaarschot, P.G.H.; Stouthamer, R.; Jong, de H.

2009-01-01

The parasitoid wasp Trichogramma kaykai with a haplo-diploid sex determination has a B chromosome called the paternal sex ratio (PSR) chromosome that confers paternal genome loss during early embryogenesis, resulting in male offspring. So far, it is not well known whether the PSR chromosome has

Common vole (Microtus arvalis) population sex ratio: biases and process variation

Czech Academy of Sciences Publication Activity Database

Bryja, Josef; Nesvadbová, Jiřina; Heroldová, Marta; Jánová, Eva; Losík, J.; Trebatická, L.; Tkadlec, Emil

2005-01-01

Roč. 83, č. 11 (2005), s. 1391-1399 ISSN 0008-4301 R&D Projects: GA ČR(CZ) GA524/01/1316; GA ČR(CZ) GP206/02/P068; GA ČR(CZ) GA206/04/2003 Institutional research plan: CEZ:AV0Z60930519 Keywords : common vole * population sex ratio Subject RIV: EH - Ecology, Behaviour Impact factor: 1.175, year: 2005

Sex and dark times' strategy: The Dark Triad and time perspective.

Science.gov (United States)

Moraga, Fernando R G; Nima, Ali A; Garcia, Danilo

2017-03-01

We investigated the effect of sex on associations between dark traits and time perspective dimensions. Responses by participants (N = 338) to the Short Dark Triad Inventory and the Zimbardo Time Perspective Inventory showed that while sex was involved in different time perspective associations of Machiavellianism, psychopathy, and narcissism, it did not moderate the dark times' strategy. © 2017 The Institute of Psychology, Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

The paternal-sex-ratio (PSR) chromosome in natural populations of Nasonia (Hymenoptera Chalcidoidea)

NARCIS (Netherlands)

Beukeboom, L.W.; Werren, J.H.

2000-01-01

Selfish genetic elements may be important in promoting evolutionary change. Paternal sex ratio (PSR) is a selfish B chromosome that causes all-male families in the haplodiploid parasitic wasp Nasonia vitripennis, by inducing paternal genome loss in fertilized eggs. The natural distribution and

Second to fourth digit ratio (2D:4D and concentrations of circulating sex hormones in adulthood

Directory of Open Access Journals (Sweden)

Morris Howard A

2011-04-01

Full Text Available Abstract Background The second to fourth digit ratio (2D:4D is used as a marker of prenatal sex hormone exposure. The objective of this study was to examine whether circulating concentrations of sex hormones and SHBG measured in adulthood was associated with 2D:4D. Methods This analysis was based on a random sample from the Melbourne Collaborative Cohort Study. The sample consisted of of 1036 men and 620 post-menopausal women aged between 39 and 70 at the time of blood draw. Concentrations of circulating sex hormones were measured from plasma collected at baseline (1990-1994, while digit length was measured from hand photocopies taken during a recent follow-up (2003-2009. The outcome measures were circulating concentrations of testosterone, oestradiol, dehydroepiandrosterone sulphate, androstenedione, Sex Hormone Binding Globulin, androstenediol glucoronide for men only and oestrone sulphate for women only. Free testosterone and oestradiol were estimated using standard formulae derived empirically. Predicted geometric mean hormone concentrations (for tertiles of 2D:4D and conditional correlation coefficients (for continuous 2D:4D were obtained using mixed effects linear regression models. Results No strong associations were observed between 2D:4D measures and circulating concentrations of hormones for men or women. For males, right 2D:4D was weakly inversely associated with circulating testosterone (predicted geometric mean testosterone was 15.9 and 15.0 nmol/L for the lowest and highest tertiles of male right 2D:4D respectively (P-trend = 0.04. There was a similar weak association between male right 2D:4D and the ratio of testosterone to oestradiol. These associations were not evident in analyses of continuous 2D:4D. Conclusions There were no strong associations between any adult circulating concentration of sex hormone or SHGB and 2D:4D. These results contribute to the growing body of evidence indicating that 2D:4D is unrelated to adult sex

Preconception stress and the secondary sex ratio in a population-based preconception cohort.

Science.gov (United States)

Bae, Jisuk; Lynch, Courtney D; Kim, Sungduk; Sundaram, Rajeshwari; Sapra, Katherine J; Buck Louis, Germaine M

2017-03-01

To examine the association between preconception parental stress and the secondary sex ratio, defined as the ratio of males to females at birth. A population-based preconception cohort. Not applicable. A total of 235 couples who were enrolled before conception in Michigan and Texas between 2005 and 2009 and who had a singleton birth during the follow-up period. Couples were interviewed separately at baseline to obtain information on perceived stress (Cohen's Perceived Stress Scale) and lifetime history of physician-diagnosed anxiety and/or mood disorders. Female partners were also trained to collect basal saliva samples for the measurement of salivary stress markers, alpha-amylase and cortisol. None. Birth outcome data including infant sex were collected upon delivery. Modified Poisson regression models were used to estimate the relative risks (RRs) of a male birth for each stress marker. After adjusting for potential confounders, we observed a 76% increase in the risk of fathering a male infant (RR 1.76; 95% confidence interval 1.17-2.65) in men diagnosed with anxiety disorders compared with those who were not diagnosed. When lifetime history of physician-diagnosed anxiety disorders was modeled jointly for the couple, the association was slightly strengthened (RR 2.03; 95% confidence interval 1.46-2.84). This prospective cohort study suggests that paternal lifetime history of physician-diagnosed anxiety disorders may be associated with an increase in the secondary sex ratio, resulting in an excess of male births. Copyright © 2016 American Society for Reproductive Medicine. All rights reserved.

Mother's prior intrauterine position affects the sex ratio of her offspring in house mice.

OpenAIRE

Vandenbergh, J G; Huggett, C L

1994-01-01

Sex ratio alterations related to environmental factors occur in several mammals, but no mechanism has been identified to explain the adjustment. Intrauterine position (IUP) may provide the context in which such alterations occur. Previous studies on house mice and gerbils reveal that the position of a fetus in the uterus in relation to the sex of its neighbors influences its later anatomy, physiology, and behavior. The anogenital distance (AGD) of females located between two males (2M) is lon...

Sex ratio at birth and racial differences: Why do Black women give ...

African Journals Online (AJOL)

The two important questions that this paper will attempt to answer are: (1) why is it that regardless of race/ethnicity or geographic location, the sex ratio data at birth show more males than females?; and (2) Why is it that regardless of geographic location compared to other racial/ethnic groups, Black women or Women of ...

Establishing sex ratios of sea turtle foraging populations: validation of a novel testosterone hormone assay technology and sex assessment for five species.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Demographic data are essential for developing sound management and conservation plans for marine turtle populations. Sex ratios, even though they are an essential...

Regulation of gonadal sex ratios and pubertal development by the thyroid endocrine system in zebrafish (Danio rerio).

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Sharma, Prakash; Patiño, Reynaldo

2013-04-01

We examined associations between thyroid condition, gonadal sex and pubertal development in zebrafish. Seventy-two-hour postfertilization larvae were reared in untreated medium or in the presence of goitrogens (sodium perchlorate, 0.82 mM; methimazole, 0.15 and 0.3 mM) or thyroxine (1 and 10 nM) for 30 days. Thyrocyte height, gonadal sex and gonadal development were histologically determined at 45 and 60 days postfertilization (dpf). Thyrocyte hypertrophy, an index of hypothyroidism, was observed at 45 and 60 dpf in perchlorate-treated but only at 45 dpf in methimazole-treated fish. Similarly, gonadal sex ratios were biased toward ovaries relative to control animals at 45 and 60 dpf in perchlorate-treated fish but only at 45 dpf in methimazole-treated fish. Gonadal sex ratios were biased toward testes at 45 and 60 dpf in thyroxine-treated fish. Spermatogenesis was delayed in testes from goitrogen-treated fish at 60 dpf relative to control values, but was unaffected in testes from thyroxine-treated individuals. Oogenesis seemed to be nonspecifically delayed in all treatments relative to control at 60 dpf. This study confirmed the previously reported association between hypothyroid condition and ovarian-skewed ratios, and hyperthyroid condition and testicular-skewed ratios, and also showed that male pubertal development is specifically delayed by experimental hypothyroidism. The simultaneous recovery from the hypothyroid and ovary-inducing effects of methimazole by 60 dpf (27 days post-treatment) suggests that the ovary-skewing effect of goitrogens is reversible when thyroid conditions return to basal levels before developmental commitment of gonadal sex. Conversely, the masculinizing effect of hyperthyroidism seems to be stable and perhaps permanent. Published by Elsevier Inc.

Regulation of gonadal sex ratios and pubertal development by the thyroid endocrine system in zebrafish (Danio rerio)

Science.gov (United States)

Sharma, Prakash; Patino, Reynaldo

2013-01-01

We examined associations between thyroid condition, gonadal sex and pubertal development in zebrafish. Seventy-two-hour postfertilization larvae were reared in untreated medium or in the presence of goitrogens (sodium perchlorate, 0.82 mM; methimazole, 0.15 and 0.3 mM) or thyroxine (1 and 10 nM) for 30 days. Thyrocyte height, gonadal sex and gonadal development were histologically determined at 45 and 60 days postfertilization (dpf). Thyrocyte hypertrophy, an index of hypothyroidism, was observed at 45 and 60 dpf in perchlorate-treated but only at 45 dpf in methimazole-treated fish. Similarly, gonadal sex ratios were biased toward ovaries relative to control animals at 45 and 60 dpf in perchlorate-treated fish but only at 45 dpf in methimazole-treated fish. Gonadal sex ratios were biased toward testes at 45 and 60 dpf in thyroxine-treated fish. Spermatogenesis was delayed in testes from goitrogen-treated fish at 60 dpf relative to control values, but was unaffected in testes from thyroxine-treated individuals. Oogenesis seemed to be nonspecifically delayed in all treatments relative to control at 60 dpf. This study confirmed the previously reported association between hypothyroid condition and ovarian-skewed ratios, and hyperthyroid condition and testicular-skewed ratios, and also showed that male pubertal development is specifically delayed by experimental hypothyroidism. The simultaneous recovery from the hypothyroid and ovary-inducing effects of methimazole by 60 dpf (27 days post-treatment) suggests that the ovary-skewing effect of goitrogens is reversible when thyroid conditions return to basal levels before developmental commitment of gonadal sex. Conversely, the masculinizing effect of hyperthyroidism seems to be stable and perhaps permanent.

Effects of gamma radiation on development, sterility, fecundity, and sex ratio of Dermanyssus gallinae (DeGeer) (Acari: Dermanyssidae)

International Nuclear Information System (INIS)

Entrekin, D.L.; Oliver, J.H. Jr.; Pound, J.M.

1987-01-01

Protonymphal Dermanyssus gallinae were irradiated with 0.50, 0.75, 1.0, 3.0, and 6.0 krad of gamma radiation and subsequently monitored regarding their developmental, feeding, and mating success. Also, sex ratios of adults treated as protonymphs were recorded as were sex ratios of embryos and F1 adults produced by these adults. Doses up to 1.0 krad did not prevent development of treated protonymphs to the adult stage or stop mating. Three krad reduced the number of treated protonymphs attaining adulthood and 6.0-krad treatment prevented all mites from developing to the adult stage. Egg (embryo) production was normal for mites treated with 0.50 krad, but significantly curtailed by doses of 0.75 krad and greater. Radiation doses used in this study did not appear to affect the normal variable sex ratios observed in untreated mites

Economics, cultural transmission, and the dynamics of the sex ratio at birth in China.

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Lipatov, Mikhail; Li, Shuzhuo; Feldman, Marcus W

2008-12-09

In rural China, the ratio of newborn boys to newborn girls [sex ratio at birth (SRB)] has been rising for several decades, to values significantly above its biological norm. This trend has a number of alarming societal consequences, and has attracted the attention of scholars and politicians. The root of the problem lies in a 2,500-year-old culture of son preference. This culture is intricately linked with the economic reality of each couple's life, so that there are financial and psychological repercussions to parents who have no sons. To bring greater clarity and understanding to this issue, we present a quantitative framework that describes the interaction between economics and cultural transmission. We start with an explicit mechanism by which economic incentives can change cultural beliefs of a given individual, and go on to include a mechanism of cultural inheritance from generation to generation. We then show how economic conditions can affect the dynamics of cultural change in an entire society, and may lead to a decrease in the country's sex ratio at birth.

[Sex ratio and environmental influence on population growth rate of Callinectes bellicosus (Decapoda: Portunidae) in the Gulf of California].

Science.gov (United States)

Rodríguez-Félix, Demetrio; Cisneros-Mata, Miguel Angel; Aragón-Noriega, Eugenio Alberto; Arreola-Lizárraga, José Alfredo

2016-09-01

The brown swimming crab (Callinectes bellicosus) is an economically important species in the Gulf of California, and its fishing activity, held in Sonora from 1986, has been affected by a 20-year declining trend in its biomass. With the aim to understand the possible reasons of this species population changes along time, we estimated population growth rate (r) and sex ratio of C. bellicosus, and combined them with three parameters describing its habitat: sea temperature, wetland extension and habitat size in four areas along the coast of Sonora. For this, monthly mean sex ratio was estimated from crabs samples obtained from commercial catches during 1998-2002 and 2012; mean sea surface temperature for the spawning period (May-August) were derived from remote sensors for the same years; while wetland coverages were obtained from published reports, and habitat size was estimated as the fishing surface. For each area, r was estimated using a method developed for limited data situations using commercial landings (t) from 1986-2013. With data from the four areas, simple and multiple linear regression models were developed to ascertain theoretical sensitivities of r to variations in sex ratio and environmental parameters. A total of 24 556 crabs were sampled; males dominated (68.8 %) over females during the study period and in all areas; a cluster analysis identified two groups according to sex ratio: a Northern group with zones 1 and 2, and a Southern group with zones 3 and 4. r values were different in all zones (P0.995). Both the estimated data and sensitivity analyses suggest the existence of a direct and positive dependence of r on the proportion of female crabs and wetland size. We hypothesize that excess fishing of females caused the declining biomass trend of the brown swimming crab in Sonora, and concluded on the convenience of implementing harvest refugia inside coastal wetlands to protect females during the spawning season.

Sex Ratios, Economic Power, and Women's Roles: A Theoretical Extension and Empirical Test.

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South, Scott J.

1988-01-01

Tested hypotheses concerning sex ratios, women's roles, and economic power with data from 111 countries. Found undersupply of women positively associated with proportion of women who marry and fertility rate; inversely associated with women's average age at marriage, literacy rate, and divorce rate. Suggests women's economic power may counteract…

Mixture Analysis and Mammalian Sex Ratio Among Middle Pleistocene Mouflon of Arago Cave, France

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Monchot, Hervé

1999-09-01

In archaeological studies, it is often important to be able assess sexual dimorphism and sex ratios in populations. Obtaining sex ratio is easy if each individual in the population can be accurately sexed through the use of one more objective variables. But this is often impossible, due to incompleteness of the osteological record. A modern statistical approach to handle this problem is Mixture Analysis using the method of maximum likelihood. It consists of determining how many groups are present in the sample, two in this case, in which proportions they occur, and to estimate the parameters accordingly. This paper shows the use of this method on vertebrate fossil populations in a prehistoric context with implications on prey acquisition by early humans. For instance, the analysis of mouflon bones from Arago cave (Tautavel, France) indicates that there are more females than males in the F layer. According to the ethology of the animal, this indicates that the hunting strategy could be the result of selective choice of the prey. Moreover, we may deduce the presence of Anteneandertalians on the site during spring and summer periods.

Auger electron spectroscopy for the determination of sex and age related Ca/P ratio at different bone sites

International Nuclear Information System (INIS)

Balatsoukas, Ioannis; Kourkoumelis, Nikolaos; Tzaphlidou, Margaret

2010-01-01

The Ca/P ratio of normal cortical and trabecular rat bone was measured by Auger electron spectroscopy (AES). Semiquantitative analysis was carried out using ratio techniques to draw conclusions on how age, sex and bone site affect the relative composition of calcium and phosphorus. Results show that Ca/P ratio is not sex dependent; quite the opposite, bone sites exhibit variations in elemental stoichiometry where femoral sections demonstrate higher Ca/P ratio than rear and front tibias. Age-related changes are more distinct for cortical bone in comparison with the trabecular bone. The latter's Ca/P ratio remains unaffected from all the parameters under study. This study confirms that AES is able to successfully quantify bone mineral main elements when certain critical points, related to the experimental conditions, are addressed effectively.

Effect of time of artificial insemination on embryo sex ratio in dairy cattle

NARCIS (Netherlands)

Roelofs, J.B.; Bouwman, E.B.; Pedersen, H.G.; Riestra Rasmussen, Z.; Soede, N.M.; Thomsen, P.D.; Kemp, B.

2006-01-01

The objective of the present study was to examine whether different intervals between insemination and ovulation have an influence on the sex of seven-day-old embryos in dairy cattle. Cows were inseminated once with semen of one of two bulls of proven fertility between 36 h before ovulation and 12 h

Resource Elasticity of Offspring Survival and the Optimal Evolution of Sex Ratios

Science.gov (United States)

Wang, Rui-Wu; Wang, Ya-Qiang; He, Jun-Zhou; Li, Yao-Tang

2013-01-01

The fitness of any organisms includes the survival and reproductive rate of adults and the survival of their offspring. Environmental selection pressures might not affect these two aspects of an organism equally. Assuming that an organism first allocates its limited resources to maintain its survival under environmental selection pressure, our model, based on the evolutionarily stable strategy theory, surprisingly shows that the sex ratio is greatly affected by the environmental pressure intensity and by the reproductive resource elasticity of offspring survival. Moreover, the concept of the resource elasticity of offspring survival intrinsically integrates the ecological concepts of K selection and r selection. The model shows that in a species with reproductive strategy K, increased environmental selection pressure will reduce resource allocation to the male function. By contrast, in a species with reproductive strategy r, harsher environmental selection pressure will increase allocation to the male function. The elasticity of offspring survival might vary not only across species, but also across many other factors affecting the same species (e.g., age structure, spatial heterogeneity), which explains sex ratio differences across species or age structures and spatial heterogeneity in the same species. PMID:23468826

First Assessment of the Sex Ratio for an East Pacific Green Sea Turtle Foraging Aggregation: Validation and Application of a Testosterone ELISA.

Directory of Open Access Journals (Sweden)

Camryn D Allen

Full Text Available Determining sex ratios of endangered populations is important for wildlife management, particularly species subject to sex-specific threats or that exhibit temperature-dependent sex determination. Sea turtle sex is determined by incubation temperature and individuals lack external sex-based traits until sexual maturity. Previous research utilized serum/plasma testosterone radioimmunoassays (RIA to determine sex in immature/juvenile sea turtles. However, there has been a growing application of enzyme-linked immunosorbent assay (ELISA for wildlife endocrinology studies, but no study on sea turtles has compared the results of ELISA and RIA. This study provides the first sex ratio for a threatened East Pacific green sea turtle (Chelonia mydas foraging aggregation, a critical step for future management of this species. Here, we validate a testosterone ELISA and compare results between RIA and ELISA of duplicate samples. The ELISA demonstrated excellent correspondence with the RIA for providing testosterone concentrations for sex determination. Neither assay proved reliable for predicting the sex of reproductively active females with increased testosterone production. We then applied ELISA to examine the sex ratio of 69 green turtles foraging in San Diego Bay, California. Of 45 immature turtles sampled, sex could not be determined for three turtles because testosterone concentrations fell between the ranges for either sex (females: 4.1-113.1 pg/mL, males: 198.4-2,613.0 pg/mL and these turtles were not subsequently recaptured to enable sex determination; using a Bayesian model to predict probabilities of turtle sex we predicted all three 'unknowns' were female (> 0.86. Additionally, the model assigned all turtles with their correct sex (if determined at recapture with 100% accuracy. Results indicated a female bias (2.83F:1M among all turtles in the aggregation; when focusing only on putative immature turtles the sex ratio was 3.5F:1M. With appropriate

Haldane’s Rule Is Linked to Extraordinary Sex Ratios and Sperm Length in Stalk-Eyed Flies

Science.gov (United States)

Wilkinson, Gerald S.; Christianson, Sarah J.; Brand, Cara L.; Ru, George; Shell, Wyatt

2014-01-01

We use three allopatric populations of the stalk-eyed fly Teleopsis dalmanni from Southeast Asia to test two predictions made by the sex chromosome drive hypothesis for Haldane’s rule. The first is that modifiers that suppress or enhance drive should evolve rapidly and independently in isolated populations. The second is that drive loci or modifiers should also cause sterility in hybrid males. We tested these predictions by assaying the fertility of 2066 males derived from backcross experiments involving two pairs of populations and found that the proportion of mated males that fail to produce any offspring ranged from 38 to 60% among crosses with some males producing strongly female-biased or male-biased sex ratios. After genotyping each male at 25–28 genetic markers we found quantitative trait loci (QTL) that jointly influence male sterility, sperm length, and biased progeny sex ratios in each pair of populations, but almost no shared QTL between population crosses. We also discovered that the extant XSR chromosome has no effect on sex ratio or sterility in these backcross males. Whether shared QTL are caused by linkage or pleiotropy requires additional study. Nevertheless, these results indicate the presence of a “cryptic” drive system that is currently masked by suppressing elements that are associated with sterility and sperm length within but not between populations and, therefore, must have evolved since the populations became isolated, i.e., in hybrid sterility. PMID:25164880

Phenotypic plasticity in response to the social environment: effects of density and sex ratio on mating behaviour following ecotype divergence.

Directory of Open Access Journals (Sweden)

Kristina Karlsson

Full Text Available The ability to express phenotypically plastic responses to environmental cues might be adaptive in changing environments. We studied phenotypic plasticity in mating behaviour as a response to population density and adult sex ratio in a freshwater isopod (Asellus aquaticus. A. aquaticus has recently diverged into two distinct ecotypes, inhabiting different lake habitats (reed Phragmites australis and stonewort Chara tomentosa, respectively. In field surveys, we found that these habitats differ markedly in isopod population densities and adult sex ratios. These spatially and temporally demographic differences are likely to affect mating behaviour. We performed behavioural experiments using animals from both the ancestral ecotype ("reed" isopods and from the novel ecotype ("stonewort" isopods population. We found that neither ecotype adjusted their behaviour in response to population density. However, the reed ecotype had a higher intrinsic mating propensity across densities. In contrast to the effects of density, we found ecotype differences in plasticity in response to sex ratio. The stonewort ecotype show pronounced phenotypic plasticity in mating propensity to adult sex ratio, whereas the reed ecotype showed a more canalised behaviour with respect to this demographic factor. We suggest that the lower overall mating propensity and the phenotypic plasticity in response to sex ratio have evolved in the novel stonewort ecotype following invasion of the novel habitat. Plasticity in mating behaviour may in turn have effects on the direction and intensity of sexual selection in the stonewort habitat, which may fuel further ecotype divergence.

Live birth sex ratio after in vitro fertilization and embryo transfer in China--an analysis of 121,247 babies from 18 centers.

Science.gov (United States)

Bu, Zhiqin; Chen, Zi-Jiang; Huang, Guoning; Zhang, Hanwang; Wu, Qiongfang; Ma, Yanping; Shi, Juanzi; Xu, Yanwen; Zhang, Songying; Zhang, Cuilian; Zhao, Xiaoming; Zhang, Bo; Huang, Yuanhua; Sun, Zhengyi; Kang, Yuefan; Wu, Riran; Wu, Xueqing; Sun, Haixiang; Sun, Yingpu

2014-01-01

In order to study the impact of procedures of IVF/ICSI technology on sex ratio in China, we conducted this multi-center retrospective study including 121,247 babies born to 93,895 women in China. There were 62,700 male babies and 58,477 female babies, making the sex ratio being 51.8% (Male: Female  = 107:100). In univariate logistic regression analysis, sex ratio was imbalance toward females of 50.3% when ICSI was preformed compared to 47.7% when IVF was used (Pratio in IVF/ICSI babies was significantly higher toward males in transfers of blastocyst (54.9%) and thawed embryo (52.4%) when compared with transfers of cleavage stage embryo (51.4%) and fresh embryo (51.5%), respectively. Multiple delivery was not associated with sex ratio. However, in multivariable logistic regression analysis after controlling for related factors, only ICSI (adjusted OR =  .90, 95%CI: 0.88-0.93; Pratio in IVF/ICSI babies. In conclusion, the live birth sex ratio in IVF/ICSI babies was influenced by the use of ICSI, which may decrease the percentage of male offspring, or the use of blastocyst transfer, which may increase the percentage of male offspring.

Mating Frequency and Effects on Sex Ratio in Female Parasitoids of xanthopimpla Stemmator (Thunberg). Implications in biological control Programmes

International Nuclear Information System (INIS)

Gitau, C.W.

2002-01-01

Cereals, especially maize and sorghum are the most important field crops in Africa. classical biological Control is a management strategy that employs natural enemies against exotic pests on cereal crops. The method has been used against Chilo partellus (Swinhoe) (Lepidoptera: Crambidae), an introduced pest of maize, using the larval parasitoid cotesia flavipes (Cameron). However, C. flavipes is not able to attack all stem borer species in targeted areas. to complement its work, Xanthopimpla stemmator has successfully been established in Mauritius on Chilo sacchariphagus (Bojer). It is a common phenomenon for haplo-diploid parasitoids to give rise to male progeny when insemination does not take place. Mating becomes important to the parasitoid population since a male biased sex ratio can bring about collapse of the population. The aim of this study was to determine wether xanthopimpla stemmator females mat more than once and wether sex ratio of progeny is affected by multiple mating in female X. stemmator. The female showed a tendency to mate once. Multiple mating did not have any significant effect on either sex ratio or longevity. More males were produced in multiple mated females than once mated females.The effect of multiple mating in X. stemmator on sex ratio in relation to biocontrol programmes are discussed

Further observations on sex ratio among infants born to survivors of the atomic bombs, Hiroshima and Nagasaki

Energy Technology Data Exchange (ETDEWEB)

Schull, W J; Neel, J V; Hashizume, Asaji

1965-11-18

Data are presented on the sex ratio of 47,624 children born in Hiroshima and Nagasaki during 1956 to 1962. The total number of births in these two cities for which information is available is now 140,542, and of this number in 73,994 instances one or both parents were exposed to the atomic bombs. The suggestion of an effect of exposure on sex ratio in the earlier data is not borne out by the present findings. One can argue either that a small early effect has disappeared or that the original observation had no biological significance. 27 references, 4 tables.

Offspring sex ratios in relation to mutual ornamentation and extra-pair paternity in the Black Swan Cygnus atratus

NARCIS (Netherlands)

Kraaijeveld, Ken; Ming, Ma; Komdeur, Jan; Mulder, Raoul A.

In sexually dichromatic birds, females may adaptively adjust the sex ratio of their offspring prior to hatching in relation to male ornamentation, for example, by producing more sons when paired to a highly attractive partner. However, to our knowledge no studies have investigated offspring sex

Calcium availability influences litter size and sex ratio in white-footed mice (Peromyscus leucopus.

Directory of Open Access Journals (Sweden)

Christina M Schmidt

Full Text Available The production of offspring typically requires investment of resources derived from both the environment and maternal somatic reserves. As such, the availability of either of these types of resources has the potential to limit the degree to which resources are allocated to reproduction. Theory and empirical studies have argued that mothers modify reproductive performance relative to exogenous resource availability and maternal condition by adjusting size, number or sex of offspring produced. These relationships have classically been defined relative to availability of energy sources; however, in vertebrates, calcium also plays a critical role in offspring production, as a considerable amount of calcium is required to support the development of offspring skeleton(s. We tested whether the availability of calcium influences reproductive output by providing female white-footed mice with a low-calcium or standard diet from reproductive maturity to senescence. We then compared maternal skeletal condition and reproductive output, based on offspring mass, offspring number and litter sex ratio, between dietary treatments. Mothers on the low-calcium diet exhibited diminished skeletal condition at senescence and produced smaller and strongly female-biased litters. We show that skeletal condition and calcium intake can influence sex ratio and reproductive output following general theoretical models of resource partitioning during reproduction.

Genetically significant dose and sex ratio of the offsprings of patient treated with 131I for hyperthyroidism

International Nuclear Information System (INIS)

Takeshita, Akihisa

1975-01-01

The gonadal doses following the 131 I treatment of 6 male and 14 female patients with hyperthyroidism were calculated by the method of MIRD, measuring daily radioactivity in the thyroid gland and circulating blood. The testicular dose was 0.52 +- 0.256 rads and the ovarian dose was 0.632 +- 0.488 rads per mCi. In 1965, the genetically significant dose from 131 I treatment of 925 patients with hyperthyroidism was estimated to be 0.0136 mrads/person/year. The genetically significant dose would amount to 0.0613 mrads/person/year, assuming that the total amount of 131 I supplied for treatment in 1965 was administered to treat the hyperthyroid patients with an age-and sex distribution similar to that of the above mentioned group of patients. Sex ratios of the offspring of male and female patients treated with 131 I from 1953 to 1966 were compared with those of offspring born to male and female patients before the treatment. The proportion of males was higher among the offspring of male patients after 131 I treatment than among the offspring of the controls, but the difference was not statistically significant. The sex ratio of the offspring of female patients was not different from that of controls. The mean age of the parents at the times of their children's birth after 131 I treatment was 2.6 - 6.0 year older in male patients and 2.8 - 2.9 year older in female patients than that of controls. (J.P.N.)

Sex pheromone component ratios and mating isolation among three Lygus plant bug species of North America

Science.gov (United States)

Byers, John A.; Fefer, Daniela; Levi-Zada, Anat

2013-12-01

The plant bugs Lygus hesperus, Lygus lineolaris, and Lygus elisus (Hemiptera: Miridae) are major pests of many agricultural crops in North America. Previous studies suggested that females release a sex pheromone attractive to males. Other studies showed that males and females contain microgram amounts of ( E)-4-oxo-2-hexenal, hexyl butyrate, and ( E)-2-hexenyl butyrate that are emitted as a defense against predators. Using gas chromatography-mass spectrometry, we found that female L. lineolaris and L. elisus have a 4:10 ratio of hexyl butyrate to ( E)-2-hexenyl butyrate that is reversed from the 10:1 ratio in female L. hesperus (males of the three species have ~10:1 ratio). These reversed ratios among females of the species suggest a behavioral role. Because both sexes have nearly equal amounts of the major volatiles, females should release more to attract males. This expectation was supported because L. hesperus females released more hexyl butyrate (mean of 86 ng/h) during the night (1800-0700 hours) than did males (pheromone component for all three species, ( E)-2-hexenyl butyrate is essential for L. elisus and L. lineolaris, and hexyl butyrate is essential for L. hesperus. However, all three components are recognized by each species since ratios of the butyrate esters are critical for conspecific attraction and heterospecific avoidance by males and thus play a role in reproductive isolation among the three species. Because L. hesperus males and females are known to emit these major volatiles for repelling ant predators, our study links defensive allomones in Lygus bugs with an additional use as sex pheromones.

Analysis of case-parent trios for imprinting effect using a loglinear model with adjustment for sex-of-parent-specific transmission ratio distortion

DEFF Research Database (Denmark)

Huang, Lam Opal; Infante-Rivard, Claire; Labbe, Aurélie

2017-01-01

Transmission ratio distortion (TRD) is a phenomenon where parental transmission of disease allele to the child does not follow the Mendelian inheritance ratio. TRD occurs in a sex-of-parent-specific or non-sex-of-parent-specific manner. An offset computed from the transmission probability of the ...

Cognitive ability correlates positively with son birth and predicts cross-cultural variation of the offspring sex ratio

Science.gov (United States)

Dama, Madhukar Shivajirao

2013-06-01

Human populations show remarkable variation in the sex ratio at birth which is believed to be related to the parental condition. In the present study, the global variation of sex ratio at birth (SRB, proportion of male offspring born) was analyzed with respect to indirect measure of condition, the intelligence quotient (IQ). IQ correlates strongly with lifespan across nations, which makes it a good indicator of health of the large populations. Relation between three standard measures of average national IQ and SRB was studied using multiple linear regression models. Average national IQ was positively correlated with SRB ( r = 0.54 to 0.57, p difference in general condition of populations.

Temporal patterns in capture rate and sex ratio of forest bats in Arkansas

Science.gov (United States)

Roger W. Perry; S. Andrew Carter; Ronald E. Thill

2010-01-01

We quantified changes in capture rates and sex ratios from May to Sept. for eight species of bats, derived from 8 y of extensive mist netting in forests of the Ouachita Mountains, Arkansas. Our primary goal was to determine patterns of relative abundance for each species of bat captured over forest streams and to determine if these patterns were similar to patterns of...

Normal Female Germ Cell Differentiation Requires the Female X Chromosome to Autosome Ratio and Expression of Sex-Lethal in DROSOPHILA MELANOGASTER

OpenAIRE

Schüpbach, Trudi

1985-01-01

In somatic cells of Drosophila, the ratio of X chromosomes to autosomes (X:A ratio) determines sex and dosage compensation. The present paper addresses the question of whether germ cells also use the X:A ratio for sex determination and dosage compensation. Triploid female embryos were generated which, through the loss of an unstable ring-X chromosome, contained some germ cells of 2X;3A constitution in their ovaries. Such germ cells were shown to differentiate along one of two alternative pat...

The Effects of Sex-Ratio and Density on Locomotor Activity in the House Fly, Musca domestica

Science.gov (United States)

Bahrndorff, Simon; Kjærsgaard, Anders; Pertoldi, Cino; Loeschcke, Volker; Schou, Toke M.; Skovgård, Henrik; Hald, Birthe

2012-01-01

Although locomotor activity is involved in almost all behavioral traits, there is a lack of knowledge on what factors affect it. This study examined the effects of sex—ratio and density on the circadian rhythm of locomotor activity of adult Musca domestica L. (Diptera: Muscidae) using an infra—red light system. Sex—ratio significantly affected locomotor activity, increasing with the percentage of males in the vials. In accordance with other studies, males were more active than females, but the circadian rhythm of the two sexes was not constant over time and changed during the light period. There was also an effect of density on locomotor activity, where males at intermediate densities showed higher activity. Further, the predictability of the locomotor activity, estimated as the degree of autocorrelation of the activity data, increased with the number of males present in the vials both with and without the presence of females. Overall, this study demonstrates that locomotor activity in M. domestica is affected by sex—ratio and density. Furthermore, the predictability of locomotor activity is affected by both sex—ratio, density, and circadian rhythm. These results add to our understanding of the behavioral interactions between houseflies and highlight the importance of these factors when designing behavioral experiments using M. domestica.

Maternal fructose and/or salt intake and reproductive outcome in the rat: effects on growth, fertility, sex ratio, and birth order.

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Gray, Clint; Long, Sophie; Green, Charlotte; Gardiner, Sheila M; Craigon, Jim; Gardner, David S

2013-09-01

Maternal diet can significantly skew the secondary sex ratio away from the expected value of 0.5 (proportion males), but the details of how diet may do this are unclear. Here, we altered dietary levels of salt (4% salt in the feed) and/or fructose (10% in the drinking water) of pregnant rats to model potential effects that consumption of a "Western diet" might have on maternofetal growth, development, and sex ratio. We demonstrate that excess fructose consumption before and during pregnancy lead to a marked skew in the secondary sex ratio (proportion of males, 0.60; P < 0.006). The effect was not mediated by selective developmental arrest of female embryos or influenced by fetal position in the uterine horn or sex-specific effects on sperm motility, suggesting a direct effect of glycolyzable monosaccharide on the maternal ovary and/or ovulated oocyte. Furthermore, combined excess maternal consumption of salt and fructose-sweetened beverage significantly reduced fertility, reflected as a 50% reduction in preimplantation and term litter size. In addition, we also noted birth order effects in the rat, with sequential implantation sites tending to be occupied by the same sex.

Great tit hatchling sex ratios

NARCIS (Netherlands)

Lessells, C.M.; Mateman, A.C.; Visser, J.

1996-01-01

The sex of Great Tit Parus major nestlings was determined using PCR RAPDs. Because this technique requires minute amounts of DNA, chicks could be sampled soon (0-2d) after hatching, before any nestling mortality occurred. The proportion of males among 752 chicks hatching in 102 broods (98.9% of

Sex ratio variation in the bumblebee Bombus terrestris

DEFF Research Database (Denmark)

Duchateau, Marie José; Velthuis, Hayo H. W.; Boomsma, Jacobus Jan

2004-01-01

Bombus terrestris, bumblebees, colony development, queen control, reproductive strategies, sex allocation......Bombus terrestris, bumblebees, colony development, queen control, reproductive strategies, sex allocation...

Delimitation of the embryonic thermosensitive period for sex determination using an embryo growth model reveals a potential bias for sex ratio prediction in turtles.

Science.gov (United States)

Girondot, Marc; Monsinjon, Jonathan; Guillon, Jean-Michel

2018-04-01

The sexual phenotype of the gonad is dependent on incubation temperature in many turtles, all crocodilians, and some lepidosaurians. At hatching, identification of sexual phenotype is impossible without sacrificing the neonates. For this reason, a general method to infer sexual phenotype from incubation temperatures is needed. Temperature influences sex determination during a specific period of the embryonic development, starting when the gonad begins to form. At constant incubation temperatures, this thermosensitive period for sex determination (TSP) is located at the middle third of incubation duration (MTID). When temperature fluctuates, the position of the thermosensitive period for sex determination can be shifted from the MTID because embryo growth is affected by temperature. A method is proposed to locate the thermosensitive period for sex determination based on modelling the embryo growth, allowing its precise identification from a natural regime of temperatures. Results from natural nests and simulations show that the approximation of the thermosensitive period for sex determination to the middle third of incubation duration may create a quasi-systematic bias to lower temperatures when computing the average incubation temperature during this period and thus a male-bias for sex ratio estimate. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sex preferences among mothers delivering at Patan Hospital.

Science.gov (United States)

Chhetri, U D; Ansari, I; Bandary, S; Adhikari, N

2011-01-01

High sex ratios at birth (SRB) are seen in China, Taiwan, South Korea, parts of India and Vietnam. The imbalance is the result of son preference, accentuated by declining fertility. Prenatal sex determination and female feticides are common in many countries. It is reflected in sex ratio To determine reasons for the preferences for different sex; to find out whether there is altered sex ratio at birth and to find out whether female feticide are common among women who had abortion. It is a prospective study. Women who had previous history of abortion and had delivered at Patan Hospital in the year 2066 were interviewed as per questionnaires. Among 560 women with total live births of 965, (462 male and 503 female) during their life time the overall sex ratio was 92 male per 100 female birth; total abortions were 663. Preferences for male were 10%, female 15.4% and either was for 74%. The reason for male preference was to continue family lineage, to bring honor, old age security, and performing funeral rites while the reasons for daughter preferences were that they understand mothers pain, help in household work. The sex ratio of the babies born during the study period was 113 male per 100 female births. The Sex ratio at birth from 1st to 6th deliveries was 61, 79, 101, 210, 286 and 1100 male per 100 female birth respectively. Prenatal sex selection was 8% (by USG) but none had sex selected abortion. Sex ratio of those delivered during the study period was skewed (136 boys per 100 girls) towards male. There was shift in SRB in 4th and subsequent pregnancies in favor of boys. As the male sex ratio increased the number of induced abortion decreased in subsequent pregnancies.

Testosterone has a long-term effect on primary sex ratio of first eggs in pigeons-in search of a mechanism

NARCIS (Netherlands)

Goerlich, V. C.; Dijkstra, C.; Schaafsma, S. M.; Groothuis, T. G. G.

2009-01-01

Despite accumulating evidence that birds, in which females are the heterogametic sex, are able to manipulate primary offspring sex ratio, the underlying mechanism remains elusive. Steroid hormones. which govern female reproduction and are also accumulated by the developing follicle could potentially

Selective interactions among Rh, ABO, and sex ratio of newborns.

Science.gov (United States)

Valenzuela, C Y; Walton, R

1985-01-01

The hypothesis that the Rh and ABO blood systems behave like the HLA system in relation to mother-conception tolerance-rejection mechanisms was tested in 25,501 mother-infant pairs. According to this hypothesis, heterozygotes carrying a paternal gene that is not present in their mothers should be better tolerated than homozygotes. Significantly more BO infants born to AO mothers. AO infants born to BO mothers, Rh(+) heterozygotes born to Rh(-) mothers, and less significantly AO infants born to OO mothers confirm the hypothesis. Fewer homozygotes occurred in Rh(-) infants born to Rh(+) mothers and in O infants born to non-O mothers. Deviations from the Hardy-Weinberg equilibrium found in the ABO system were modified by the Rh and sex of the infant. These data strongly support the hypothesis that at least two feto-maternal systems influence the destiny of pregnancies: the classical known incompatibility system which operates late in pregnancy and a new one which is based on the induction of maternal tolerance early in pregnancy: maternal tolerance seems to be better elicited by heterozygous eggs or embryos carrying a gene not present in the mother. The data also support the hypothesis that the sex ratio is influenced by feto-maternal tolerance-rejection mechanisms associated with the ABO and Rh systems.

Mapping Causes and Implications of India's Skewed Sex Ratio and Poverty problem using Fuzzy & Neutrosophic Relational Maps

OpenAIRE

Gaurav; Kumar, Megha; Bhutani, Kanika; Aggarwal, Swati

2016-01-01

Numerous studies by different researchers have confirmed that skewed sex ratio is a critical social problem in India. This enduring problem of gender imbalance is the collective result of factors like sex selective abortion, gender discrimination, son preference for the preservation of tribe, emergence of new technologies in medical field and many more factors. Another severe problem to be addressed in India is poverty. Many factors contribute to the perpetuation of poverty such as illiteracy...

The evolution of sex roles in birds is related to adult sex ratio

OpenAIRE

Liker, András; Freckleton, Robert P.; Székely, Tamás

2013-01-01

Sex-role reversal represents a formidable challenge for evolutionary biologists, since it is not clear which ecological, life-history or social factors facilitated conventional sex roles (female care and male-male competition for mates) to be reversed (male care and female-female competition). Classic theories suggested ecological or life-history predictors of role reversal, but most studies failed to support these hypotheses. Recent theory however predicts that sex-role reversal should be dr...

High fat diet prevents over-crowding induced decrease of sex ratio in mice.

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Madhukar Shivajirao Dama

Full Text Available Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to their offspring's future reproductive success. In the present study, we tested the effect of housing mice under crowded condition on the sex ratio and whether the fat content of the diet has any influence on the outcome of pregnancies. Three-week-old mice were placed on the control diet (NFD for 3 weeks. Thereafter the mice were allotted randomly to two groups of 7 cages each with 4, 6, 8, 10, 12, 14, and 16 mice in every cage to create increasing crowding gradient and fed either NFD or high fat diet (HFD. After 4 weeks, dams were bred and outcomes of pregnancy were analyzed. The average dam body weight (DBW at conception, litter size (LS and SR were significantly higher in HFD fed dams. Further, male biased litters declined with increasing crowding in NFD group but not in HFD. The LS and SR in NFD declined significantly with increasing crowding, whereas only LS was reduced in HFD group. We conclude that female mice housed under overcrowding conditions shift offspring SR in favor of daughters in consistent with the TW hypothesis and high fat diet reduces this influence of overcrowding.

Genome-wide association study uncovers a novel QTL allele of AtS40-3 that affects the sex ratio of cyst nematodes in Arabidopsis.

Science.gov (United States)

Anwer, Muhammad Arslan; Anjam, Muhammad Shahzad; Shah, Syed Jehangir; Hasan, M Shamim; Naz, Ali A; Grundler, Florian M W; Siddique, Shahid

2018-03-24

Plant-parasitic cyst nematodes are obligate sedentary parasites that infect the roots of a broad range of host plants. Cyst nematodes are sexually dimorphic, but differentiation into male or female is strongly influenced by interactions with the host environment. Female populations typically predominate under favorable conditions, whereas male populations predominate under adverse conditions. Here, we performed a genome-wide association study (GWAS) in an Arabidopsis diversity panel to identify host loci underlying variation in susceptibility to cyst nematode infection. Three different susceptibility parameters were examined, with the aim of providing insights into the infection process, the number of females and males present in the infected plant, and the female-to-male sex ratio. GWAS results suggested that variation in sex ratio is associated with a novel quantitative trait locus allele on chromosome 4. Subsequent candidate genes and functional analyses revealed that a senescence-associated transcription factor, AtS40-3, and PPR may act in combination to influence nematode sex ratio. A detailed molecular characterization revealed that variation in nematode sex ratio was due to the disturbed common promoter of AtS40-3 and PPR genes. Additionally, single nucleotide polymorphisms in the coding sequence of AtS40-3 might contribute to the natural variation in nematode sex ratio.

Sex ratio of the offspring of Sprague-Dawley rats exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in utero and lactationally in a three-generation study

International Nuclear Information System (INIS)

Rowlands, J.C.; Budinsky, R.A.; Aylward, L.L.; Faqi, A.S.; Carney, E.W.

2006-01-01

Reports of a decreased male/female sex ratio in children born to males exposed to TCDD in Seveso, Italy, at a young age have sparked examinations of this endpoint in other populations exposed to TCDD or related compounds. Overall, the male/female sex ratio results reported in these studies, with slightly different age-exposed male populations, have shown mixed results. Experimental studies of the effects of in utero exposure to TCDD in laboratory animals have reported no effect on the f 1 sex ratio and mixed results for the sex ratio of the f 2 generation. In order to better understand the potential effects of TCDD on second generation sex ratio, we retrieved archived data from a comprehensive three-generation feeding study of TCDD in rats that was conducted and published in the 1970s, but which did not publish data on sex ratio of the offspring [Murray, F.J., Smith, F.A., Nitschke, K.D., Humiston, C.G., Kociba, R.J., Schwetz, B.A., 1979. Three-generation reproduction study of rats given 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the diet. Toxicol. Appl. Pharmacol. 50, 241-252]. A re-examination of the original Murray et al. data found no statistically significant treatment-related changes in postnatal day 1 sex ratio in any generation of treated animals, consistent with one other relatively large study reporting on this endpoint. We discuss mechanistic data underlying a potential effect of TCDD on this endpoint. We conclude that the inconsistency in findings on sex ratio of the offspring of male rats exposed to TCDD in utero is likely due to random variation associated with a relatively small sample size, although differences between studies in strain of rat, dose regimen, and day of ascertainment of sex ratio cannot be ruled out

Unusually dynamic sex roles in a fish.

Science.gov (United States)

Forsgren, Elisabet; Amundsen, Trond; Borg, Asa A; Bjelvenmark, Jens

2004-06-03

Sex roles are typically thought of as being fixed for a given species. In most animals males compete for females, whereas the females are more reluctant to mate. Therefore sexual selection usually acts most strongly on males. This is explained by males having a higher potential reproductive rate than females, leading to more males being sexually active (a male-biased operational sex ratio). However, what determines sex roles and the strength of sexual selection is a controversial and much debated question. In this large-scale field study, we show a striking temporal plasticity in the mating competition of a fish (two-spotted goby, Gobiusculus flavescens). Over the short breeding season fierce male-male competition and intensive courtship behaviour in males were replaced by female-female competition and actively courting females. Hence, sex role reversal occurred rapidly. This is the first time that a shift in sex roles has been shown in a vertebrate. The shift might be explained by a large decline in male abundance, strongly skewing the sex ratio towards females. Notably, the sex role reversal did not occur at an equal operational sex ratio, contrary to established sex role theory.

Optimization of Sex Ratio in a Selection Plan for Palas Prolificacy Line

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Răzvan Popa

2011-05-01

Full Text Available The aim of the paper work is to optimize the sex ratio in a selection plan, according to model developed by King (1961, which will be proposed to be applied for prolificacy improvement in Prolific Line Palas. The method used in this paper work is modeling, which exist in the most animal breeding scientifically papers. After the simulations, we observed that the most convenient variant was that which prefigure use of 13 rams on reproduction activity. This variant offer a genetic gain per generation by 0.47497 additive standard deviations.

Colony size, sex ratio and cohabitation in roosts of Phyllostomus hastatus (Pallas (Chiroptera: Phyllostomidae

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LM. Costa

Full Text Available Phyllostomus hastatus bat is species broadly distributed over the Neotropical region, which uses as diurnal roosts caves, hollow trees, palm leaves and human buildings. Thirteen diurnal roosts of P. hastatus were analysed from 1990 to 2009 in several localities of Rio de Janeiro State, regarding environment (rural, urban or protected area, type of roost (hollow tree, basement or roof, sex ratio and cohabitation. A nocturnal roost was also analysed. Sex ratio of P. hastatus varied considerably among roosts what may be explained by the fact this species can roost alone, in couples, in harems or in groups of bachelor males. Phyllostomus hastatus was observed in cohabitation with three other species: Molossus rufus, Molossus molossus and Myotis nigricans. Due to the frequency of cohabitation observed between P. hastatus and species of the genus Molossus, one or more advantages for the members of this association may be expected. The simultaneous usage of a feeding roost by a group of bachelor males is unknown information in the literature, and may suggest that this kind of group may interact with each other even when away from their diurnal roosts.

Positive selection of deleterious alleles through interaction with a sex-ratio suppressor gene in African Buffalo: a plausible new mechanism for a high frequency anomaly.

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Pim van Hooft

Full Text Available Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer population of Kruger National Park, through positive selection of these alleles that is ultimately driven by a sex-ratio suppressor. We have previously shown that one in four Kruger buffalo has a Y-chromosome profile that, despite being associated with low body condition, appears to impart a relative reproductive advantage, and which is stably maintained through a sex-ratio suppressor. Apparently, this sex-ratio suppressor prevents fertility reduction that generally accompanies sex-ratio distortion. We hypothesize that this body-condition-associated reproductive advantage increases the fitness of alleles that negatively affect male body condition, causing genome-wide positive selection of these alleles. To investigate this we genotyped 459 buffalo using 17 autosomal microsatellites. By correlating heterozygosity with body condition (heterozygosity-fitness correlations, we found that most microsatellites were associated with one of two gene types: one with elevated frequencies of deleterious alleles that have a negative effect on body condition, irrespective of sex; the other with elevated frequencies of sexually antagonistic alleles that are negative for male body condition but positive for female body condition. Positive selection and a direct association with a Y-chromosomal sex-ratio suppressor are indicated, respectively, by allele clines and by relatively high numbers of homozygous deleterious alleles among sex-ratio suppressor carriers. This study, which employs novel statistical techniques to analyse heterozygosity-fitness correlations, is the first to demonstrate the abundance of sexually-antagonistic genes in a natural mammal population. It also has

Sex ratio of offspring and occupational exposure to fly ash : a historical cohort study of municipal solid waste incinerator workers in Japan

Energy Technology Data Exchange (ETDEWEB)

Mori, I.; Ogawa, Y. [National Inst. of Industrial Health, Tokyo (Japan); Kumagai, S. [Osaka Prefectural Inst. of Public Health, Osaka (Japan); Koda, S. [Kochi Medical School, Nangoku (Japan); Ueno, M. [All-Japan Prefectural and Municipal Workers Union, Tokyo (Japan)

2005-07-01

This paper described a cohort study which focused on risk assessment for cancer mortality and changes in the sex ratio of offspring among municipal solid waste incinerator (MSWI) workers in Japan. A baseline survey was conducted by survey with both MSWI workers as well as a reference population of waste collection workers. Questions were related to offspring, job history, and frequency of exposure to fly ash during incinerator work. A total of 5211 records were then analyzed as well as 10,571 children. Duration of exposure to fly ash was used as a surrogate exposure index. Results showed that longer exposure to fly ash influenced the sex ratio. Results of a multivariate analysis conducted to compute the odds ratio of female birth by different exposure indices were similar to results obtained in a univariate analysis. It was concluded that an association between duration of exposure to fly ash and changes in sex ratio was determined. 5 refs., 3 tabs.

Vaginal and Oral Sex Initiation Timing: A Focus on Gender and Race/Ethnicity.

Science.gov (United States)

Holway, Giuseppina Valle

2015-07-01

Most previous studies on sexual initiation timing have examined its effects on a variety of subsequent outcomes without first examining the correlates and predictors of these timing categories. Studies that do exist often do not utilize samples through young adulthood, leading to a misclassified set of sexual timing categories. In addition, the literature does not adequately address the issues of oral sex timing. Therefore, the objectives of this study were 1) to explore age-cutoffs that mark the "normative" and "non-normative" entry into vaginal and oral sex among young women and men in the U.S., creating sexual four sexual initiation timing categories - "early," "normative," "late," and "inexperienced," and; 2) to examine the association between race/ethnicity and sexual initiation timing by gender. The National Longitudinal Study of Adolescent to Adult Health (Add Health) was used in both descriptive and multivariate contexts to determine the net association of gender and race/ethnicity with vaginal and oral sex initiation timing. Age-cutoffs for vaginal sex timing were similar for women and men, yet differed by gender for oral sex timing. Women were more likely than men to initiate vaginal sex (20% vs. 18%) and oral sex (19% vs. 16%) at an early age and less likely than men to initiate these behaviors at a late age (18% vs. 19% for vaginal sex, and 15% vs. 16% for oral sex). Although most respondents initiated these two behaviors by young adulthood, a considerable proportion remained inexperienced, with men more likely than women to report inexperience with vaginal sex (7% vs. 5%), and women more likely than men to report abstaining from oral sex (8% vs. 6%). Race/ethnic differences in sexual initiation timing remained robust in the face of controls for both women and men. Understanding the timing at which adolescents and young adults transition to first vaginal and first oral sex is critical for sex education curriculum and policy makers.

Female biased sex-ratio in Schistosoma mansoni after exposure to an allopatric intermediate host strain of Biomphalaria glabrata.

Science.gov (United States)

Lepesant, Julie M J; Boissier, Jérôme; Climent, Déborah; Cosseau, Céline; Grunau, Christoph

2013-10-01

For parasites that require multiple hosts to complete their development, the interaction with the intermediate host may have an impact on parasite transmission and development in the definitive host. The human parasite Schistosoma mansoni needs two different hosts to complete its life cycle: the freshwater snail Biomphalaria glabrata (in South America) as intermediate host and a human or rodents as final host. To investigate the influence of the host environment on life history traits in the absence of selection, we performed experimental infections of two B. glabrata strains of different geographic origin with the same clonal population of S. mansoni. One B. glabrata strain is the sympatric host and the other one the allopatric host. We measured prevalence in the snail, the cercarial infectivity, sex-ratio, immunopathology in the final host and microsatellite frequencies of individual larvae in three successive generations. We show that, even if the parasite population is clonal based on neutral markers, S. mansoni keeps the capacity of generating phenotypic plasticity and/or variability for different life history traits when confront to an unusual environment, in this study the intermediate host. The most dramatic change was observed in sex-ratio: in average 1.7 times more female cercariae were produced when the parasite developed in an allopatric intermediate host. Copyright © 2013 Elsevier Inc. All rights reserved.

The Golden Ratio in Time-based Media

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Emily Verba

2013-06-01

Full Text Available Measure and proportion manifest themselves in all areas of beauty and virtue.–Socrates Mathematics and visual communication share a long historical, symbiotic relationship. In their pursuit of achieving order and beauty, they find common ground through geometry. The golden ratio is a mathematic and aesthetic phenomenon inherent in nature that has consistently evoked sensory enjoyment since antiquity. It may be assumed that the manifestation of the golden ratio in nature accounts for human’s innate enjoyment of it. Throughout the ages, the conscious application of the golden ratio to proportions found in art, architecture, poetry, literature and musical composition has consistently evoked subconscious sensory pleasure. However, the application of the golden ratio to visual temporal proportion, or time-based media, has seldom been investigated. This thesis investigates various applications of the golden ratio as a mathematical framework for choreographing visually harmonious temporal compositions through time-based media. The proliferation of moving images we face on a daily basis is cause for great concern, as we have increasingly less free time in our days. Informative and pleasing images are buried in an avalanche of visual rubbish, constantly streaming into our physical and virtual worlds. Time-based media has the ability to expand and contract movement, thus directing the way viewers experience and spend their time. This investigation presupposes that editing moving images via increments of time determined by the golden ratio may streamline messages, isolating what is most symbolic and effectively communicative within a mathematical framework. A physiological and psychological benefit is created for viewers; there is no wasted time or space. Image-makers and visual communicators have a responsibility to create only that which is useful and/or aesthetically pleasing. An investigation into the temporal structure of time-based media, using

Germ-line origins of mutation in families with hemophilia B: The sex ratio varies with the type of mutation

Energy Technology Data Exchange (ETDEWEB)

Ketterling, R.P.; Vielhaber, E.; Bottema, C.D.K.; Schaid, D.J.; Sommer, S.S. (Mayo Clinic/Foundation, Rochester, MN (United States)); Cohen, M.P. (Vanderbilt Univ., Nashville, TN (United States)); Sexauer, C.L. (Children' s Hospital, Oklahoma City, OK (United States))

1993-01-01

Previous epidemiological and biochemical studies have generated conflicting estimates of the sex ratio of mutation. Direct genomic sequencing in combination with haplotype analysis extends previous analyses by allowing the precise mutation to be determined in a given family. From analysis of the factor IX gene of 260 consecutive families with hemophilia B, the authors report the germ-line origin of mutation in 25 families. When combined with 14 origins of mutation reported by others and with 4 origins previously reported by them, a total of 25 occur in the female germ line, and 18 occur in the male germ line. The excess of germ-line origins in females does not imply an overall excess mutation rate per base pair in the female germ line. Bayesian analysis of the data indicates that the sex ratio varies with the type of mutation. The aggregate of single-base substitutions shows a male predominance of germ-line mutations (P < .002). The maximum-likelihood estimate of the male predominance is 3.5-fold. Of the single-base substitutions, deletions display a sex ratio of unity. Analysis of the parental age at transmission of a new mutation suggests that germ-line mutations are associated with a small increase in parental age in females but little, if any, increase in males. Although direct genomic sequencing offers a general method for defining the origin of mutation in specific families, accurate estimates of the sex ratios of different mutational classes require large sample sizes and careful correction for multiple biases of ascertainment. The biases in the present data result in an underestimate of the enhancement of mutation in males. 62 refs., 1 fig., 5 tabs.

Influence of Propylparaben on Vitellogenesis and Sex Ratio in Juvenile Zebrafish (Danio rerio

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Přemysl Mikula

2009-01-01

Full Text Available The aim of the study was to evaluate the xeno-oestrogenic potential of propylparaben in vivo using zebrafish (Danio rerio. Experimental juvenile zebrafish (20 days post hatching were fed a feed containing 500, 1000, or 2000 mg kg-1 of propylparaben, fish in a positive control group were given a feed treated with 20 mg kg-1 of 17β-oestradiol, and the control fish were given the feed free of either tested substance. The exposure of fish to propylparaben did not affect vitellogenesis after 20 days exposure but seemed to influence the sex differentiation processes, as evidenced by a sex ratio significantly skewed towards females in the group fed 500 mg kg-1 of propylparaben following 45 days of exposure. The potential of the fish to respond to oestrogenic stimulation was confirmed, since significantly higher vitellogenin concentrations were detected in the fish from the positive control group.

Juvenile exposure to vinclozolin shifts sex ratios and impairs reproductive capacity of zebrafish.

Science.gov (United States)

Lor, Yer; Revak, Andrew; Weigand, Jenna; Hicks, Elisabeth; Howard, David R; King-Heiden, Tisha C

2015-12-01

Exposure to endocrine disruptors during critical periods of development can impact the sustainability of wild fish populations. Anti-androgenic compounds have received less attention, but are capable of modulating gonad differentiation and maturation, and impairing reproduction in fish. The fungicide vinclozolin (VZ) has been shown to impair reproduction in adult fish, but less is known about its effects following exposure earlier in development. Here we show that waterborne exposure to 400μg VZ/L during critical periods of sex differentiation (21-35 days post fertilization) permanently shifts sex ratios towards females, and alters the maturation of the gonad. Both fecundity and fertility were reduced, even when oogenesis and spermatogenesis recover and sperm motility is not altered. These results demonstrate the need to better understand the impacts of early exposure to anti-androgenic compounds on fish. Copyright © 2015 Elsevier Inc. All rights reserved.

Flight patterns and sex ratio of beetles of the subfamily Dynastinae (Coleoptera, Melolonthidae

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Larissa Simões Corrêa de Albuquerque

2016-09-01

Full Text Available ABSTRACT Dynastinae is one of the most representative subfamilies of Melolonthidae (Scarabaeoidea and has considerable ecological importance due mainly to interactions with plants of the families Araceae and Annonaceae. This relationship has led to the evolution of nocturnal activity patterns, which are influenced by environmental conditions. In the present study, abiotic factors were investigated to comprehend the influence on the flight patterns and identify the sex ratio of beetles from this subfamily. A study was conducted at Campo de Instrução Marechal Newton Cavalcanti in northeastern Brazil between December 2010 and November 2011. Thirteen species of Dynastinae were identified, most of which were from the genus Cyclocephala. Abundance and richness were greater in the dry season. Six species exhibited peak flight activity at specific periods of the night. More females than males were recorded for Cyclocephala distincta and C. paraguayensis. The present findings suggest that rainfall reduces the flight activity of these beetles and different time schedules may be related to mating behavior, foraging behavior and the avoidance of interspecific resource competition.

Changing trend? Sex ratios of children born to Indian immigrants in Norway revisited.

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Tønnessen, Marianne; Aalandslid, Vebjørn; Skjerpen, Terje

2013-09-05

In some Western countries, a disturbingly low share of girls has been observed among new-borns from Indian immigrants. Also in Norway, a previous study based on figures from 1969-2005 showed a high percentage of boys among children of Indian origin living in Norway, when the birth was of higher order (third birth or later). This was suggested to reflect a practice of sex-selective abortions in the Indian immigrant population. In this article we have seen whether extended time series for the period 2006-2012 give further support to this claim. Based on data from the Norwegian Central Population Register we used observations for the sex of all live births in Norway for the period 1969-2012 where the mother was born in India. The percentage of boys was calculated for each birth order, during four sub periods. Utilising a binomial probability model we tested whether the observed sex differences among Indian-born women were significantly different from sex differences among all births. Contrary to findings from earlier periods and other Western countries, we found that Indian-born women in Norway gave birth to more girls than boys of higher order in the period 2006-2012. This is somewhat surprising, since sex selection is usually expected to be stronger if the mother already has two or more children. The extended time series do not suggest a prevalence of sex selective abortions among Indian-born women in Norway. We discuss whether the change from a majority of boys to a majority of girls in higher order could be explained by new waves of immigrant women, by new preferences among long-residing immigrant women in Norway - or by mere coincidence.

Changes in the sex ratio of the Common Pochard Aythya ferina in Europe and North Africa

NARCIS (Netherlands)

Brides, Kane; Wood, Kevin; Hearn, Richard; Fijen, T.P.M.

2017-01-01

Assessments of the sex ratio among Common Pochard Aythya ferina flocks were undertaken in countries across Europe and into North Africa in January 2016, for comparison with results from surveys carried out over the same area in January 1989 and January 1990. The mean (± 95% CI) proportions of males

Resisting the "Condom Every Time for Anal Sex" Health Education Message

Science.gov (United States)

Adams, Jeffery; Neville, Stephen

2012-01-01

Objective: Ensuring men who have sex with men (MSM) adopt and maintain condom use for anal sex is a challenging health education goal. In order to inform the development of social marketing practices to encourage safe-sex practices, the views of MSM about a key HIV health education message ("using a condom every time for anal sex") were…

Effect of estradiol-17β on the sex ratio, growth and survival of juvenile common snook (Centropomus undecimalis)

OpenAIRE

Cristina Vaz Avelar de Carvalho; Gabriel Passini; Wanessa de Melo Costa; Beatriz Nunes Vieira; Vinicius Ronzani Cerqueira

2014-01-01

Sex control in fish is a promising technique for aquaculture, since it gives advantages associated with one sex. The aim of this study was to investigate the feminization of common snook (Centropomus undecimalis) by oral administration of two doses of estradiol-17β (50 and 100 mg E2 kg-1 feed) and control treatment for 45 days and to evaluate their effects on the sex ratio, growth and survival of common snook juveniles. After this period, fish were fed only with commercial feed without hormon...

Influence of postzygotic reproductive isolation on the interspecific transmission of the paternal sex ratio chromosome in Trichogramma

NARCIS (Netherlands)

Jeong, G.S.; Stouthamer, R.

2006-01-01

The paternal sex ratio (PSR) chromosome is a supernumerary chromosome that causes the destruction of the paternal chromosome set in the first mitosis in a fertilized egg. It is known from parasitoid wasps in the genera Nasonia and Trichogramma (Hymenoptera). In these haplodiploids, the egg

The origin of a selfish B chromosome triggering paternal sex ratio in the parasitoid wasp Trichogramma kaykai

NARCIS (Netherlands)

Vugt, van J.J.F.A.; Jong, de J.H.S.G.M.; Stouthamer, R.

2009-01-01

This study uses molecular and cytogenetic methods to determine the origin of a B chromosome in some males of the wasp Trichogramma kaykai. This so-called paternal sex ratio (PSR) chromosome transmits only through sperm and shortly after fertilization triggers degeneration of the paternal genome,

Effect of semen quality on human sex ratio in in vitro fertilization and intracytoplasmic sperm injection: an analysis of 27,158 singleton infants born after fresh single-embryo transfer.

Science.gov (United States)

Arikawa, Mikiko; Jwa, Seung Chik; Kuwahara, Akira; Irahara, Minoru; Saito, Hidekazu

2016-04-01

To evaluate the effect of semen quality on human sex ratio in in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Retrospective cohort study. Not applicable. A total of 27,158 singleton infants born between 2007 and 2012 after fresh single-embryo transfer. None. Proportion of male infants among liveborn infants. There were 14,996 infants born after IVF, 12,164 infants born after ICSI with ejaculated sperm, and 646 infants born after ICSI with nonejaculated sperm. The sex ratio of IVF was 53.1% (95% confidence interval [CI], 52.3-53.9); the sex ratio of ICSI with ejaculated and nonejaculated sperm demonstrated as statistically significant reduction (48.2%; 95% CI, 47.3-49.1 and 47.7%; 95% CI, 43.8-51.6, respectively). In IVF, lower sperm motility, including asthenozoospermia (sperm motility ratio compared with normal sperm (51.0%; 95% CI, 48.6-53.3 vs. 53.4%; 95% CI, 52.5-54.3). In ICSI with ejaculated sperm, there was no association between sperm motility and sex ratio. Sperm concentration was not associated with sex ratio in both IVF and ICSI. In IVF, lower sperm motility was associated with a statistically significant reduction in sex ratio; ICSI with either ejaculated or nonejaculated sperm was associated with a statistically significant reduction in sex ratio regardless of semen quality. Copyright © 2016 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Socioeconomic status and sex ratios at birth in Sweden: No evidence for a Trivers-Willard effect for a wide range of status indicators.

Science.gov (United States)

Kolk, Martin; Schnettler, Sebastian

2016-01-01

This study examines if there exists a positive association between socioeconomic status and the proportion of male births in humans, as proposed by Trivers and Willard in 1973, using individual-level data drawn from the complete population of Sweden. We examine more than 3,000,000 births between 1960 and 2007 using administrative register data with comprehensive information on various dimensions of socioeconomic status. We use six different operationalizations of socioeconomic status, including earnings, post-transfer income (including government allowances), wealth, parental wealth, educational level, and occupational class. We apply regression models that compare both changes in status for the same woman over time and differences in status across different women. We also measure socioeconomic status both at the year of child birth and the year of conception. Our results show the absence of any relationship between socioeconomic status and sex ratios, using a large number of different operationalizations of status. We conclude that no substantive relationship between socioeconomic status and sex ratios exists for the population and period of our study. © 2015 Wiley Periodicals, Inc.

Pre-conception energy balance and secondary sex ratio--partial support for the Trivers-Willard hypothesis in dairy cows.

Science.gov (United States)

Roche, J R; Lee, J M; Berry, D P

2006-06-01

According to the Trivers-Willard hypothesis, maternal condition at or around conception affects the secondary sex ratio in mammals. However, there are little or no data available on indicators of maternal condition in dairy cows on the sex of the resultant offspring. A total of 76,607 body condition score (BCS; scale of 1 to 5) records and 76,611 body weight (BW) records from 3,209 lactations across 1,172 cows were extracted from a research database collated from one research herd between 1986 and 2004, inclusive. Exclusion of multiple births and cows with no information before calving (e.g., nulliparous animals) resulted in 2,029 records with BCS and BW observations from the previous calving, and 2,002 and 1,872 lactations with BCS and BW observations at conception and midgestation, respectively. Change in BCS and BW between calving and conception and between conception and midgestation was calculated per lactation. Generalized estimating equations were used to model the logit of the probability of a male calf, in which cow was included as a repeated effect with a first-order autoregressive correlation structure assumed among records within cow. Of the BCS variables investigated, there was a linear relationship between the logit of the probability of a male calf and BCS change between calving and conception, the rate of BCS change over this period (BCS divided by days in milk), and BCS at the calving event immediately before conception. The birth of a bull calf was 1.85 times more likely in cows that lost no BCS from calving to conception compared with cows that lost one BCS unit from calving to conception. This increase in odds was equivalent to a 14% unit increase in the probability of a male calf (from 54 to 68%). The amount of BW lost between calving and conception and the rate of loss affected the sex of the resultant offspring. Less BW loss or greater BW gain between calving and conception was associated with greater likelihood of a male calf. Results

Masculine sex ratios, population age structure and the potential spread of HIV in China

OpenAIRE

M. Giovanna Merli; Sara Hertog

2010-01-01

There is much speculation regarding the contribution of China's changing demography to the spread of HIV/AIDS. We employ a bio-behavioral macrosimulation model of the heterosexual spread of HIV/AIDS to evaluate the roles that China's unique demographic conditions -- (1) masculine sex ratios at birth and (2) a population age structure that reflects rapid fertility decline since the 1970's -- play in altering the market for sexual partners, thereby potentially fueling an increase...

Genetic Diversity of the Invasive Gall Wasp Leptocybe invasa (Hymenoptera: Eulophidae) and of its Rickettsia Endosymbiont, and Associated Sex-Ratio Differences

Science.gov (United States)

Nugnes, Francesco; Gebiola, Marco; Monti, Maurilia Maria; Gualtieri, Liberata; Giorgini, Massimo; Wang, Jianguo; Bernardo, Umberto

2015-01-01

The blue-gum chalcid Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae) is a gall wasp pest of Eucalyptus species, likely native to Australia. Over the past 15 years it has invaded 39 countries on all continents where eucalypts are grown. The worldwide invasion of the blue gum chalcid was attributed to a single thelytokous morphospecies formally described in 2004. Subsequently, however, males have been recorded in several countries and the sex ratio of field populations has been found to be highly variable in different areas. In order to find an explanation for such sex ratio differences, populations of L. invasa from a broad geographical area were screened for the symbionts currently known as reproductive manipulators, and both wasps and symbionts were genetically characterized using multiple genes. Molecular analyses suggested that L. invasa is in fact a complex of two cryptic species involved in the rapid and efficient spread of the wasp, the first recovered from the Mediterranean region and South America, the latter from China. All screened specimens were infected by endosymbiotic bacteria belonging to the genus Rickettsia. Two closely related Rickettsia strains were found, each infecting one of the two putative cryptic species of L. invasa and associated with different average sex ratios. Rickettsia were found to be localized in the female reproductive tissues and transovarially transmitted, suggesting a possible role of Rickettsia as the causal agent of thelytokous parthenogenesis in L. invasa. Implications for the variation of sex ratio and for the management of L. invasa are discussed. PMID:25970681

Genetic Diversity of the Invasive Gall Wasp Leptocybe invasa (Hymenoptera: Eulophidae and of its Rickettsia Endosymbiont, and Associated Sex-Ratio Differences.

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Francesco Nugnes

Full Text Available The blue-gum chalcid Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae is a gall wasp pest of Eucalyptus species, likely native to Australia. Over the past 15 years it has invaded 39 countries on all continents where eucalypts are grown. The worldwide invasion of the blue gum chalcid was attributed to a single thelytokous morphospecies formally described in 2004. Subsequently, however, males have been recorded in several countries and the sex ratio of field populations has been found to be highly variable in different areas. In order to find an explanation for such sex ratio differences, populations of L. invasa from a broad geographical area were screened for the symbionts currently known as reproductive manipulators, and both wasps and symbionts were genetically characterized using multiple genes. Molecular analyses suggested that L. invasa is in fact a complex of two cryptic species involved in the rapid and efficient spread of the wasp, the first recovered from the Mediterranean region and South America, the latter from China. All screened specimens were infected by endosymbiotic bacteria belonging to the genus Rickettsia. Two closely related Rickettsia strains were found, each infecting one of the two putative cryptic species of L. invasa and associated with different average sex ratios. Rickettsia were found to be localized in the female reproductive tissues and transovarially transmitted, suggesting a possible role of Rickettsia as the causal agent of thelytokous parthenogenesis in L. invasa. Implications for the variation of sex ratio and for the management of L. invasa are discussed.

Reproductive behaviour of female rosy bitterling Rhodeus ocellatus in response to a female-biased operational sex ratio

Czech Academy of Sciences Publication Activity Database

Liao, C.; Yu, D.; Chen, Y.; Reichard, Martin; Liu, H.

2014-01-01

Roč. 151, č. 6 (2014), s. 755-768 ISSN 0005-7959 R&D Projects: GA ČR GBP505/12/G112 Institutional support: RVO:68081766 Keywords : alternative reproductive behaviour * female aggression * operational sex ratio * bitterling Subject RIV: EG - Zoology Impact factor: 1.230, year: 2014

A framework for analyzing sex-selective abortion: the example of changing sex ratios in Southern Caucasus

Science.gov (United States)

Hohmann, Sophie A; Lefèvre, Cécile A; Garenne, Michel L

2014-01-01

The paper proposes a socioeconomic framework of supply, demand, and regulation to explain the development of sex-selective abortion in several parts of the world. The framework is then applied to three countries of southern Caucasus (Armenia, Azerbaijan, and Georgia) where sex-selective abortion has developed since the collapse of the Soviet Union. The authors argue that sex-selective abortion cannot be explained simply by patriarchal social systems, sex discrimination, or son preference. The emphasis is put on the long-term acceptability of abortion in the region, on acceptability of sex-screening by both the medical establishment and by the population, on newly imported techniques of sex-screening, and on the changing demand for children associated with the major economic and social changes that followed the dismantlement of the Soviet Union. PMID:25349481

Status hierarchy, attractiveness hierarchy and sex ratio : Three contextual factors explaining the status-aggression link among adolescents

NARCIS (Netherlands)

Zwaan, Michiel; Dijkstra, Jan; Veenstra, René

The moderating effects of three specific conditions (status hierarchy, attractiveness hierarchy and sex ratio) on the link between status (popularity) and physical and relational aggression were examined in a large sample of adolescent boys (N = 1,665) and girls (N = 1,637) (M age = 13.60). In line

Reproductive seasonality, sex ratio and philopatry in Argentina's common vampire bats

Science.gov (United States)

Delpietro, H. A.; Russo, R. G.; Lord, R. D.; Delpietro, G. L.

2017-01-01

Common vampire bats (Desmodus rotundus) are a key rabies vector in South America. Improved management of this species requires long-term, region-specific information. To investigate patterns of demography and dispersal, we analysed 13 642 captures of common vampire bats in Northern Argentina from the period 1969–2004. In contrast with findings from more tropical regions, we found reproductive seasonality with peak pregnancy in September and peak lactation in February. Curiously, sex ratios were consistently male-biased both in maternity roosts and at foraging sites. Males comprised 57% of 9509 adults caught at night, 57% of 1078 juveniles caught at night, 57% of 603 juveniles caught in roosts during the day, and 55% of 103 newborns and mature fetuses. Most observed roosts were in man-made structures. Movements of 1.5–54 km were most frequent in adult males, followed by young males, adult females and young females. At night, males visited maternity roosts, and non-pregnant, non-lactating females visited bachelor roosts. Males fed earlier in the night. Finally, we report new longevity records for free-ranging vampire bats: 16 and 17 years of age for a female and male, respectively. Our results are consistent with model predictions that sex-biased movements might play a key role in rabies transmission between vampire bat populations. PMID:28484615

Reproductive seasonality, sex ratio and philopatry in Argentina's common vampire bats.

Science.gov (United States)

Delpietro, H A; Russo, R G; Carter, G G; Lord, R D; Delpietro, G L

2017-04-01

Common vampire bats ( Desmodus rotundus ) are a key rabies vector in South America. Improved management of this species requires long-term, region-specific information. To investigate patterns of demography and dispersal, we analysed 13 642 captures of common vampire bats in Northern Argentina from the period 1969-2004. In contrast with findings from more tropical regions, we found reproductive seasonality with peak pregnancy in September and peak lactation in February. Curiously, sex ratios were consistently male-biased both in maternity roosts and at foraging sites. Males comprised 57% of 9509 adults caught at night, 57% of 1078 juveniles caught at night, 57% of 603 juveniles caught in roosts during the day, and 55% of 103 newborns and mature fetuses. Most observed roosts were in man-made structures. Movements of 1.5-54 km were most frequent in adult males, followed by young males, adult females and young females. At night, males visited maternity roosts, and non-pregnant, non-lactating females visited bachelor roosts. Males fed earlier in the night. Finally, we report new longevity records for free-ranging vampire bats: 16 and 17 years of age for a female and male, respectively. Our results are consistent with model predictions that sex-biased movements might play a key role in rabies transmission between vampire bat populations.

Low reproductive skew despite high male-biased operational sex ratio in a glass frog with paternal care.

Science.gov (United States)

Mangold, Alexandra; Trenkwalder, Katharina; Ringler, Max; Hödl, Walter; Ringler, Eva

2015-09-03

Reproductive skew, the uneven distribution of reproductive success among individuals, is a common feature of many animal populations. Several scenarios have been proposed to favour either high or low levels of reproductive skew. Particularly a male-biased operational sex ratio and the asynchronous arrival of females is expected to cause high variation in reproductive success among males. Recently it has been suggested that the type of benefits provided by males (fixed vs. dilutable) could also strongly impact individual mating patterns, and thereby affecting reproductive skew. We tested this hypothesis in Hyalinobatrachium valerioi, a Neotropical glass frog with prolonged breeding and paternal care. We monitored and genetically sampled a natural population in southwestern Costa Rica during the breeding season in 2012 and performed parentage analysis of adult frogs and tadpoles to investigate individual mating frequencies, possible mating preferences, and estimate reproductive skew in males and females. We identified a polygamous mating system, where high proportions of males (69 %) and females (94 %) reproduced successfully. The variance in male mating success could largely be attributed to differences in time spent calling at the reproductive site, but not to body size or relatedness. Female H. valerioi were not choosy and mated indiscriminately with available males. Our findings support the hypothesis that dilutable male benefits - such as parental care - can favour female polyandry and maintain low levels of reproductive skew among males within a population, even in the presence of direct male-male competition and a highly male-biased operational sex ratio. We hypothesize that low male reproductive skew might be a general characteristic in prolonged breeders with paternal care.

Sex ratio and breeding of white-lipped peccaries Tayassu pecari (Artiodactyla: Tayassuidae in a Costa Rican rain forest

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Mariana Altrichter

2001-03-01

Full Text Available White-lipped peccaries are non-seasonal breeders in South America, but little is known about their reproduction in Central America. There are few studies about the sex ratio of this species in the field. We studied the reproduction and sex ratio of white-lipped peccaries during 200 hours of field observation of four radiomarked and two unmarked herds, from July 1996 to April 1997, in Corcovado National Park, Costa Rica. Sex ratio data of three additional, radiomarked herds observed in 1998 were also included. We recorded numbers of mountings, presence of newborns and numbers of nursing interactions. The peccaries showed a distinct reproductive seasonality, with one mating peak in February and another in July. The greatest number of newborns and the peak in nursing activity were observed during July and August, when fruit availability for the peccaries was high. The adult sex ratio was significantly female biased (1.4:1 - 1.8:1, also in contrast with South American populations.Los "chanchos cariblancos" Tayassu pecari no son reproductores estacionales en Sur América. En Centro América se conoce muy poco sobre la reproducción de esta especie en la naturaleza. Estudiamos reproducción y la proporción de sexos durante 200 horas de observación de cuatro manadas marcadas con radiocollares y de dos manadas sin marcar, desde julio de 1996 hasta abril de 1997 en el Parque Nacional Corcovado, Costa Rica, agregando datos de proporción sexual de tres manadas observadas en 1998. Registramos el número de cópulas y de amamantamientos, así como la presencia de recién nacidos en las manadas. Observamos una marcada estacionalidad en la reproducción, con un pico en el número de cópulas en febrero y otro en julio. La mayor cantidad de recién nacidos y el pico de actividad de amamantamiento fueron en julio y agosto, cuando la disponibilidad de alimento era alta. Entre adultos predominaron numéricamente las hembras (1.4:1 - 1.8:1, lo cual difiere de lo

Status Hierarchy, Attractiveness Hierarchy and Sex Ratio: Three Contextual Factors Explaining the Status-Aggression Link among Adolescents

Science.gov (United States)

Zwaan, Michiel; Dijkstra, Jan Kornelis; Veenstra, Rene

2013-01-01

The moderating effects of three specific conditions (status hierarchy, attractiveness hierarchy and sex ratio) on the link between status (popularity) and physical and relational aggression were examined in a large sample of adolescent boys ("N" = 1,665) and girls ("N" = 1,637) ("M" age = 13.60). In line with the…

Polybrominated diphenyl ethers affect the reproduction and development, and alter the sex ratio of zebrafish (Danio rerio)

International Nuclear Information System (INIS)

Han, X.B.; Yuen, Karen W.Y.; Wu, Rudolf S.S.

2013-01-01

Polybrominated diphenyl ethers (PBDEs) have been commonly used as flame retardants and now become ubiquitous in the global environment. Using zebrafish as a model, we tested the hypothesis that PBDEs may affect the reproduction and development of fish. Zebrafish were exposed to environmentally relevant concentrations of DE-71 (a congener of PBDE commonly found in the environment) throughout their whole life cycle, and the effects of DE-71 on gonadal development, gamete quality, fertilization success, hatching success, embryonic development and sex ratio were investigated. Despite gonadal development was enhanced, reductions in spawning, fertilization success, hatching success and larval survival rate were evident, while significant increases in malformation and percentage of male were also observed in the F1 generation. Our laboratory results suggest that PBDEs may pose a risk to reproductive success and alter the sex ratio of fish in environments highly contaminated with PBDEs. -- Highlights: •Zebrafish were exposed to PBDE from eggs to adults. •An increase in Gonadal-Somatic Index and enhanced gonadal development was enhanced. •Fertilization and hatching successes were reduced, while malformation was increased. •PBDE alters sex differentiation, leading to a male biased F1 population. •Environmental relevant concentrations of PBDE threaten natural fish populations. -- PBDE reduces fertilization and hatching successes, causes malformation and leads to a male biased F1 generation in fish

Sex-role reversal of a monogamous pipefish without higher potential reproductive rate in females.

Science.gov (United States)

Sogabe, Atsushi; Yanagisawa, Yasunobu

2007-12-07

In monogamous animals, males are usually the predominant competitors for mates. However, a strictly monogamous pipefish Corythoichthys haematopterus exceptionally exhibits a reversed sex role. To understand why its sex role is reversed, we measured the adult sex ratio and the potential reproductive rate (PRR), two principal factors influencing the operational sex ratio (OSR), in a natural population of southern Japan. The adult sex ratio was biased towards females throughout the breeding season, but the PRR, which increased with water temperature, did not show sexual difference. We found that an alternative index of the OSR (Sf/Sm: sex ratio of 'time in') calculated from the monthly data was consistently biased towards females. The female-biased OSR associated with sex-role reversal has been reported in some polyandrous or promiscuous pipefish, but factors biasing the OSR differed between these pipefish and C. haematopterus. We concluded that the similar PRR between the sexes in C. haematopterus does not confer reproductive benefit of polygamous mating on either sex, resulting in strict monogamous mating, and its female-biased adult sex ratio promotes female-female competition for a mate, resulting in sex-role reversal.

Data storage on Russian pesticide producers exposed to dioxin. Sex ratios of third generation of Russian cohort

Energy Technology Data Exchange (ETDEWEB)

Amirova, Z.; Kruglov, E. [Environmental Research and Protection Center, Ufa (Russian Federation); Dardynskaia, I. [Univ. of Illinois, School of Public Health, Chicago (United States)

2004-09-15

A cohort of Russian workers who produced 2,4,5-T and 2,4,5-TrCP at a chemical factory in Ufa was brought to light in the papers of A. Schecter, J. Ryan and O. Papke. Dioxin exposure was experimentally confirmed by PCDD/Fs determination in blood samples first for a small group of workers and their children. This study permitted to connect the information of medical institutions about chloracne from which a group of young 2,4,5-T workers suffered in 1965-67 with exposure to dioxin. This report presents the results of the detailed study of the third generation of the Russian cohort (247 workers, 314 children and 260 grandchildren). We also present the data on the sex ratio of the second generation for the initial group enlarged by 25% as compared with the group of workers analyzed by J. Ryan et al. (198 workers and 227 children). Besides, as skewed sex ratio had earlier been stated only for paternal descendants, genealogical branches of the cohort representatives were studied.

On the masculinization of population: The contribution of demographic development -- A look at sex ratios in Sweden over 250 years

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Thomas Spoorenberg

2016-06-01

Full Text Available Background: Almost everywhere, women live longer than men, but the world population includes increasingly more men than women. This fact is observed not only in populations where gender-based discrimination is practised, but also in developed countries like Sweden. Objective: Whereas discrimination against female infants and women is usually given as an explanation for this paradox, demographic development (through improved survival also plays a role. This study examines the largely unnoticed role of demographic development in the masculinization of population, taking the case of Sweden. Methods: Using high-quality data from the Human Mortality Database for Sweden over the last 250 years, changes in the sex ratio at various ages are described and linked to the continuing survival gains achieved over the mortality transition. Results: Thanks to the reduction of secular mortality in Sweden, the natural sex imbalance observed at birth has been progressively prolonged later in life, and the age at which women outnumber men has been postponed to older ages. Similar developments are found in Norway and Denmark. Conclusions: The general decline of mortality is one of humanity's biggest achievements, but the accompanying change in age- and sex-specific survival patterns, coupled with the natural sex imbalance at birth, influences the age and sex composition of a population and, therefore, the sex ratio at successive ages. In a world where each new generation can expect to enjoy a longer life than the previous one, an increasing number of men can also be expected. Contribution: The role of demographic development in the masculinization of population has remained largely unnoticed so far.

Effects of a sex-ratio distorting endosymbiont on mtDNA variation in a global insect pest

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Cook James M

2009-03-01

Full Text Available Abstract Background Patterns of mtDNA variation within a species reflect long-term population structure, but may also be influenced by maternally inherited endosymbionts, such as Wolbachia. These bacteria often alter host reproductive biology and can drive particular mtDNA haplotypes through populations. We investigated the impacts of Wolbachia infection and geography on mtDNA variation in the diamondback moth, a major global pest whose geographic distribution reflects both natural processes and transport via human agricultural activities. Results The mtDNA phylogeny of 95 individuals sampled from 10 countries on four continents revealed two major clades. One contained only Wolbachia-infected individuals from Malaysia and Kenya, while the other contained only uninfected individuals, from all countries including Malaysia and Kenya. Within the uninfected group was a further clade containing all individuals from Australasia and displaying very limited sequence variation. In contrast, a biparental nuclear gene phylogeny did not have infected and uninfected clades, supporting the notion that maternally-inherited Wolbachia are responsible for the mtDNA pattern. Only about 5% (15/306 of our global sample of individuals was infected with the plutWB1 isolate and even within infected local populations, many insects were uninfected. Comparisons of infected and uninfected isofemale lines revealed that plutWB1 is associated with sex ratio distortion. Uninfected lines have a 1:1 sex ratio, while infected ones show a 2:1 female bias. Conclusion The main correlate of mtDNA variation in P. xylostella is presence or absence of the plutWB1 infection. This is associated with substantial sex ratio distortion and the underlying mechanisms deserve further study. In contrast, geographic origin is a poor predictor of moth mtDNA sequences, reflecting human activity in moving the insects around the globe. The exception is a clade of Australasian individuals, which may

Mapping Causes and Implications of India’s Skewed Sex Ratio and Poverty problem using Fuzzy & Neutrosophic Relational Maps

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Gaurav

2016-08-01

Full Text Available Numerous studies by different researchers have confirmed that skewed sex ratio is a critical social problem in India. This enduring problem of gender imbalance is the collective result of factors like sex selective abortion, gender discrimination, son preference for the preservation of tribe, emergence of new technologies in medical field and many more factors. Another severe problem to be addressed in India is poverty. Many factors contribute to the perpetuation of poverty such as illiteracy, bad governance, under employment and various other reasons. Despite of India's accelerated growth rate, poverty in India is still prevalent.

Age at sexual maturity, sex ratio, fecundity, and longevity of isolated headwater populations of westslope cutthroat trout

Science.gov (United States)

Christopher C. Downs; Robert G. White; Bradley B. Shepard

1997-01-01

We sampled 19 isolated headwater populations of westslope cutthroat trout Oncorhynchus clarki lewisi in Montana to provide estimates of fecundity, longevity, sex ratio, and age at sexual maturity. Fecundity was estimated for 31 fish collected from two streams in the upper Missouri River drainage. Females smaller than 149 mm fork length (FL) were generally immature and...

A Research Note on Time With Children in Different- and Same-Sex Two-Parent Families.

Science.gov (United States)

Prickett, Kate C; Martin-Storey, Alexa; Crosnoe, Robert

2015-06-01

Public debate on same-sex marriage often focuses on the disadvantages that children raised by same-sex couples may face. On one hand, little evidence suggests any difference in the outcomes of children raised by same-sex parents and different-sex parents. On the other hand, most studies are limited by problems of sample selection and size, and few directly measure the parenting practices thought to influence child development. This research note demonstrates how the 2003-2013 American Time Use Survey (n=44,188) may help to address these limitations. Two-tier Cragg's Tobit alternative models estimated the amount of time that parents in different-sex and same-sex couples engaged in child-focused time. Women in same-sex couples were more likely than either women or men in different-sex couples to spend such time with children. Overall, women (regardless of the gender of their partners) and men coupled with other men spent significantly more time with children than men coupled with women, conditional on spending any child-focused time. These results support prior research that different-sex couples do not invest in children at appreciably different levels than same-sex couples. We highlight the potential for existing nationally representative data sets to provide preliminary insights into the developmental experiences of children in nontraditional families.

Mode of action, origin and structure of the Paternal Sex Ratio chromosome in the parasitoid wasp Trichogramma kaykai

NARCIS (Netherlands)

Vugt, van J.J.F.A.

2005-01-01

Selfish genetic elements are defined as genetic elements that have a replication advantage relative to the rest of the genome. They are ubiquitous in nature and were extensively reported for almost all species studied so far. A special type of selfish genetic element, the sex ratio distorter, is

Female bias in the adult sex ratio of African annual fishes: interspecific differences, seasonal trends and environmental predictors

Czech Academy of Sciences Publication Activity Database

Reichard, Martin; Polačik, Matej; Blažek, Radim; Vrtílek, Milan

2014-01-01

Roč. 28, č. 6 (2014), s. 1105-1120 ISSN 0269-7653 R&D Projects: GA ČR(CZ) GAP506/11/0112 Institutional support: RVO:68081766 Keywords : Killifish * Tertiary sex ratio * Predator bias * Temporary savanna pools * Demographic consequences Subject RIV: EG - Zoology Impact factor: 2.517, year: 2014

DNA methylation of the gonadal aromatase (cyp19a promoter is involved in temperature-dependent sex ratio shifts in the European sea bass.

Directory of Open Access Journals (Sweden)

Laia Navarro-Martín

2011-12-01

Full Text Available Sex ratio shifts in response to temperature are common in fish and reptiles. However, the mechanism linking temperature during early development and sex ratios has remained elusive. We show in the European sea bass (sb, a fish in which temperature effects on sex ratios are maximal before the gonads form, that juvenile males have double the DNA methylation levels of females in the promoter of gonadal aromatase (cyp19a, the enzyme that converts androgens into estrogens. Exposure to high temperature increased the cyp19a promoter methylation levels of females, indicating that induced-masculinization involves DNA methylation-mediated control of aromatase gene expression, with an observed inverse relationship between methylation levels and expression. Although different CpGs within the sb cyp19a promoter exhibited different sensitivity to temperature, we show that the increased methylation of the sb cyp19a promoter, which occurs in the gonads but not in the brain, is not a generalized effect of temperature. Importantly, these effects were also observed in sexually undifferentiated fish and were not altered by estrogen treatment. Thus, methylation of the sb cyp19a promoter is the cause of the lower expression of cyp19a in temperature-masculinized fish. In vitro, induced methylation of the sb cyp19a promoter suppressed the ability of SF-1 and Foxl2 to stimulate transcription. Finally, a CpG differentially methylated by temperature and adjacent to a Sox transcription factor binding site is conserved across species. Thus, DNA methylation of the aromatase promoter may be an essential component of the long-sought-after mechanism connecting environmental temperature and sex ratios in vertebrate species with temperature-dependent sex determination.

Sex Partner Meeting Places Over Time Among Newly HIV-Diagnosed Men Who Have Sex With Men in Baltimore, Maryland.

Science.gov (United States)

Jennings, Jacky M; Reilly, Meredith L; Perin, Jamie; Schumacher, Christina; Sharma, Megha; Safi, Amelia Greiner; Fields, Errol L; Muvva, Ravikiran; Nganga-Good, Carolyn; Chaulk, Patrick

2015-10-01

Sex partner meeting places may be important locales to access men who have sex with men (MSM) and implement targeted HIV control strategies. These locales may change over time, but temporal evaluations have not been performed. The objectives of this study were to describe the frequency of report of MSM sex partner meeting places over time and to compare frequently reported meeting places in the past 5 years and past year among newly HIV-diagnosed MSM in Baltimore City, Maryland. Public health HIV surveillance data including partner services information were obtained for this study from the Baltimore City Health Department from May 2009 to June 2014. A total of 869 sex partner meeting places were reported, including 306 unique places. Bars/clubs (31%) and Internet-based sites (38%) were the most frequently reported meeting place types. Over the 5-year period, the percentage of bars/clubs decreased over time and the percentage of Internet-based sites increased over time. Among bars/clubs, 4 of 5 of those most frequently reported in the past 5 years were also most frequently reported in the most recent year. Among Internet-based sites, 3 of 5 of those most frequently reported in the past 5 years were also in the top 5 most frequently reported in the past year. This study provides a richer understanding of sex partner meeting places reported by MSM over time and information to health departments on types of places to access a population at high risk for HIV transmission.

Transcriptome profiling of Nasonia vitripennis testis reveals novel transcripts expressed from the selfish B chromosome, paternal sex ratio.

Science.gov (United States)

Akbari, Omar S; Antoshechkin, Igor; Hay, Bruce A; Ferree, Patrick M

2013-09-04

A widespread phenomenon in nature is sex ratio distortion of arthropod populations caused by microbial and genetic parasites. Currently little is known about how these agents alter host developmental processes to favor one sex or the other. The paternal sex ratio (PSR) chromosome is a nonessential, paternally transmitted centric fragment that segregates in natural populations of the jewel wasp, Nasonia vitripennis. To persist, PSR is thought to modify the hereditary material of the developing sperm, with the result that all nuclear DNA other than the PSR chromosome is destroyed shortly after fertilization. This results in the conversion of a fertilized embryo--normally a female--into a male, thereby insuring transmission of the "selfish" PSR chromosome, and simultaneously leading to wasp populations that are male-biased. To begin to understand this system at the mechanistic level, we carried out transcriptional profiling of testis from WT and PSR-carrying males. We identified a number of transcripts that are differentially expressed between these conditions. We also discovered nine transcripts that are uniquely expressed from the PSR chromosome. Four of these PSR-specific transcripts encode putative proteins, whereas the others have very short open reading frames and no homology to known proteins, suggesting that they are long noncoding RNAs. We propose several different models for how these transcripts could facilitate PSR-dependent effects. Our analyses also revealed 15.71 MB of novel transcribed regions in the N. vitripennis genome, thus increasing the current annotation of total transcribed regions by 53.4%. Finally, we detected expression of multiple meiosis-related genes in the wasp testis, despite the lack of conventional meiosis in the male sex.

Pregravid hypertension may have different secondary sex ratio effects in different races in the United States.

Science.gov (United States)

Grech, Victor

2017-12-01

Males are born in excess of females and the ratio is expressed as M/F (male/female births=secondary sex ratio, also known as secondary sex ratio). This is expected to approximate 1.048. Racial M/F disparities are known. A recent study in China showed that pregravid systolic hypertension is higher in women who delivered a boy than in those who had a girl. This study was carried out in order to identify the effect of pregravid hypertension in the United States on M/F by race. Monthly male and female live births by race for the entire US along with the presence/absence of hypertension were obtained from the website of the Centers for Disease Control and Prevention for 2007-2015 for the four racial groups: American Indian or Alaska Native, Asian or Pacific Islander, Black or African American and White. This study analysed 36,364,253 live births. For White births, mothers who had chronic hypertension were likelier to have male than female offspring when compared to non-hypertensives (p=0.003). Conversely, Black or African American mothers who had hypertension were less likely to have male than female offspring when compared to non-hypertensives (p=0.022). There were F differences for/F differences for the presence or absence of hypertension for the other two races or for the total. It is possible that hypothesised innate interracial periconceptual hormonal differences may modulate M/F responses to hypertension in different races. Copyright © 2017 Elsevier B.V. All rights reserved.

Impacts of temperature and crowding on sex ratio, fecundity and Wolbachia infection intensity in the copepod, Mesocyclops thermocyclopoides.

Science.gov (United States)

Wiwatanaratanabutr, Itsanun; Grandjean, Frederic

2016-11-01

Wolbachia are a group of intracellular bacteria that cause reproductive alterations in arthropods. Here, we describe the effects of two environmental factors (crowding and temperature) on phenotypic expression of feminization, the host's fecundity and Wolbachia infection intensity among life cycle stages in the naturally Wolbachia-infected copepod, Mesocyclops thermocyclopoides. The copepod was first found to be co-infected with Wolbachia A- and B-supergroups Wolbachia strains based on wsp primers. The relative Wolbachia infection intensity within individuals was determined using quantitative real-time PCR and was significantly higher in the B-supergroup than in the A-supergroup. Experimental results of temperature effect on bacterial density in each developmental stage revealed a significant decrease in Wolbachia infection intensity following exposure to high temperature (37°C) in both sexes and implied that Wolbachia might survive in room temperature (25°C) better than in high temperature. Experimental results of crowding effects on Wolbachia infection intensity suggested a negative correlation between copepod nauplii and Wolbachia infection intensity. No effect of rearing temperature on the sex ratio was reported although the fecundity was significantly decreased by high temperature. The results showed that Wolbachia infection intensity to be correlated with crowding conditions and was decreased following exposure of elevated temperature. Copyright © 2016 Elsevier Inc. All rights reserved.

The Golden Ratio in Time-based Media

Directory of Open Access Journals (Sweden)

Emily Verba

2013-06-01

The proliferation of moving images we face on a daily basis is cause for great concern, as we have increasingly less free time in our days. Informative and pleasing images are buried in an avalanche of visual rubbish, constantly streaming into our physical and virtual worlds. Time-based media has the ability to expand and contract movement, thus directing the way viewers experience and spend their time. This investigation presupposes that editing moving images via increments of time determined by the golden ratio may streamline messages, isolating what is most symbolic and effectively communicative within a mathematical framework. A physiological and psychological benefit is created for viewers; there is no wasted time or space. Image-makers and visual communicators have a responsibility to create only that which is useful and/or aesthetically pleasing. An investigation into the temporal structure of time-based media, using mathematical algorithms derived from the golden ratio, has led to the aim of creating through it a viable solution for the implementation of visual communication messages in today's society.

Are environmental factors responsible for geographic variation in the sex ratio of the Greenlandic seed-bug Nysius groenlandicus?

DEFF Research Database (Denmark)

Bøcher, Jens Jensenius; Nachman, Gøsta Støger

2010-01-01

Until recently nothing indicated an unequal sex ratio in the widespread Greenland seed-bug Nysius groenlandicus (Zetterstedt) (Heteroptera: Lygaeidae). However, recently populations more or less devoid of males were discovered in high arctic Northeast Greenland. This initiated an inspection of th...

Parental behaviour is unrelated to experimentally manipulated great tit brood sex ratio

NARCIS (Netherlands)

Lessells, C.M.; Oddie, K.R.; Mateman, A.C.

1998-01-01

Parental investment may be biased with respect to parental sex or offspring sex or there may be an interaction between parental and offspring sex. We investigated whether any of these types of bias occurred in great tits, Parus major. By sexing chicks using random amplified polymorphic DNA (RAPD)

Sex differences in college students' free drawings and their relationship to 2D:4D ratio and recalled childhood play behavior.

Science.gov (United States)

Rothkopf, Ian; Turgeon, Sarah M

2014-02-01

In a prior study, we observed that female-typical characteristics in elementary school girls' drawings were correlated with a feminized digit ratio (2D:4D), a marker for prenatal androgen exposure. However, this observation was limited to older girls, suggesting that social factors mediate the relationship between 2D:4D and drawing. To examine the hypothesis that the influence of prenatal androgen on girls' drawing is mediated by an effect of early androgens on sex-typical behavior, we examined 2D:4D, free drawings, and scores on the Recalled Childhood Gender Identity (RCGI) Questionnaire in a population of college students. Characteristics of participants' free drawings were assessed and those that showed sex differences were compared with 2D:4D and RCGI scores. Men had smaller 2D:4D ratios than women, used fewer total colors, used fewer pinks, purples, and blues, and had higher gender-typical scores on the RCGI. Women's drawings were more likely to contain flowers and animals and men's drawings were more likely to represent sports. Within-sex RCGI and 2D:4D scores were not significantly correlated. Significant within-sex relationships between 2D:4D and RCGI and drawing behavior were observed but the effects appeared to be independent; the hypothesis that gender-typical childhood behavior mediates the effect of prenatal androgen on drawing characteristics was not supported.

Shared genetic aetiology of puberty timing between sexes and with health-related outcomes.

Science.gov (United States)

Day, Felix R; Bulik-Sullivan, Brendan; Hinds, David A; Finucane, Hilary K; Murabito, Joanne M; Tung, Joyce Y; Ong, Ken K; Perry, John R B

2015-11-09

Understanding of the genetic regulation of puberty timing has come largely from studies of rare disorders and population-based studies in women. Here, we report the largest genomic analysis for puberty timing in 55,871 men, based on recalled age at voice breaking. Analysis across all genomic variants reveals strong genetic correlation (0.74, P=2.7 × 10(-70)) between male and female puberty timing. However, some loci show sex-divergent effects, including directionally opposite effects between sexes at the SIM1/MCHR2 locus (Pheterogeneity=1.6 × 10(-12)). We find five novel loci for puberty timing (Ppuberty, LEPR and KAL1. Finally, we identify genetic correlations that indicate shared aetiologies in both sexes between puberty timing and body mass index, fasting insulin levels, lipid levels, type 2 diabetes and cardiovascular disease.

Where is the bride? Progressively declining sex ratio in India: an alarming signal for imbalanced society

OpenAIRE

Nirmala Sharma; Kana Ram; Anand Sharma; Shashi Sharma

2014-01-01

Female feticide is an extreme form of violence against women, the most active part is being played by the women themselves just for the mere want of a boy, mothers dont feel bad in strangulating their own daughters in their wombs. From decades of sex determination and female feticide is creating a statistical imbalance regarding the commonly expected and lsquo;male: female' birth ratio in India. This offense have been spreaded to the states in India like Punjab, Haryana, Delhi, Gujarat and R...

Sex, age, pubertal development and use of oral contraceptives in relation to serum concentrations of DHEA, DHEAS, 17α-hydroxyprogesterone, Δ4-androstenedione, testosterone and their ratios in children, adolescents and young adults.

Science.gov (United States)

Søeborg, Tue; Frederiksen, Hanne; Mouritsen, Annette; Johannsen, Trine Holm; Main, Katharina Maria; Jørgensen, Niels; Petersen, Jørgen Holm; Andersson, Anna-Maria; Juul, Anders

2014-11-01

The influence of sex, age, pubertal development and oral contraceptives on dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), 17α-hydroxyprogesterone (17-OHP), Δ4-androstenedione (Adione), testosterone (T), calculated free testosterone (fT), free androgen index (FAI) and selected ratios in 1798 serum samples from healthy children, adolescents and young adults was evaluated. Samples were analyzed by Turboflow-LC-MS/MS. Sex hormone-binding globulin was analyzed by immunoassay. All steroid metabolite concentrations were positively associated with age and pubertal development in both sexes and generally higher in males than in females except for Adione. The pubertal rise in T in males was more pronounced compared to females, reflecting contribution from the testes. Ratios between steroid metabolites varied and depended on sex and age. All ratios were lower during infancy compared to later in life. Use of oral contraceptives significantly lowered serum concentrations of all steroid metabolites, fT, FAI, the 17-OHP/Adione, the Adione/T and the DHEA/Adione ratios, but not the DHEA/DHEAS ratio. We provide reference ranges for DHEA, DHEAS, 17-OHP, Adione, T, fT, FAI and selected ratios in relation to sex, age and pubertal development. Use of oral contraceptives strongly influences adrenal steroidogenesis and should be considered when diagnosing and monitoring treatment of patients with disorders of sex development. Copyright © 2014 Elsevier B.V. All rights reserved.

Sex ratio, poverty, and concurrent partnerships among men and women in the United States: a multilevel analysis.

Science.gov (United States)

Adimora, Adaora A; Schoenbach, Victor J; Taylor, Eboni M; Khan, Maria R; Schwartz, Robert J; Miller, William C

2013-11-01

Social and economic contextual factors may promote concurrent sexual partnerships, which can accelerate population HIV transmission and are more common among African Americans than U.S. Whites. We investigated the relationship between contextual factors and concurrency. We analyzed past 12-month concurrency prevalence in the 2002 National Survey of Family Growth and its contextual database in relation to county sex ratio (among respondent's racial and ethnic group), percentage in poverty (among respondent's racial and ethnic group), and violent crime rate. Analyses examined counties with balanced (0.95-1.05 males/female) or low (poverty (OR, 1.18; 95% CI, 0.98-1.42 per 10 percentage-point increase), and higher crime rates (OR, 1.04; 95% CI, 1.00-1.09 per 1000 population/year). Notably, 99.5% of Whites and 93.7% of Hispanics, but only 7.85% of Blacks, lived in balanced sex ratio counties; about 5% of Whites, half of Hispanics, and three-fourths of Blacks resided in counties with >20% same-race poverty. The dramatic Black-White differences in contextual factors in the United States and their association with sexual concurrency could contribute to the nation's profound racial disparities in HIV infection. Copyright © 2013 Elsevier Inc. All rights reserved.

Molecular signature of epistatic selection: interrogating genetic interactions in the sex-ratio meiotic drive of Drosophila simulans.

Science.gov (United States)

Chevin, Luis-Miguel; Bastide, Héloïse; Montchamp-Moreau, Catherine; Hospital, Frédéric

2009-06-01

Fine scale analyses of signatures of selection allow assessing quantitative aspects of a species' evolutionary genetic history, such as the strength of selection on genes. When several selected loci lie in the same genomic region, their epistatic interactions may also be investigated. Here, we study how the neutral polymorphism pattern was shaped by two close recombining loci that cause 'sex-ratio' meiotic drive in Drosophila simulans, as an example of strong selection with potentially strong epistasis. We compare the polymorphism data observed in a natural population with the results of forward stochastic simulations under several contexts of epistasis between the candidate loci for the drive. We compute the likelihood of different possible scenarios, in order to determine which configuration is most consistent with the data. Our results highlight that fine scale analyses of well-chosen candidate genomic regions provide information-rich data that can be used to investigate the genotype-phenotype-fitness map, which can hardly be studied in genome-wide analyses. We also emphasize that initial conditions and time of observation (here, time after the interruption of a partial selective sweep) are crucial parameters in the interpretation of real data, while these are often overlooked in theoretical studies.

Timing of first sex before marriage and its correlates: evidence from India.

Science.gov (United States)

Santhya, K G; Acharya, Rajib; Jejeebhoy, Shireen J; Ram, Usha

2011-03-01

While several studies have documented the extent of pre-marital sexual experience among young people in India, little work has been done to explore the factors that are correlated with the timing of pre-marital sexual initiation. This paper examines age at initiation of pre-marital sex, circumstances in which first sex was experienced, nature of first sexual experience and correlates of age at initiation of pre-marital sex. Life table estimates suggest that pre-marital sexual initiation occurred in adolescence for 1 in 20 young women and 1 in 10 young men. For the majority of these young people, their first sex was with an opposite-sex romantic partner. First sex, moreover, was unprotected for the majority and forced for sizeable proportion of young women. A number of individual, family-, peer- and community-level factors were correlated with age at first pre-marital sex. Moreover, considerable gender differences were apparent in the correlates of age at first pre-marital sex, with peer- and parent-level factors found more often to be significant for young women than men.

Risk of sex-specific cancers in opposite-sex and same-sex twins in Denmark and Sweden

DEFF Research Database (Denmark)

Ahrenfeldt, Linda Juel; Skytthe, Axel; Möller, Sören

2015-01-01

-scale prospective twin study compared opposite-sex (OS) and same-sex (SS) twins to test the impact of intrauterine exposures on cancer risk. Based on the Danish and Swedish twin and cancer registries, we calculated incidence rate ratios for OS and SS twins while standardized incidence ratios (SIRs) with 95......% confidence intervals (CIs) were calculated for OS/SS twins compared with the general population. RESULTS: A total of 18,001 cancers were identified during 1943-2009. No significant differences were observed between OS and SS twins, neither for the sex-specific cancers nor for cancer at all sites. All...... to prenatal testosterone - does not increase the risk of sex-specific cancers in OS females. Furthermore, the study supports that twinning per se is not a risk factor of cancer. IMPACT: Findings are reassuring as they fail to provide evidence for the hypothesis that endocrine or other difference...

A simple analytical model for dynamics of time-varying target leverage ratios

Science.gov (United States)

Lo, C. F.; Hui, C. H.

2012-03-01

In this paper we have formulated a simple theoretical model for the dynamics of the time-varying target leverage ratio of a firm under some assumptions based upon empirical observations. In our theoretical model the time evolution of the target leverage ratio of a firm can be derived self-consistently from a set of coupled Ito's stochastic differential equations governing the leverage ratios of an ensemble of firms by the nonlinear Fokker-Planck equation approach. The theoretically derived time paths of the target leverage ratio bear great resemblance to those used in the time-dependent stationary-leverage (TDSL) model [Hui et al., Int. Rev. Financ. Analy. 15, 220 (2006)]. Thus, our simple model is able to provide a theoretical foundation for the selected time paths of the target leverage ratio in the TDSL model. We also examine how the pace of the adjustment of a firm's target ratio, the volatility of the leverage ratio and the current leverage ratio affect the dynamics of the time-varying target leverage ratio. Hence, with the proposed dynamics of the time-dependent target leverage ratio, the TDSL model can be readily applied to generate the default probabilities of individual firms and to assess the default risk of the firms.

Birth order and sibling sex ratio of children and adolescents referred to a gender identity service.

Science.gov (United States)

Vanderlaan, Doug P; Blanchard, Ray; Wood, Hayley; Zucker, Kenneth J

2014-01-01

In adult male samples, homosexuality is associated with a preponderance of older brothers (i.e., the fraternal birth order effect). In several studies comparing gender dysphoric youth, who are likely to be homosexual in adulthood, to clinical or non-clinical control groups, the findings have been consistent with the fraternal birth order effect in males; however, less is known about unique sibship characteristics of gender dysphoric females. The current study investigated birth order and sibling sex ratio in a large sample of children and adolescents referred to the same Gender Identity Service (N = 768). Probands were classified as heterosexual males, homosexual males, or homosexual females based on clinical diagnostic information. Groups differed significantly in age and sibship size, and homosexual females were significantly more likely to be only children. Subsequent analyses controlled for age and for sibship size. Compared to heterosexual males, homosexual males had a significant preponderance of older brothers and homosexual females had a significant preponderance of older sisters. Similarly, the older sibling sex ratio of homosexual males showed a significant excess of brothers whereas that of homosexual females showed a significant excess of sisters. Like previous studies of gender dysphoric youth and adults, these findings were consistent with the fraternal birth order effect. In addition, the greater frequency of only children and elevated numbers of older sisters among the homosexual female group adds to a small literature on sibship characteristics of potential relevance to the development of gender identity and sexual orientation in females.

Sexual orientation, handedness, sex ratio and fetomaternal tolerance-rejection

Directory of Open Access Journals (Sweden)

Carlos Y Valenzuela

2010-01-01

Full Text Available Fraternal birth order (FBO appears as a prenatal cause of 15% of homosexual males (gays through mnemonic maternal anti-male factors. Non-right-handed men seem to be protected from homosexuality. Four hypotheses are proposed: (1 androgenic factors of non-right-handedness neutralize anti-male factors; (2 non-right-handedness and homosexuality are lethal or produce mental impairment; (3 non-right-handed male embryos are insensitive to anti-male factors; (4 mothers of non-right-handed fetuses do not produce anti-male factors. Studies of the sex ratio (SR of older and younger siblings show: (1 a significant heterogeneity in the SR of siblings of right or non-right handed heterosexual men and women; (2 lesbians are born among siblings with high SR; (3 siblings of right-handed gays show a higher SR than non-right-handed gays that present a low SR. Based on our discovery of maternal tolerance-rejection processes, associated with genetic systems (ABO, Rh, where zygotes or embryos different from their mother induce better pregnancy and maternal tolerance than do those that share antigens with their mothers, I propose a new explanation for sexual relationships, sexual orientation, handedness and sibling SR. Lesbian embryos could induce tolerance from mothers with anti-female factors. Non-right-handedness could induce maternal tolerance, or change the maternal compatibility of "gay" embryos. Alternatively, gay embryos could be poor inducers of maternal tolerance towards male traits.

Sexual orientation, handedness, sex ratio and fetomaternal tolerance-rejection.

Science.gov (United States)

Valenzuela, Carlos Y

2010-01-01

Fraternal birth order (FBO) appears as a prenatal cause of 15% of homosexual males (gays) through mnemonic maternal anti-male factors. Non-right-handed men seem to be protected from homosexuality. Four hypotheses are proposed: (1) androgenic factors of non-right-handedness neutralize anti-male factors; (2) non-right-handedness and homosexuality are lethal or produce mental impairment; (3) non-right-handed male embryos are insensitive to anti-male factors; (4) mothers of non-right-handed fetuses do not produce anti-male factors. Studies of the sex ratio (SR) of older and younger siblings show: (1) a significant heterogeneity in the SR of siblings of right or non-right handed heterosexual men and women; (2) lesbians are born among siblings with high SR; (3) siblings of right-handed gays show a higher SR than non-right-handed gays that present a low SR. Based on our discovery of maternal tolerance-rejection processes, associated with genetic systems (ABO, Rh), where zygotes or embryos different from their mother induce better pregnancy and maternal tolerance than do those that share antigens with their mothers, I propose a new explanation for sexual relationships, sexual orientation, handedness and sibling SR. Lesbian embryos could induce tolerance from mothers with anti-female factors. Non-right-handedness could induce maternal tolerance, or change the maternal compatibility of "gay" embryos. Alternatively, gay embryos could be poor inducers of maternal tolerance towards male traits.

Sex assignment of lake sturgeon (Acipenser fluvescens) based on plasma sex hormone and vitellogenin levels

Science.gov (United States)

Craig, J.M.; Papoulias, D.M.; Thomas, M.V.; Annis, M.L.; Boase, J.

2009-01-01

This study focused on identifying the sex of lake sturgeon by measuring the sex hormones estradiol and testosterone, and the phosphoprotein vitellogenin (Vtg) in blood plasma by radioimmunoassay and enzyme-linked immunosorbent assay, respectively, and evaluating these techniques as tools in lake sturgeon population management. Surveys of the St Clair River (SCR) lake sturgeon population have characterized it as rebounding by having steady or increasing recruitment since 1997. However, researchers have not been able to effectively determine the sex for most of the sturgeon they capture because few fish caught during surveys are releasing gametes. A total of 115 fish were sampled from May through June in 2004 and 2005 from the SCR, Michigan, USA. Of these, only four females and eight males were verified (i.e. they were releasing gametes at time of capture), resulting in very few fish with which to validate blood hormone and Vtg biomarkers of sex. Fifty-six percent of the fish were assigned a sex designation based on biomarker criteria. Correspondence between actual gonadal sex and biomarker-directed classification was good for the small subset of fish for which gonadal sex was definitively determined. Moreover, application of the steroid values in a predictive sex assignment model developed for white sturgeon misclassified only the same two fish that were misclassified with the steroid and Vtg biomarkers. The experimental results suggest a sex ratio of 1 : 2.7 (F:M), however more conclusive methods are needed to confirm this ratio because so few fish were available for sex validation. Of the 43 males, 14 were within the legal slot limit, 11 were smaller than 1067 mm total length (TL), and 18 were larger than 1270 mm TL. All 15 females were larger than 1270 mm TL, and thus protected by the slot limit criteria. Considering that lake sturgeon are threatened in Michigan, an advantage to using blood plasma assays was that fish were not harmed, and sample collection was

Sex-ratio, seasonality and long-term variation in maturation and spawning of the brown shrimp Crangon crangon (L.) in the German Bight (North Sea)

Science.gov (United States)

Siegel, V.; Damm, U.; Neudecker, T.

2008-12-01

Aspects of the reproductive and maturation biology of the brown shrimp Crangon crangon (L.) were studied in various subareas of the German Bight (North Sea). The size-specific sex ratio of C. crangon was examined based on length frequency distribution data. The sex ratio for the smallest size groups at which sex was determined was typically around 0.5, indicating an even ratio between males and females. The proportion of females decreased in the 30-45 mm size range. In length classes larger than 50 mm, the proportion of females constantly increases to 100% at around 60 mm total length. We concluded that sex reversal from male to female may not occur in C. crangon. Size at sexual maturity was determined from the proportion of ovigerous females. Size at maturity ( L 50) was estimated as 55.4 and 62.0 mm total length for spring and winter data, respectively. The seasonal spawning cycle was studied over the period 1958-2005. Between mid February and late June and for size classes larger than 65 mm ovigerous shrimps exceeded 80% and reached up to 100% of the females in the population. This period can be seen as the core spawning season. From early August to early December the proportion of ovigerous shrimps in the female population is very low. Interannual differences in the seasonal process are obvious with a dramatic decline in C. crangon reproductive success in the late 1980s. Various options are discussed for the reasons of the decline and recovery of the reproductive performance.

Birth order and sibling sex ratio of children and adolescents referred to a gender identity service.

Directory of Open Access Journals (Sweden)

Doug P Vanderlaan

Full Text Available In adult male samples, homosexuality is associated with a preponderance of older brothers (i.e., the fraternal birth order effect. In several studies comparing gender dysphoric youth, who are likely to be homosexual in adulthood, to clinical or non-clinical control groups, the findings have been consistent with the fraternal birth order effect in males; however, less is known about unique sibship characteristics of gender dysphoric females. The current study investigated birth order and sibling sex ratio in a large sample of children and adolescents referred to the same Gender Identity Service (N = 768. Probands were classified as heterosexual males, homosexual males, or homosexual females based on clinical diagnostic information. Groups differed significantly in age and sibship size, and homosexual females were significantly more likely to be only children. Subsequent analyses controlled for age and for sibship size. Compared to heterosexual males, homosexual males had a significant preponderance of older brothers and homosexual females had a significant preponderance of older sisters. Similarly, the older sibling sex ratio of homosexual males showed a significant excess of brothers whereas that of homosexual females showed a significant excess of sisters. Like previous studies of gender dysphoric youth and adults, these findings were consistent with the fraternal birth order effect. In addition, the greater frequency of only children and elevated numbers of older sisters among the homosexual female group adds to a small literature on sibship characteristics of potential relevance to the development of gender identity and sexual orientation in females.

Nonpaternity and Half-Siblingships as Objective Measures of Extramarital Sex: Mathematical Modeling and Simulations

Directory of Open Access Journals (Sweden)

Ryosuke Omori

2017-01-01

Full Text Available Background. Understanding the epidemiology of HIV and other sexually transmitted infections (STIs requires knowledge of sexual behavior, but self-reported behavior has limitations. We explored the reliability and validity of nonpaternity and half-siblings ratios as biomarkers of current and past extramarital sex. Methods. An individual-based Monte Carlo simulation model was constructed to describe partnering and conception in human populations with a focus on Sub-Saharan Africa (SSA. The model was parameterized with representative biological, behavioral, and demographic data. Results. Nonpaternity and half-siblings ratios were strongly correlated with extramarital sex, with Pearson correlation coefficients (PCC of 0.79 (95% CI: 0.71–0.86 and 0.77 (0.68–0.84, respectively. Age-specific nonpaternity ratios correlated with past extramarital sex at time of conception for different scenarios: for example, PCC, after smoothing by moving averages, was 0.75 (0.52–0.89 in a scenario of steadily decreasing nonmarital sex and 0.39 (0.01–0.73 in a scenario of transient drops in nonmarital sex. Simulations assuming self-reported levels of extramarital sex from Kenya yielded nonpaternity levels lower than global nonpaternity data, suggesting sizable underreporting of extramarital sex. Conclusions. Nonpaternity and half-siblings ratios are useful objective measures of extramarital sex that avoid limitations in self-reported sexual behavior.

Sex selection: treating different cases differently.

Science.gov (United States)

Dickens, B M; Serour, G I; Cook, R J; Qiu, R-Z

2005-08-01

This paper contrasts ethical approaches to sex selection in countries where discrimination against women is pervasive, resulting in selection against girl children, and in countries where there is less general discrimination and couples do not prefer children of either sex. National sex ratio imbalances where discrimination against women is common have resulted in laws and policies, such as in India and China, to deter and prevent sex selection. Birth ratios of children can be affected by techniques of prenatal sex determination and abortion, preconception sex selection and discarding disfavored embryos, and prefertilization sperm sorting, when disfavored sperm remain unused. Incentives for son preference are reviewed, and laws and policies to prevent sex selection are explained. The elimination of social, economic and other discrimination against women is urged to redress sex selection against girl children. Where there is no general selection against girl children, sex selection can be allowed to assist families that want children of both sexes.

Population and colony-level determinants of tertiary sex ratio in the declining barn swallow.

Directory of Open Access Journals (Sweden)

Nicola Saino

Full Text Available Sex ratio of adults (tertiary sex ratio, TSR is a major feature of animal populations with consequences for their behaviour, genetic structure and viability. Spatial and temporal variation in TSR occurs within species but the mechanisms behind it are poorly understood. In this long-term study of a declining population of a socially monogamous, colonial, migratory bird, the barn swallow (Hirundo rustica, we first analyzed population-level variation in TSR ( =  proportion of males of yearlings at sexual maturation in relation to ecological conditions as gauged by annual survival rate of adults. TSR was male-biased both among yearlings and older individuals, but male bias of yearlings was more pronounced after years with larger decline in adult survival. Thus, male offspring were less susceptible to the adverse ecological conditions that cause increased mortality. Dispersal and settling site decisions can have major consequences on fitness via the effects of local TSR on mating and sperm competition. Breeding barn swallows are highly philopatric while natal dispersal is high and, together with mortality, is the main determinant of colony TSR. We thus also investigated the mechanisms of breeding colony choice by yearlings and found that TSR of new-settlers in a given colony and year was negatively predicted by TSR of returning, early arriving older individuals in that year, but not by overall TSR at the colony in the previous year. This suggests that in our male-biased population new-settler males respond to local TSR upon arrival to choose the sites with larger breeding opportunities. Hence, variation in ecological conditions as reflected by adult survival can shift the TSR of individuals recruiting into a local population, with potentially various demographic consequences. However, breeding site choice based on TSR tends to homogenize TSR at a population level likely by facilitating settling of dispersing males in colonies with less male

Education and gender bias in the sex ratio at birth: evidence from India.

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Echávarri, Rebeca A; Ezcurra, Roberto

2010-02-01

This article investigates the possible existence of a nonlinear link between female disadvantage in natality and education. To this end, we devise a theoretical model based on the key role of social interaction in explaining people's acquisition of preferences, which justifies the existence of a nonmonotonic relationship between female disadvantage in natality and education. The empirical validity of the proposed model is examined for the case of India, using district-level data. In this context, our econometric analysis pays particular attention to the role of spatial dependence to avoid any potential problems of misspecification. The results confirm that the relationship between the sex ratio at birth and education in India follows an inverted U-shape. This finding is robust to the inclusion of additional explanatory variables in the analysis, and to the choice of the spatial weight matrix used to quantify the spatial interdependence between the sample districts.

The effects of sex, sexual orientation, and digit ratio (2D:4D) on mental rotation performance.

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Peters, Michael; Manning, John T; Reimers, Stian

2007-04-01

In spite of the reduced level of experimental control, this large scale study brought some clarity into the relation between mental rotation task (MRT) performance and a number of variables where contradictory associations had previously been reported in the literature. Clear sex differences in MRT were observed for a sample of 134,317 men and 120,783 women, with men outperforming women. There were also MRT differences as a function of sexual orientation: heterosexual men performed better than homosexual men and homosexual women performed better than heterosexual women. Although bisexual men performed better than homosexual men but less well than heterosexual men, no significant differences were observed between bisexual and homosexual women. MRT performance in both men and women peaked in the 20-30 year range, and declined significantly and markedly thereafter. Both men and women showed a significant negative correlation between left and right digit finger ratio and MRT scores, such that individuals with smaller digit ratios (relatively longer ring finger than index finger) performed better than individuals with larger digit ratios.

Estrogenic exposure affects metamorphosis and alters sex ratios in the northern leopard frog (Rana pipiens): identifying critically vulnerable periods of development.

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Hogan, Natacha S; Duarte, Paula; Wade, Michael G; Lean, David R S; Trudeau, Vance L

2008-05-01

During the transformation from larval tadpole to juvenile frog, there are critical periods of metamorphic development and sex differentiation that may be particularly sensitive to endocrine disruption. The aim of the present study was to identify sensitive developmental periods for estrogenic endocrine disruption in the northern leopard frog (Rana pipiens) using short, targeted exposures to the synthetic estrogen, ethinylestradiol (EE2). Post-hatch tadpoles (Gosner stage 27) were exposed over five distinct periods of metamorphosis: early (stage 27-30), mid (stage 30-36), early and mid (stage 27-36), late (stage 36-42), and the entire metamorphic period (chronic; stage 27-42). For each period, animals were sampled immediately following the EE2 exposure and at metamorphic climax (stage 42). The effects of EE2 on metamorphic development and sex differentiation were assessed through measures of length, weight, developmental stage, days to metamorphosis, sex ratios and incidence of gonadal intersex. Our results show that tadpoles exposed to EE2 during mid-metamorphosis were developmentally delayed immediately following exposure and took 2 weeks longer to reach metamorphic climax. In the unexposed groups, there was low proportion (0.15) of intersex tadpoles at stage 30 and gonads appeared to be morphologically distinct (male and female) in all individuals by stage 36. Tadpoles exposed early in development displayed a strong female-biased sex ratio compared to the controls. Moreover, these effects were also seen at metamorphic climax, approximately 2-3 months after the exposure period, demonstrating that transient early life-stage exposure to estrogen can induce effects on the reproductive organs that persist into the beginning of adult life-stages.

Sex, age, pubertal development and use of oral contraceptives in relation to serum concentrations of DHEA, DHEAS, 17α-hydroxyprogesterone, Δ4-androstenedione, testosterone and their ratios in children, adolescents and young adults

DEFF Research Database (Denmark)

Søeborg, Tue; Frederiksen, Hanne; Mouritsen, Annette

2014-01-01

The influence of sex, age, pubertal development and oral contraceptives on dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), 17α-hydroxyprogesterone (17-OHP), Δ4-androstenedione (Adione), testosterone (T), calculated free testosterone (fT), free androgen index (FAI) and selected ratios in 1798...... serum samples from healthy children, adolescents and young adults was evaluated. Samples were analyzed by Turboflow-LC-MS/MS. Sex hormone-binding globulin was analyzed by immunoassay. All steroid metabolite concentrations were positively associated with age and pubertal development in both sexes....... Use of oral contraceptives significantly lowered serum concentrations of all steroid metabolites, fT, FAI, the 17-OHP/Adione, the Adione/T and the DHEA/Adione ratios, but not the DHEA/DHEAS ratio. We provide reference ranges for DHEA, DHEAS, 17-OHP, Adione, T, fT, FAI and selected ratios in relation...

Quantitative sexing (Q-Sexing) and relative quantitative sexing (RQ ...

African Journals Online (AJOL)

samer

Key words: Polymerase chain reaction (PCR), quantitative real time polymerase chain reaction (qPCR), quantitative sexing, Siberian tiger. INTRODUCTION. Animal molecular sexing .... 43:3-12. Ellegren H (1996). First gene on the avian W chromosome (CHD) provides a tag for universal sexing of non-ratite birds. Proc.

Laboratory studies on insecticide resistance, alcohol tolerance and sex ratio distortion by meiotic drive in the Mediterranean fruit fly, Ceratitis capitata (Wied.)

International Nuclear Information System (INIS)

Wood, R.J.

1990-01-01

Three approaches to developing a genetic sexing technique for the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), are discussed. Laboratory studies in late third instar larvae of the medfly revealed a potential for dieldrin resistance. A programme of sib selection produced the DiR strain, more than 60x resistante to dieldrin with cross-resistance to other cyclodienes, HCH, malathion and permethrin. Adults were not resistant. Crosses showed dieldrin resistance to be monofactorial, subject to a modifying effect from the genetic background on the expression of the homozygote. The 'backcrossing with selection' technique was used to separate dieldrin and malathion resistance but, in the process, resistance to both insecticides was lost after four to eight generations. Attempts to induce male linkage of the R gene by X irradiation were unsuccessful. Further genetic studies on resistance are recommended. With a view to producing an ethanol sensitive strain homozygous for an ADH null mutation (Adh - /Adh - ), pentenol selection of late third instar larvae was carried out, combined with ethyl methane sulphonate (EMS) treatments of adults. This produced a maximum of 15x tolerance of pentenol but no associated change in ethanol tolerance. Electrophoresis (PAGE) showed that two major ADH systems were at their most active in late third instar larvae. A gene causing a male distorted sex ratio in the progeny of males carrying it was isolated after X irradiation. The expression of the gene, which appears to be an example of meiotic drive, was enhanced by reducing the ambient temperature of parent flies from 26 deg. C+-2.0 to 18 deg. C+-1.5 during days 2-5 of pupal development. Selection to increase the expression of the gene produced families with less than 20% females but sex ratio tended to revert towards normal in subsequent generations. A potential is seen for producing strains in which sex ratio can be regulated by temperature. (author). 30 refs, 5 figs, 2

A cohort study of the association between secondary sex ratio and parental exposure to polybrominated biphenyl (PBB and polychlorinated biphenyl (PCB

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Terrell Metrecia L

2009-08-01

Full Text Available Abstract Background Polybrominated biphenyl (PBB, a brominated flame retardant, was accidently mixed into animal feed in Michigan (1973–1974 resulting in human exposure through consumption of contaminated meat, milk and eggs. Beginning in 1976 individuals who consumed contaminated products were enrolled in the Michigan Long-Term PBB Study. This cohort presents a unique opportunity to study the association between parental exposures to PBB and offspring sex ratio. Methods We identified offspring of female PBB cohort participants (born 1975–1988 and obtained electronic birth records for those born in the state of Michigan. We linked this information to parental serum PBB and PCB concentrations collected at enrollment into the cohort. We modeled the odds of a male birth with generalized estimating equations accounting for the non-independence of siblings born to the same parents. We explored potential confounders: parental age and education at offspring's birth, parental body mass index at cohort enrollment, birth order, gestational age and year of offspring's birth. Results The overall proportion of male offspring among 865 live births to cohort mothers was 0.542. This was higher than the national male proportion of 0.514 (binomial test: p = 0.10. When both parents were in the cohort (n = 300, we found increased odds of a male birth with combined parents' enrollment PBB exposure ≥ the median concentrations (3 μg/L for mothers; 6 μg/L for fathers compared to combined parents' PBB exposure Conclusion This study adds to the body of literature on secondary sex ratio and exposure to environmental contaminants. In this population, combined parental exposure to PBBs or PCBs increased the odds of a male birth. Further research is needed to corroborate these findings and shed light on the biological mechanisms by which these types of chemicals may influence the secondary sex ratio.

Sex ratio at birth: scenario from normal- and high-level natural radiation areas of Kerala coast in south-west India

International Nuclear Information System (INIS)

Koya, P.K.M.; Jaikrishan, G.; Sudheer, K.R.; Madhusoodhanan, M.; Jagadeesan, C.K.; Das, Birajalaxmi; Andrews, V.J.

2015-01-01

Newborns were monitored for congenital malformations in four government hospitals located in high-level (ambient dose >1.5 mGy/year) and normal-level (≤1.5 mGy/year) natural radiation areas of Kerala, India, from August 1995 to December 2012. Sex ratio at birth (SRB) among live singleton newborns and among previous children, if any, of their mothers without history of any abortion, stillbirth or twins is reported here. In the absence of environmental stress or selective abortion of females, global average of SRB is about 1050 males to 1000 females. A total of 151,478 singleton, 1031 twins, 12 triplets and 1 quadruplet deliveries were monitored during the study period. Sex ratio among live singleton newborns was 1046 males (95 % CI 1036-1057) for 1000 females (77,153 males:73,730 females) and was comparable to the global average. It was similar in high-level and normal-level radiation areas of Kerala with SRB of 1050 and 1041, respectively. It was consistently more than 1000 and had no association with background radiation levels, maternal and paternal age at birth, parental age difference, gravida status, ethnicity, consanguinity or year of birth. Analysis of SRB of the children of 139,556 women whose reproductive histories were available suggested that couples having male child were likely to opt for more children and this, together with enhanced rate of males at all birth order, was skewing the overall SRB in favour of male children. Though preference for male child was apparent, extreme steps of sex-selective abortion or infanticide were not prevalent. (orig.)

Sex ratio at birth: scenario from normal- and high-level natural radiation areas of Kerala coast in south-west India

Energy Technology Data Exchange (ETDEWEB)

Koya, P.K.M.; Jaikrishan, G.; Sudheer, K.R. [Bhabha Atomic Research Centre, Low Level Radiation Research Laboratory, Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Kollam (India); Madhusoodhanan, M. [Victoria Hospital, Department of Paediatrics, Kollam (India); Jagadeesan, C.K. [Directorate of Health Services, Thiruvananthapuram (India); Das, Birajalaxmi [Bhabha Atomic Research Centre, Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Mumbai (India); Andrews, V.J.

2015-11-15

Newborns were monitored for congenital malformations in four government hospitals located in high-level (ambient dose >1.5 mGy/year) and normal-level (≤1.5 mGy/year) natural radiation areas of Kerala, India, from August 1995 to December 2012. Sex ratio at birth (SRB) among live singleton newborns and among previous children, if any, of their mothers without history of any abortion, stillbirth or twins is reported here. In the absence of environmental stress or selective abortion of females, global average of SRB is about 1050 males to 1000 females. A total of 151,478 singleton, 1031 twins, 12 triplets and 1 quadruplet deliveries were monitored during the study period. Sex ratio among live singleton newborns was 1046 males (95 % CI 1036-1057) for 1000 females (77,153 males:73,730 females) and was comparable to the global average. It was similar in high-level and normal-level radiation areas of Kerala with SRB of 1050 and 1041, respectively. It was consistently more than 1000 and had no association with background radiation levels, maternal and paternal age at birth, parental age difference, gravida status, ethnicity, consanguinity or year of birth. Analysis of SRB of the children of 139,556 women whose reproductive histories were available suggested that couples having male child were likely to opt for more children and this, together with enhanced rate of males at all birth order, was skewing the overall SRB in favour of male children. Though preference for male child was apparent, extreme steps of sex-selective abortion or infanticide were not prevalent. (orig.)

Climate change is associated with male:female ratios of fetal deaths and newborn infants in Japan

DEFF Research Database (Denmark)

Fukuda, Misao; Fukuda, Kiyomi; Shimizu, Takashi

2014-01-01

. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Yearly sex ratios of fetal deaths and newborn infants and monthly fetal death rates and sex ratios of newborn infants. RESULT(S): A statistically significant positive association was found between yearly temperature differences and sex ratios of fetal deaths......; a statistically significant negative association was found between temperature differences and sex ratios of newborn infants from 1968 to 2012, and between sex ratios of births and of fetal deaths. The sex ratios of fetal deaths have been increasing steadily along with temperature differences, whereas the sex......OBJECTIVE: To evaluate whether climate change is associated with male:female ratios (sex ratios) of fetal deaths and births in Japan. DESIGN: A population-based cohort study. SETTING: Not applicable. PATIENT(S): Newborn infants and fetuses spontaneously aborted after 12 weeks of gestation...

Repeated in utero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure affects male gonads in offspring, leading to sex ratio changes in F2 progeny

International Nuclear Information System (INIS)

Ikeda, Masahiko; Tamura, Masashi; Yamashita, Junko; Suzuki, Chinatsu; Tomita, Takako

2005-01-01

The effects of in utero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the reproductive system of male rat offspring (F 1 ) and the sex ratio of the subsequent generation (F 2 ) were examined. Female Holtzman rats were gavaged with an initial loading dose of 400 ng/kg TCDD prior to mating, followed by weekly maintenance doses of 80 ng/kg during mating, pregnancy, and the lactation period. Maternal exposure to TCDD had no significant effects on fetus/pup (F 1 ) mortality, litter size, or sex ratio on gestation day (GD) 20 or postnatal day (PND) 2. The TCDD concentration in maternal livers and adipose tissue on GD20 was 1.21 and 1.81 ng/kg, respectively, and decreased at weaning to 0.72 in the liver and 0.84 in the adipose tissue. In contrast, the TCDD concentration in pup livers was 1.32 ng/kg on PND2 and increased to 1.80 ng/kg at weaning. Ventral prostate weight of male offspring was significantly decreased by TCDD exposure on PND28 and 120 compared with that of controls. Weight of the testes, cauda epididymides, and seminal vesicle, and sperm number in the cauda epididymis were not changed by TCDD exposure at PND120. TCDD- or vehicle-exposed male offspring were mated with unexposed females. The sex ratio (percentage of male pups) of F 2 offspring was significantly reduced in the TCDD-exposed group compared with controls. These results suggest that in utero and lactational TCDD exposures affect the development of male gonads in offspring (F 1 ), leading to changes in the sex ratio of the subsequent generation (F 2 )

A Hybrid Joint Moment Ratio Test for Financial Time Series

NARCIS (Netherlands)

P.A. Groenendijk (Patrick); A. Lucas (André); C.G. de Vries (Casper)

1998-01-01

textabstractWe advocate the use of absolute moment ratio statistics in conjunction with standard variance ratio statistics in order to disentangle linear dependence, non-linear dependence, and leptokurtosis in financial time series. Both statistics are computed for multiple return horizons

RECENT TRENDS IN GENDER RATIO AT BIRTH IN HANGZHOU, CHINA.

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Tang, L; Qiu, L Q; Yau, Kkw; Hui, Y V; Binns, C W; Lee, A H

2015-12-01

Higher than normal sex ratios at birth in China have been reported since the early 1980's. This study aimed to investigate recent trends in sex ratio at birth in Hangzhou, capital of Zhejiang Province in southeast China. Information on selected maternal and birth-related characteristics was extracted from the Hangzhou Birth Information Database for all pregnant women who delivered live births during 2005-2014. The sex ratios at birth were calculated after excluding infants with missing data on gender and those born with ambiguous genitalia. A total of 478,192 male births and 430,852 female births were recorded giving an overall ratio of 111.0. The sex ratio at birth was almost constant at around 110.7 during the period 2005-2008, followed by an increase to the peak at 113.1 in 2010 and then declined back to 109.6 in 2014. The gender ratio at birth in Hangzhou remained unbalanced for the past decade.

Seed sexing revealed female bias in two Rumex species

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Dagmara Kwolek

2011-07-01

Full Text Available Sex-ratio bias in seeds of dioecious Rumex species with sex chromosomes is an interesting and still unsettled issue. To resolve gender among seeds of R. acetosa and R. thyrsiflorus (two species with an XX/XY1Y2 sex chromosome system, this work applied a PCR-based method involving DNA markers located on Y chromosomes. Both species showed female-biased primary sex ratios, with female bias greater in R. acetosa than in R. thyrsiflorus. The observed predominance of female seeds is consistent with the view that the female biased sex ratios in Rumex are conditioned not only postzygotically but also prezygotically.

Links between sex-typed time use in middle childhood and gender development in early adolescence.

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McHale, Susan M; Kim, Ji-Yeon; Whiteman, Shawn; Crouter, Ann C

2004-09-01

The authors studied sex-typing in the kinds (e.g., sports, handicrafts) and social contexts (same- vs. other-sex companions) of children's free time activities, and the links between sex-typed activities and gender development over 2 years. Participants were 200 White, working- and middle-class children (103 girls, 97 boys; mean age = 10.86 years). In annual home interviews, children rated their self-esteem, gender role attitudes and sex-typed personality qualities, academic interests, and school grades. During 7 nightly phone interviews each year, children reported on their activities. Boys were more sex-typed than girls in their peer activities, and children were least sex-typed in their activities with siblings. Sex-typed activities in middle childhood predicted individual differences in gender development in early adolescence. Copyright 2004 American Psychological Association

Ratio-based lengths of intervals to improve fuzzy time series forecasting.

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Huarng, Kunhuang; Yu, Tiffany Hui-Kuang

2006-04-01

The objective of this study is to explore ways of determining the useful lengths of intervals in fuzzy time series. It is suggested that ratios, instead of equal lengths of intervals, can more properly represent the intervals among observations. Ratio-based lengths of intervals are, therefore, proposed to improve fuzzy time series forecasting. Algebraic growth data, such as enrollments and the stock index, and exponential growth data, such as inventory demand, are chosen as the forecasting targets, before forecasting based on the various lengths of intervals is performed. Furthermore, sensitivity analyses are also carried out for various percentiles. The ratio-based lengths of intervals are found to outperform the effective lengths of intervals, as well as the arbitrary ones in regard to the different statistical measures. The empirical analysis suggests that the ratio-based lengths of intervals can also be used to improve fuzzy time series forecasting.

Time to unsafe sexual practice among cross-border female sex workers in Metemma Yohannes, North West Ethiopia.

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Gezie, Lemma Derseh; Taye, Belaynew Wassie; Ayele, Tadesse Awoke

2015-07-28

Because of the nature of their work, female sex workers are at risk of sexually transmitted diseases. Cross-border areas are places where this situation becomes worse. In Ethiopia, there has been a serious scarcity of studies on the time at which unsafe sexual practice starts and on factors which determine the practice among female sex workers there. Therefore, this study aimed to fill this identified gap. A total of 467 women who had been sex workers at least for three months prior to the resumption of the study were included. A structured and pre-tested questionnaire was used to collect data from July-August, 2010. Descriptive statistics was used to explore the data, and the Extended Cox-Regression model was employed to identify the predictors of time-to-unsafe sexual practice. The study participants were followed for 6, 643 person-months. The overall incidence density of unsafe sexual practice was 44.71 persons per 1000 persons-months. The hazard of unsafe sexual practice increased by 3.0 % every month (p-value =0.040) due to problem-drinking. Those female sex workers with familiarized clients had a two-fold hazard of practicing unsafe sex compared to their counterparts (AHR = 1.94 95 % CI 1.49, 2.53). The predominant sexual client type and the work place of sex workers were the other significant predictors of unsafe sexual practice. The incidence of unsafe sexual practice was found to be high among sex workers in the cross-border area. Time-to-unsafe sexual practice was significantly associated with female sex workers' status of familiarity with their clients, predominant sexual client type, their work place, and the interaction term of time and problem-drinking. Interventions need to be made on these controllable social and behavioral characteristics to help sex workers extend the duration of their safe sexual practice beyond the time they will quit sex work.

EFFECT OF TIMING OF ARTIFICIAL INSEMINATION ON THE FERTILITY AND SEX RATIO IN NELORE HEIFERS INFLUÊNCIA DO MOMENTO DA INSEMINAÇÃO ARTIFICIAL SOBRE A FERTILIDADE E O SEXO DA CRIA DE NOVILHAS DA RAÇA NELORE

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José Ricardo Almeida de Andrade

2008-12-01

Full Text Available The aim of this study was to evaluate the effect of timing of artificial insemination on the fertility and calf sex ratio in Nelore heifers (n = 200 submitted a protocol of timed artificial insemination (TAI.  The heifers, distributed into five groups (GC, GT6, GT12, GT18 and GT24, presented a mean of 2.5 years old and 342 Kg of body weight. The inseminations were performed in the moments 0 (GC, 6 (GT6, 12 (GT12, 18 (GT18 and 24 (GT24 hours after the injection of GnRH. The conception rates were 87.5% (GC, 82.5% (GT6, 77.5% (GT12, 85.0% (GT18 and 77.5% (GT24. There was no statistical difference (p>0.05 in the conception rates between the five treatments. The percentage of calved males was 38.2% (GC, 48.5% (GT6, 45.2% (GT12, 55.9% (GT18 and 58.6% (GT24. The male/female ratio was 0.62 (GC, 0.94 (GT6, 0.82 (GT12, 1.27 (GT18 and 1.42 (GT24. Statistical difference was found (p<0.05 in the male/female ratio between the five treatments. The timing of artificial insemination has influence on the sex ratio, showing an increase in the proportion of calved males when the insemination is progressively delayed. Within of the measured interval of time (0-24h after GnRH, the fertility of Nelore heifers is not influenced by the moment of the artificial insemination.

KEY WORDS: Beef cattle, management, pregnancy test, ultrasound, sexing. Objetivou-se avaliar o efeito do momento da inseminação artificial (IA sobre a fertilidade e a proporção do sexo da cria de novilhas da raça Nelore (n = 200 submetidas a protocolo de IATF. As novilhas, distribuídas em cinco tratamentos (GC, GT6, GT12, GT18 e GT24, apresentavam idade média de 2,5 anos e peso médio de 342 kg. Realizaram-se as inseminações nos momentos 0 (GC, 6 (GT6, 12 (GT12, 18 (GT18 e 24 (GT24 horas após a aplicação do GnRH. As taxas de concepção foram de 87,5% (GC, 82,5% (GT6, 77,5% (GT12, 85,0% (GT18 e de 77,5% (GT24. Não houve diferença estatística (p>0,05 entre as taxas de

Sex chromosome repeats tip the balance towards speciation.

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O'Neill, Michael J; O'Neill, Rachel J

2018-04-06

Because sex chromosomes, by definition, carry genes that determine sex, mutations that alter their structural and functional stability can have immediate consequences for the individual by reducing fertility, but also for a species by altering the sex ratio. Moreover, the sex-specific segregation patterns of heteromorphic sex chromosomes make them havens for selfish genetic elements that not only create sub-optimal sex ratios, but can also foster sexual antagonism. Compensatory mutations to mitigate antagonism or return sex ratios to a Fisherian optimum can create hybrid incompatibility and establish reproductive barriers leading to species divergence. The destabilizing influence of these selfish elements is often manifest within populations as copy number variants (CNVs) in satellite repeats and transposable elements (TE) or as CNVs involving sex determining genes, or genes essential to fertility and sex chromosome dosage compensation. This review catalogs several examples of well-studied sex chromosome CNVs in Drosophilids and mammals that underlie instances of meiotic drive, hybrid incompatibility and disruptions to sex differentiation and sex chromosome dosage compensation. While it is difficult to pinpoint a direct cause/effect relationship between these sex chromosome CNVs and speciation, it is easy to see how their effects in creating imbalances between the sexes, and the compensatory mutations to restore balance, can lead to lineage splitting and species formation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Brood size and sex ratio in response to host quality and wasp traits in the gregarious parasitoid Oomyzus sokolowskii (Hymenoptera: Eulophidae

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Xianwei Li

2017-01-01

Full Text Available This laboratory study investigated whether the larval-pupal parasitoid Oomyzus sokolowskii females adjust their brood size and sex ratio in response to body size and stage of Plutella xylostella larval hosts, as well as to their own body size and the order of oviposition. These factors were analyzed using multiple regression with simultaneous entry of them and their two-way interactions. Parasitoids brood size tended to increase with host body size at parasitism when the 4th instar larval host was attacked, but did not change when the 2nd and 3rd instar larvae were attacked. Parasitoids did not vary in brood size according to their body size, but decreased with their bouts of oviposition on a linear trend from 10 offspring adults emerged per host in the first bout of oviposition down to eight in the third. Parasitoid offspring sex ratio did not change with host instar, host body weight, wasp body size, and oviposition bout. Proportions of male offspring per brood were from 11% to 13% from attacking the 2nd to 4th instar larvae and from 13% to 16% across three successive bouts of oviposition, with a large variation for smaller host larvae and wasps. When fewer than 12 offspring were emerged from a host, one male was most frequently produced; when more than 12 offspring were emerged, two or more males were produced. Our study suggests that O. sokolowskii females may optimize their clutch size in response to body size of mature P. xylostella larvae, and their sex allocation in response to clutch size.

Reproductive and behavioral aspects of red-winged tinamous (Rhynchotus rufescens in groups with different sex ratios

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VU Cromberg

2007-09-01

Full Text Available The aim of this research study was to evaluate the reproductive performance of tinamous submitted to five different male:female ratios. The study was carried out with 72 birds in a randomized experimental design with 4 replications. Tinamous were housed in cages, using the ratios of one (1:1, two (2:1, three (3:1 and four (4:1 females per male, and also one male was housed with three females individually (3R:1, in a rotational system. Reproductive records of the breeding season from September 2004 to March 2005 were used. The reproductive traits studied were: number of eggs laid, fertility, and percentage of eggs damaged and cracked by pecking. Nonparametric analyses of these traits were performed using Kruskal-Wallis test. Two replications of treatments 1:1 and 4:1, and one of treatment 2:1 were video-taped for three days, 12 hours/day. The videotapes were sampled according to the scan method to fit an ethogram. Birds were also watched for one hour per day to study dominance and agonistic behavior. None of the reproductive traits was affected by mating sex ratio (p<0.05. Female dominance could be related to displacement behavior (r=1.00, and male sitting in immobility plus sitting in activity behaviors were related to lower number of damaged eggs (r=-0.90. Social dominance was indirectly determined by displacement behavior in the study situation. A large number of damaged eggs occurred in all treatments, thereby not allowing a clear conclusion on the best male:female ratio.

Evidence of oligogenic sex determination in the apple snail Pomacea canaliculata.

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Yusa, Yoichi; Kumagai, Natsumi

2018-02-26

A small number of genes may interact to determine sex, but few such examples have been demonstrated in animals, especially through comprehensive mating experiments. The highly invasive apple snail Pomacea canaliculata is gonochoristic and shows a large variation in brood sex ratio, and the involvement of multiple genes has been suggested for this phenomenon. We conducted mating experiments to determine whether their sex determination involves a few or many genes (i.e., oligogenic or polygenic sex determination, respectively). Full-sib females or males that were born from the same parents were mated to an adult of the opposite sex, and the brood sex ratios of the parents and their offspring were investigated. Analysis of a total of 4288 offspring showed that the sex ratios of offspring from the full-sib females were variable but clustered into only a few values. Similar patterns were observed for the full-sib males, although the effect was less clear because fewer offspring were used (n = 747). Notably, the offspring sex ratios of all full-sib females in some families were nearly 0.5 (proportion of males) with little variation. These results indicate that the number of genotypes of the full-sibs, and hence genes involved in sex determination, is small in this snail. Such oligogenic systems may be a major sex-determining system among animals, especially those with variable sex ratios.

A Time-Measurement System Based on Isotopic Ratios

International Nuclear Information System (INIS)

Vo, Duc T.; Karpius, P.J.; MacArthur, D.W.; Thron, J.L.

2007-01-01

A time-measurement system can be built based on the ratio of gamma-ray peak intensities from two radioactive isotopes. The ideal system would use a parent isotope with a short half-life decaying to a long half-life daughter. The activities of the parent-daughter isotopes would be measured using a gamma-ray detector system. The time can then be determined from the ratio of the activities. The best-known candidate for such a system is the 241 Pu- 241 Am parent-daughter pair. However, this 241 Pu- 241 Am system would require a high-purity germanium detector system and sophisticated software to separate and distinguish between the many gamma-ray peaks produced by the decays of the two isotopes. An alternate system would use two different isotopes, again one with a short half-life and one with a half-life that is long relative to the other. The pair of isotopes 210 Pb and 241 Am (with half-lives of 22 and 432 years, respectively) appears suitable for such a system. This time-measurement system operates by measuring the change in the ratio of the 47-keV peak of 210 Pb to the 60-keV peak of 241 Am. For the system to work reasonably well, the resolution of the detector would need to be such that the two gamma-ray peaks are well separated so that their peak areas can be accurately determined using a simple region-of-interest (ROI) method. A variety of detectors were tested to find a suitable system for this application. The results of these tests are presented here.

Mothers adjust offspring sex to match the quality of the rearing environment.

Science.gov (United States)

Pryke, Sarah R; Rollins, Lee A

2012-10-07

Theory predicts that mothers should adjust offspring sex ratios when the expected fitness gains or rearing costs differ between sons and daughters. Recent empirical work has linked biased offspring sex ratios to environmental quality via changes in relative maternal condition. It is unclear, however, whether females can manipulate offspring sex ratios in response to environmental quality alone (i.e. independent of maternal condition). We used a balanced within-female experimental design (i.e. females bred on both low- and high-quality diets) to show that female parrot finches (Erythrura trichroa) manipulate primary offspring sex ratios to the quality of the rearing environment, and not to their own body condition and health. Individual females produced an unbiased sex ratio on high-quality diets, but over-produced sons in poor dietary conditions, even though they maintained similar condition between diet treatments. Despite the lack of sexual size dimorphism, such sex ratio adjustment is in line with predictions from sex allocation theory because nutritionally stressed foster sons were healthier, grew faster and were more likely to survive than daughters. These findings suggest that mothers may adaptively adjust offspring sex ratios to optimally match their offspring to the expected quality of the rearing environment.

Local and neighboring patch conditions alter sex-specific movement in banana weevils.

Science.gov (United States)

Carval, Dominique; Perrin, Benjamin; Duyck, Pierre-François; Tixier, Philippe

2015-12-01

Understanding the mechanisms underlying the movements and spread of a species over time and space is a major concern of ecology. Here, we assessed the effects of an individual's sex and the density and sex ratio of conspecifics in the local and neighboring environment on the movement probability of the banana weevil, Cosmopolites sordidus. In a "two patches" experiment, we used radiofrequency identification tags to study the C. sordidus movement response to patch conditions. We showed that local and neighboring densities of conspecifics affect the movement rates of individuals but that the density-dependent effect can be either positive or negative depending on the relative densities of conspecifics in local and neighboring patches. We demonstrated that sex ratio also influences the movement of C. sordidus, that is, the weevil exhibits nonfixed sex-biased movement strategies. Sex-biased movement may be the consequence of intrasexual competition for resources (i.e., oviposition sites) in females and for mates in males. We also detected a high individual variability in the propensity to move. Finally, we discuss the role of demographic stochasticity, sex-biased movement, and individual heterogeneity in movement on the colonization process.

The effects of cavity length on nest size, sex ratio and mortality of Centris (Heterocentris) analis (Hymenoptera, Apidae, Centridini)

OpenAIRE

Alonso , Juliana; Silva , Janaina; Garófalo , Carlos

2012-01-01

International audience; This study investigated the effects of different cavity lengths in trap-nests on the number of cells constructed per nest, sex ratio and mortality of offspring of Centris analis at three sites in Ribeirão Preto, São Paulo, Brazil. Cavity length did not affect the occupation rates of the trap-nests, with the exception of a preference for the shortest trap-nests found at one site. The number of cells per nest increased with trap-nest length. Cavity length affected neithe...

How Good Is Your Rule of Thumb? Validating Male-to-Female Case Ratio as a Proxy for Men Who Have Sex With Men Involvement in N. gonorrhoeae Incidence at the County Level.

Science.gov (United States)

Stenger, Mark; Bauer, Heidi; Klingler, Ellen; Bell, Teal; Donnelly, Jennifer; Eaglin, Margaret; Jespersen, Megan; Madera, Robbie; Mattson, Melanie; Torrone, Elizabeth

2018-03-01

Lacking information on men who have sex with men (MSM) for most reported cases, sexually transmitted disease (STD) programs in the United States have used crude measures such as male-to-female case ratios (MFCR) as a rule of thumb to gauge MSM involvement at the local level, primarily with respect to syphilis cases in the past. Suitability of this measure for gonorrhea incidence has not previously been investigated. A random sample of gonorrhea cases reported from January 2010 through June 2013 were interviewed in selected counties participating in the STD Surveillance Network to obtain gender of sex partners and history of transactional sex. Weighted estimates of proportion of cases among MSM and proportion reporting transactional sex were developed; correlation between MFCR and proportion MSM was assessed. Male-to-female case ratio ranged from 0.66 to 8.7, and the proportion of cases occurring among MSM varied from 2.5% to 62.3%. The MFCR was strongly correlated with proportion of cases among MSM after controlling for transactional sex (Pearson partial r = 0.754, P < 0.0001). Male-to-female case ratio for gonorrhea at the county level is a reliable proxy measure indicating MSM involvement in gonorrhea case incidence and should be used by STD programs to tailor their programmatic mix to include MSM-specific interventions.

Similarity in Chronotype and Preferred Time for Sex and Its Role in Relationship Quality and Sexual Satisfaction

Directory of Open Access Journals (Sweden)

Paulina Jocz

2018-04-01

Full Text Available Recently, the issue of diurnal preferences has been increasingly studied within the context of romantic relationships and sexual functioning. In the present paper we apply a dyadic design to investigate the role of romantic partners' diurnal preferences in determining a variety of relationship outcomes. A sample of 91 heterosexual couples completed a set of questionnaires measuring relationship satisfaction, sexual satisfaction, and morningness-eveningness, and answered questions regarding their actual and preferred time for sexual activity. Conducted analyses revealed that similarity in chronotype between partners and female morningness fostered relationship satisfaction in females, but not in males. Furthermore, morningness-eveningness was associated with preferred time for sex in males, but not in females, who in principle preferred evening hours. Although actual time for sex was up to the female preference, sexual satisfaction in both genders was associated with lower discrepancy in their preferred time for sex and greater frequency of intercourse. In sum, these results indicate that chronotype and time for sex are important factors affecting sexual and relationships satisfaction in heterosexual couples.

Timing of Maternal Depression and Sex-Specific Child Growth, the Upstate KIDS Study.

Science.gov (United States)

Park, Hyojun; Sundaram, Rajeshwari; Gilman, Stephen E; Bell, Griffith; Louis, Germaine M Buck; Yeung, Edwina H

2018-01-01

Equivocal findings have been reported on the association between maternal depression and children's growth, possibly because of the limited attention to its disproportionate impact by child sex. The relationship between the timing of maternal depression and children's growth was assessed in a population-based prospective birth cohort, with particular attention to sex differences. The Upstate KIDS Study comprised 4,394 children followed through 3 years of age from 2008 to 2010. Maternal depression was measured antenatally by linkage with hospital discharge records before delivery and postnatally by depressive symptoms reported from questionnaires. Children's growth was measured by sex- and age-specific weight, height, weight for height, and BMI. Adjusted linear mixed effects models were used to estimate growth outcomes for the full sample and separately by plurality and sex. Antenatal depression was associated with lower weight for age (-0.24 z score units; 95% confidence interval [CI]: -0.43, -0.05) and height for age (-0.26 z score units; 95% CI: -0.51, -0.02) among singleton boys. Postnatal depressive symptoms were associated with higher weight for height (0.21 z score units; 95% CI: 0.01, 0.42) among singleton girls. The findings of this study suggest that antenatal depression was associated with lower weight and smaller height only for boys, whereas postnatal depressive symptoms were associated with higher weight for height only for girls. The timing of depression and the mechanisms of sex-specific responses require further examination. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Optimization of Signal Timing of Intersections by Internal Metering of Queue Time Ratio of Vehicles in Network Scale

Directory of Open Access Journals (Sweden)

Mina Ghanbarikarekani

2016-06-01

Full Text Available Optimization of signal timing in urban network is usually done by minimizing the delay times or queue lengths. Sincethe effect of each intersection on the whole network is not considered in the mentioned methods, traffic congestion may occur in network links. Therefore, this paper has aimed to provide a timing optimization algorithm for traffic signals using internal timing policy based on balancing queue time ratio of vehicles in network links. In the proposed algorithm, the difference between the real queue time ratio and the optimum one for each link of intersection was minimized. To evaluate the efficiency of the proposed algorithm on traffic performance, the proposed algorithm was applied in a hypothetical network. By comparing the simulating software outputs, before and after implementing the algorithm, it was concluded that the queue time ratio algorithm has improved the traffic parameters by increasing the flow as well as reducing the delay time and density of the network.

Sex difference and Allee effects shape the dynamics of sex-structured invasions.

Science.gov (United States)

Shaw, Allison K; Kokko, Hanna; Neubert, Michael G

2018-01-01

The rate at which a population grows and spreads can depend on individual behaviour and interactions with others. In many species with two sexes, males and females differ in key life-history traits (e.g. growth, survival and dispersal), which can scale up to affect population rates of growth and spread. In sexually reproducing species, the mechanics of locating mates and reproducing successfully introduce further complications for predicting the invasion speed (spread rate), as both can change nonlinearly with density. Most models of population spread are based on one sex, or include limited aspects of sex differences. Here we ask whether and how the dynamics of finding mates interact with sex-specific life-history traits to influence the rate of population spread. We present a hybrid approach for modelling invasions of populations with two sexes that links individual-level mating behaviour (in an individual-based model) to population-level dynamics (in an integrodifference equation model). We find that limiting the amount of time during which individuals can search for mates causes a demographic Allee effect which can slow, delay, or even prevent an invasion. Furthermore, any sex-based asymmetries in life history or behaviour (skewed sex ratio, sex-biased dispersal, and sex-specific mating behaviours) amplify these effects. In contrast, allowing individuals to mate more than once ameliorates these effects, enabling polygynandrous populations to invade under conditions where monogamously mating populations would fail to establish. We show that details of individuals' mating behaviour can impact the rate of population spread. Based on our results, we propose a stricter definition of a mate-finding Allee effect, which is not met by the commonly used minimum mating function. Our modelling approach, which links individual- and population-level dynamics in a single model, may be useful for exploring other aspects of individual behaviour that are thought to impact the

Behaviour change and associated factors among female sex workers in Kenya.

Science.gov (United States)

Nyagero, Josephat; Wangila, Samuel; Kutai, Vincent; Olango, Susan

2012-01-01

Initiatives aimed at behaviour change of key populations such as the female sex workers (FSWs) are pivotal in reducing the transmission of HIV. An 8-year implementation research to establish the predictor factors of behaviour change among FSWs in Kenya was initiated by the African Medical Research Foundation (AMREF) with Sida and DfID support. This cross-sectional survey interviewed 159 female sex workers (FSWs) identified through snowball procedure. The measurement of behaviour change was based on: the consistent use of condoms with both regular and non regular clients, reduced number of clients, routine checks for STIs, and involvement in alternative income generating activities. The adjusted odds ratios at 95% confidence interval computed during binary logistic regression analysis were used to determine the behaviour change predictor factors. Most FSWs (84%) had participated in AMREF's integrated intervention programme for at least one year and 59.1% had gone through behaviour change. The adjusted odds ratio showed that the FSWs with secondary education were 2.23 times likely to change behaviour, protestants were 4.61 times, those in sex work for >4 years were 2.36 times, FSWs with good HIV prevention knowledge were 4.37 times, and those engaged in alternative income generating activities were 2.30 times more likely to change their behaviour compared to respective counterparts. Behaviour change among FSWs was possible and is associated with the level of education, religious affiliation, number of years in sex work and one's level of HIV prevention knowledge. A re-orientation on the peer education programme to focus on HIV preventive measures beyond use of condoms is emphasized.

Battle of the Sexes

NARCIS (Netherlands)

Bulte, E.H.; Tu, Q.; List, J.

2015-01-01

A vibrant literature has emerged that explores the economic implications of the sex ratio (the ratio of men to women in the population), including changes in fertility rates, educational outcomes, labor supply, and household purchases. Previous empirical efforts, however, have paid less attention to

Why is digit ratio correlated to sports performance?

Science.gov (United States)

Kim, Tae Beom; Kim, Khae Hawn

2016-12-01

Second to fourth digit ratio is the ratio of second to fourth digit length. It has been known that digit ratio is sexually dimorphic in humans, such that males tend to have lower digit ratio (longer fourth digits relative to second digits) than females. Digit ratio is thought to be a biomarker of the balance between fetal testosterone (FT) and fetal estrogen (FE) in a relatively narrow developmental window at the end of the first trimester of pregnancy. On the contrary, the relationships between digit ratio and levels of sex steroids in adults are not clear. Most correlational studies between digit ratio and adult sex steroids have revealed that this association is statistically not significant. However, for many years, a lot of researches showed negative relationships between digit ratio and sports performance such as rugby, surfing, rowing, sprinting, endurance, and hand grip strength. Here, we discuss possible mechanisms about the relationships between digit ratio and sports performance.

Longevity enhances selection of environmental sex determination.

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Bull, J J; Bulmer, M G

1989-12-01

Environmental sex determination (ESD) is a mechanism in which an individual develops as male or female largely in response to some environmental effect experienced early in life. Its forms range from sex determination by egg incubation temperature in reptiles to sex determination of photoperiod in amphipods. Previous theoretical work as suggested that ESD is favored by natural selection if the fitness consequences of the early environmental experience differ for males and females, so that an individual benefits by being male under some conditions and female under others. A drawback of ESD is that it enables climatic changes to influence the population sex ratio, and such fluctuations select against ESD. This study employed numerical analyses to investigate the balance between these two opposing forces. The negative impact of climatic fluctuations appears to depend greatly on species longevity: substantial between-year fluctuations are of little consequence in selecting against ESD in long-lived species because annual sex ratio fluctuations tend to cancel and thus alter the total population sex ratio only slightly. Thus, if a species is sufficiently long-lived, extreme ESD can be maintained despite only a weak advantage. This result offers one explanation for the failure to demonstrate an advantage for the extreme forms of ESD observed in reptiles.

Selfish element maintains sex in natural populations of a parasitoid wasp.

NARCIS (Netherlands)

Stouthamer, R.; Tilborg, van M.; Jong, de J.H.; Nunney, L.; Luck, R.F.

2001-01-01

Genomic conflicts between heritable elements with different modes of inheritance are important in the maintenance of sex and in the evolution of sex ratio. Generally, we expect sexual populations to exhibit a 1:1 sex ratio. However, because of their biology, parasitoid wasps often exhibit a

Sex Dimorphism of the Heart Diameters and Cardiothoracic Ratios ...

African Journals Online (AJOL)

Objective: To determine gender associated differences in the cardiothoracic ratio (CTR) and heart diameters in a normal Nigerian population. Subject and Method: The normal heart diameters and cardiothoracic ratios were measured from posteroanterior (PA) chest radiographs of healthy 510 male and 508 female ...

The net effect of alternative allocation ratios on recruitment time and trial cost.

Science.gov (United States)

Vozdolska, Ralitza; Sano, Mary; Aisen, Paul; Edland, Steven D

2009-04-01

Increasing the proportion of subjects allocated to the experimental treatment in controlled clinical trials is often advocated as a method of increasing recruitment rates and improving the performance of trials. The presumption is that the higher likelihood of randomization to the experimental treatment will be perceived by potential study enrollees as an added benefit of participation and will increase recruitment rates and speed the completion of trials. However, studies with alternative allocation ratios require a larger sample size to maintain statistical power, which may result in a net increase in time required to complete recruitment and a net increase in total trial cost. To describe the potential net effect of alternative allocation ratios on recruitment time and trial cost. Models of recruitment time and trial cost were developed and used to compare trials with 1:1 allocation to trials with alternative allocation ratios under a range of per subject costs, per day costs, and enrollment rates. In regard to time required to complete recruitment, alternative allocation ratios are net beneficial if the recruitment rate improves by more than about 4% for trials with a 1.5:1 allocation ratio and 12% for trials with a 2:1 allocation ratio. More substantial improvements in recruitment rate, 13 and 47% respectively for scenarios we considered, are required for alternative allocation to be net beneficial in terms of tangible monetary cost. The cost models were developed expressly for trials comparing proportions or means across treatment groups. Using alternative allocation ratio designs to improve recruitment may or may not be time and cost-effective. Using alternative allocation for this purpose should only be considered for trial contexts where there is both clear evidence that the alternative design does improve recruitment rates and the attained time or cost efficiency justifies the added study subject burden implied by a larger sample size.

Changes in Income at Macro Level Predict Sex Ratio at Birth in OECD Countries.

Science.gov (United States)

Kanninen, Ohto; Karhula, Aleksi

2016-01-01

The human sex ratio at birth (SRB) is approximately 107 boys for every 100 girls. SRB was rising until the World War II and has been declining slightly after the 1950s in several industrial countries. Recent studies have shown that SRB varies according to exposure to disasters and socioeconomic conditions. However, it remains unknown whether changes in SRB can be explained by observable macro-level socioeconomic variables across multiple years and countries. Here we show that changes in disposable income at the macro level positively predict SRB in OECD countries. A one standard deviation increase in the change of disposable income is associated with an increase of 1.03 male births per 1000 female births. The relationship is possibly nonlinear and driven by extreme changes. The association varies from country to country being particular strong in Estonia. This is the first evidence to show that economic and social conditions are connected to SRB across countries at the macro level. This calls for further research on the effects of societal conditions on general characteristics at birth.

Assigning sex and reproductive stage to adult Lake Sturgeon using ultrasonography and common morphological measurements

Science.gov (United States)

Chiotti, Justin A.; Boase, James C.; Hondorp, Darryl W.; Briggs, Andrew S.

2016-01-01

Sex determination of fish species is difficult to assess when sexual dimorphism and gametes are not apparent. For threatened and endangered fish species, noninvasive techniques are needed when determining sex to minimize stress and the potential for mortality. We evaluated the use of a portable ultrasound unit to determine sex of Lake Sturgeon Acipenser fulvescens in the field. Ultrasound images were collected from 9 yellow-egg (F2, F3), 32 black-egg (F4, F5), and 107 fully developed male (M2) Lake Sturgeon. Two readers accurately assigned sex to 88–96% of fish, but accuracy varied in relation to maturity stage. Black-egg females and fully developed males were correctly identified for 89–100% of the fish sampled, while these two readers identified yellow-egg females only 33% and 67% of the time. Time spent collecting images ranged between 2 and 3 min once the user was comfortable with operating procedures. Discriminant analysis revealed the total length : girth ratio was a strong predictor of sex and maturity, correctly classifying 81% of black-egg females and 97% of the fully developed males. However, yellow-egg females were incorrectly classified on all occasions. This study shows the utility of using ultrasonography and a total length : girth ratio for sex determination of Lake Sturgeon in later reproductive stages around the spawning season.

Stress and sex: does cortisol mediate sex change in fish?

Science.gov (United States)

Goikoetxea, Alexander; Todd, Erica V; Gemmell, Neil J

2017-12-01

Cortisol is the main glucocorticoid (GC) in fish and the hormone most directly associated with stress. Recent research suggests that this hormone may act as a key factor linking social environmental stimuli and the onset of sex change by initiating a shift in steroidogenesis from estrogens to androgens. For many teleost fish, sex change occurs as a usual part of the life cycle. Changing sex is known to enhance the lifetime reproductive success of these fish and the modifications involved (behavioral, gonadal and morphological) are well studied. However, the exact mechanism behind the transduction of the environmental signals into the molecular cascade that underlies this singular process remains largely unknown. We here synthesize current knowledge regarding the role of cortisol in teleost sex change with a focus on two well-described transformations: temperature-induced masculinization and socially regulated sex change. Three non-mutually exclusive pathways are considered when describing the potential role of cortisol in mediating teleost sex change: cross-talk between GC and androgen pathways, inhibition of aromatase expression and upregulation of amh (the gene encoding anti-Müllerian hormone). We anticipate that understanding the role of cortisol in the initial stages of sex change will further improve our understanding of sex determination and differentiation across vertebrates, and may lead to new tools to control fish sex ratios in aquaculture. © 2017 Society for Reproduction and Fertility.

Association between Pregnancy and Active Injection Drug Use and Sex Work among Women Injection Drug Users in Saint Petersburg, Russia.

Science.gov (United States)

Girchenko, P; Ompad, D C; Bikmukhametov, D; Gensburg, L

2015-06-01

Widespread use of unsafe sexual practices among women injecting drugs both practicing and not practicing sex work leads to high levels of unplanned pregnancies in this population. The goal of this study was to investigate the association between pregnancy and active drug use and sex work. Data were collected using a convenience sample of 500 women in Saint Petersburg, Russia, in 2013. All women had recent experience of drug use, of which 200 were pregnant at the time of the study. The study consisted of a structured interview followed by a rapid HIV test. Pregnancy was protective against both active drug use and sex work. For HIV-positive women, these associations were stronger than for HIV-negative women: drug use prevalence ratio (PR) was 0.59 vs 0.85; for sex work, the PRs were 0.36 vs 0.64. Higher levels of education were associated with a lower prevalence ratio for active drug use and sex work in all models. Having children was not associated with active drug use or sex work. Pregnancy might be an optimal time for conducting interventions aimed at cessation of drug use and sex work among women injecting drugs.

Isolation, identification and field tests of the sex pheromone of the carambola fruit borer, Eucosma notanthes.

Science.gov (United States)

Hung, C C; Hwang, J S; Hung, M D; Yen, Y P; Hou, R F

2001-09-01

Two components, (Z)-8-dodecenyl acetate (Z8-12:Ac) and (Z)-8-dodecenol (Z8-12:OH), were isolated from sex pheromone glands of the carambola fruit borer, Eucosma notanthes, and were identified by GC, and GC-MS, chemical derivatization, and comparison of retention times. The ratio of the alcohol to acetate in the sex pheromone extracts was 2.7. However, synthetic mixtures (1 mg) in ratios ranging from 0.5 to 1.5 were more effective than other blends in trapping male moths in field tests.

Influence of gender preference and sex composition of surviving ...

African Journals Online (AJOL)

Women who have GP and same LCSC were 1.35 and 2.4 times significantly more likely to have intention to bear more children than those who have no GP and different sexes composition respectively. These odd ratios changed to 1.38 for GP and 2.44 for LCSC after adjusting for other socio-demographic variables.

Genes and chromosome arrangements affecting sex ratio in the Mediterranean fruit fly, Ceratitis capitata (Wied.)

International Nuclear Information System (INIS)

Wood, R.J.; Kafu, A.A.; Rendon Arana, P.A.; Owusu-Daaku, K.; Alcock, R.M.; Hallows, J.A.; Busch-Petersen, E.; Mani, G.S.

1997-01-01

The MP (male producing) factor, which shows temperature sensitive meiotic drive favoring the Y chromosome, proved to be highly variable in spermatozoal deficiency in different cysts within a single testis. However, the overall loss of sperm corresponded almost precisely with the loss of females. The minimum proportion of females consistently obtained in inbred lines was about 30-35%. On the basis of parallel studies with the mosquito Aedes aegypti, variability between cysts is open to interpretation in terms of different rates of senescence. The T:Y(wp + )30C genetic sexing strain, which is designed to generate males with brown (wild type) puparia and females with white puparia, was contaminated artificially in a series of population experiments to investigate the pattern of breakdown. Wild type contamination with either sex caused an increase of brown pupae. The sex ratio became progressively distorted in favour of females after contamination with females, mated or unmated, but not after male contamination. The experiments revealed evidence of a low frequency of natural recombination between wp + and the translocation breakpoint on the Y chromosome, shown by the appearance of wp males. The frequency of male recombination (r) and the selection coefficient (s) against wp/wp were measured over 11 generations. The best fit to the observed data was obtained with r = (0.14 ± 0.04)% and s=(26.0 ± 2.7)%. Using these estimates to predict the frequency of wp + females and wp males for up to 100 generations, it was concluded that white males would never exceed 0.5% whereas the frequency of brown females was expected to exceed 33% after 25 generations. Published data on the mass reared strain, maintained with a population size of 240,000 adult flies, were subjected to the same analysis. A higher value of s between (38.0 ± 3.2)% and (52.0 ± 0.3)% was obtained under these conditions. Electrophoretic studies on esterases revealed a significantly higher activity in a recently

Study of change of sex hormone receptors in diabetic impotent patients

International Nuclear Information System (INIS)

Zhang Yong; Chen Weizhen; Zhang Zikang; Hu Xiaoke

2002-01-01

To study the relationship between diabetic impotence and sex hormones as well as sex hormone receptors. 32 diabetic impotent patients, 32 diabetic patients with normal sex function, 32 impotent patients without diabetes, and 40 healthy men were enrolled. The plasma sex hormone levels were examined by radioimmunoassay, and sex hormone receptors in white blood cells by radioreceptor assay. Compared with healthy men and impotent patients without diabetes, PRL levels in both diabetic impotent patients and diabetic patients with normal sex function increased markedly, T and AR levels decreased, and the ratio of E 2 /T and ER/AR increased. Compared with diabetic patients with normal sex function, while there was no significant difference in PRL, T and E 2 /T ratio, the AR level of diabetic impotent patients further decreased, and the ER/AR ratio further increased. Negative correlation was found between age and AR as well as T. The decline of AR and the increase of ER/AR ratio might be one main cause of diabetic impotence. And the decline of T and AR might be an important cause of the increase of diabetic impotence incidence with age

The RATIO method for time-resolved Laue crystallography

International Nuclear Information System (INIS)

Coppens, P.; Pitak, M.; Gembicky, M.; Messerschmidt, M.; Scheins, S.; Benedict, J.; Adachi, S.-I.; Sato, T.; Nozawa, S.; Ichiyanagi, K.; Chollet, M.; Koshihara, S.-Y.

2009-01-01

A RATIO method for analysis of intensity changes in time-resolved pump-probe Laue diffraction experiments is described. The method eliminates the need for scaling the data with a wavelength curve representing the spectral distribution of the source and removes the effect of possible anisotropic absorption. It does not require relative scaling of series of frames and removes errors due to all but very short term fluctuations in the synchrotron beam.

Restoration ecology: two-sex dynamics and cost minimization.

Directory of Open Access Journals (Sweden)

Ferenc Molnár

Full Text Available We model a spatially detailed, two-sex population dynamics, to study the cost of ecological restoration. We assume that cost is proportional to the number of individuals introduced into a large habitat. We treat dispersal as homogeneous diffusion in a one-dimensional reaction-diffusion system. The local population dynamics depends on sex ratio at birth, and allows mortality rates to differ between sexes. Furthermore, local density dependence induces a strong Allee effect, implying that the initial population must be sufficiently large to avert rapid extinction. We address three different initial spatial distributions for the introduced individuals; for each we minimize the associated cost, constrained by the requirement that the species must be restored throughout the habitat. First, we consider spatially inhomogeneous, unstable stationary solutions of the model's equations as plausible candidates for small restoration cost. Second, we use numerical simulations to find the smallest rectangular cluster, enclosing a spatially homogeneous population density, that minimizes the cost of assured restoration. Finally, by employing simulated annealing, we minimize restoration cost among all possible initial spatial distributions of females and males. For biased sex ratios, or for a significant between-sex difference in mortality, we find that sex-specific spatial distributions minimize the cost. But as long as the sex ratio maximizes the local equilibrium density for given mortality rates, a common homogeneous distribution for both sexes that spans a critical distance yields a similarly low cost.

Restoration ecology: two-sex dynamics and cost minimization.

Science.gov (United States)

Molnár, Ferenc; Caragine, Christina; Caraco, Thomas; Korniss, Gyorgy

2013-01-01

We model a spatially detailed, two-sex population dynamics, to study the cost of ecological restoration. We assume that cost is proportional to the number of individuals introduced into a large habitat. We treat dispersal as homogeneous diffusion in a one-dimensional reaction-diffusion system. The local population dynamics depends on sex ratio at birth, and allows mortality rates to differ between sexes. Furthermore, local density dependence induces a strong Allee effect, implying that the initial population must be sufficiently large to avert rapid extinction. We address three different initial spatial distributions for the introduced individuals; for each we minimize the associated cost, constrained by the requirement that the species must be restored throughout the habitat. First, we consider spatially inhomogeneous, unstable stationary solutions of the model's equations as plausible candidates for small restoration cost. Second, we use numerical simulations to find the smallest rectangular cluster, enclosing a spatially homogeneous population density, that minimizes the cost of assured restoration. Finally, by employing simulated annealing, we minimize restoration cost among all possible initial spatial distributions of females and males. For biased sex ratios, or for a significant between-sex difference in mortality, we find that sex-specific spatial distributions minimize the cost. But as long as the sex ratio maximizes the local equilibrium density for given mortality rates, a common homogeneous distribution for both sexes that spans a critical distance yields a similarly low cost.

Sex Differences in Mortality Based on United Network for Organ Sharing Status While Awaiting Heart Transplantation.

Science.gov (United States)

Hsich, Eileen M; Blackstone, Eugene H; Thuita, Lucy; McNamara, Dennis M; Rogers, Joseph G; Ishwaran, Hemant; Schold, Jesse D

2017-06-01

There are sex differences in mortality while awaiting heart transplantation, and the reason remains unclear. We included all adults in the Scientific Registry of Transplant Recipients placed on the heart transplant active waitlist from 2004 to 2015. The primary end point was all-cause mortality. Multivariable Cox proportional hazards models were performed to evaluate survival by United Network for Organ Sharing (UNOS) status at the time of listing. Random survival forest was used to identify sex interactions for the competing risk of death and transplantation. There were 33 069 patients (25% women) awaiting heart transplantation. This cohort included 7681 UNOS status 1A (26% women), 13 027 UNOS status 1B (25% women), and 12 361 UNOS status 2 (26% women). During a median follow-up of 4.3 months, 1351 women and 4052 men died. After adjusting for >20 risk factors, female sex was associated with a significant risk of death among UNOS status 1A (adjusted hazard ratio, 1.14; 95% confidence interval, 1.01-1.29) and UNOS status 1B (adjusted hazard ratio, 1.17; 95% confidence interval, 1.05-1.30). In contrast, female sex was significantly protective for time to death among UNOS status 2 (adjusted hazard ratio, 0.85; 95% confidence interval, 0.76-0.95). Sex differences in probability of transplantation were present for every UNOS status, and >20 sex interactions were identified for mortality and transplantation. When stratified by initial UNOS status, women had a higher mortality than men as UNOS status 1 and a lower mortality as UNOS status 2. With >20 sex interactions for mortality and transplantation, further evaluation is warranted to form a more equitable allocation system. © 2017 American Heart Association, Inc.

Rates of advertised condomless sex in the online profiles of private sex workers: a cross-sectional study.

Science.gov (United States)

Blackledge, Edjoni; Thng, Caroline; McIver, Ruthy; McNulty, Anna

2018-02-01

This study aimed to assess the level of condomless sex advertised online by private sex workers (PSW) in Sydney. In 2015, 750 online profiles of PSW, including 339 female, 53 male and 39 transgender PSWs, were reviewed. It was found that PSWs advertise protected anal and vaginal sex. However, 50% of female PSW advertised condomless oral sex. Age less than 25 years was associated with advertised condomless oral sex (odds ratio 1.56; 95% confidence interval 1.03-2.37; P=0.037). Online platforms are widely used for advertising, especially by female PSWs. Levels of condom use advertised reflect that of other studies of sex workers in Sydney.

DNA Methylation and Sex Allocation in the Parasitoid Wasp Nasonia vitripennis.

Science.gov (United States)

Cook, Nicola; Pannebakker, Bart A; Tauber, Eran; Shuker, David M

2015-10-01

The role of epigenetics in the control and evolution of behavior is being increasingly recognized. Here we test whether DNA methylation influences patterns of adaptive sex allocation in the parasitoid wasp Nasonia vitripennis. Female N. vitripennis allocate offspring sex broadly in line with local mate competition (LMC) theory. However, recent theory has highlighted how genomic conflict may influence sex allocation under LMC, conflict that requires parent-of-origin information to be retained by alleles through some form of epigenetic signal. We manipulated whole-genome DNA methylation in N. vitripennis females using the hypomethylating agent 5-aza-2'-deoxycytidine. Across two replicated experiments, we show that disruption of DNA methylation does not ablate the facultative sex allocation response of females, as sex ratios still vary with cofoundress number as in the classical theory. However, sex ratios are generally shifted upward when DNA methylation is disrupted. Our data are consistent with predictions from genomic conflict over sex allocation theory and suggest that sex ratios may be closer to the optimum for maternally inherited alleles.

Nuclear fuel, mass balances, conversion ratio, doubling time, and uncertainty

International Nuclear Information System (INIS)

Vondy, D.R.

1976-11-01

Information on the performance aspects of nuclear power plants is presented concerning conversion ratio, criticality, primitive economic analysis, stable breeder-converter industry, doubling time, breeder industry economic benefit, defining nuclear fuel, recommendations, and uncertainty

Neutrophil-lymphocyte ratio and platelet-lymphocyte ratio as predictors of wound healing failure in head and neck reconstruction.

Science.gov (United States)

Maruyama, Yoko; Inoue, Keita; Mori, Keita; Gorai, Katsuya; Shimamoto, Ryo; Onitsuka, Tetsuro; Iguchi, Hiroyoshi; Okazaki, Mutsumi; Nakagawa, Masahiro

2017-01-01

In microsurgical head and neck reconstruction, a higher rate of post-operative wound complication could be predicted by a lower pre-operative neutrophil ratio (wound complications in microsurgical head and neck reconstruction. Patients who were undergoing tumor ablation and microsurgical reconstruction from April 2011 to March 2014 were analyzed retrospectively. The pre-operative hematological data, age, sex, co-morbidities, body mass index (BMI), adjuvant therapies, smoking, operation time, blood loss, total protein, T-stage, and Anesthesiologists Performance Status (ASA-PS) score were collected. Cases of post-operative wound healing failure were reviewed. One hundred and three consecutive patients were enrolled. Among these, the results of 77 patients who were younger than 70 years of age were analyzed. The distributions of the neutrophil ratio (p = .0005), lymphocyte ratio (p = .0166), monocyte ratio (p = .0341), NLR (p = .005), and PLR (p = .008) differed significantly between the patients with and without post-operative wound healing failure. Neutrophil ratio, NLR, and PLR cut-off values of 64.9, 3.5, and 160 were significantly associated with the rate of wound healing failure rate (p = .0002, .00021, .0042, respectively).

The Impact of Handedness, Sex, and Cognitive Abilities on Left–Right Discrimination: A Behavioral Study

Science.gov (United States)

Constant, Martin; Mellet, Emmanuel

2018-01-01

The present study examined the relationship between left–right discrimination (LRD) performance and handedness, sex and cognitive abilities. In total, 31 men and 35 women – with a balanced ratio of left-and right-handers – completed the Bergen Left–Right Discrimination Test. We found an advantage of left-handers in both identifying left hands and in verifying “left” propositions. A sex effect was also found, as women had an overall higher error rate than men, and increasing difficulty impacted their reaction time more than it did for men. Moreover, sex interacted with handedness and manual preference strength. A negative correlation of LRD reaction time with visuo-spatial and verbal long-term memory was found independently of sex, providing new insights into the relationship between cognitive skills and performance on LRD. PMID:29636718

Divorce, Abortion and Children's Sex Ratio: The Impact of Divorce Reform in China

OpenAIRE

Sun, Ang; Zhao, Yaohui

2014-01-01

This paper explores how the relative circumstances of men and women following marital dissolution affect sex-selection behavior within marriages. China's 2001 divorce reform liberalized divorce in favor of women and secured women's property rights after separation. We use this improvement in women's bargaining power in marriage for a regression discontinuity analysis of the demand for sex-selective abortions. We show that the increase in women's bargaining power reduces the propensity to have...

Segregating variation for temperature-dependent sex determination in a lizard.

Science.gov (United States)

Rhen, T; Schroeder, A; Sakata, J T; Huang, V; Crews, D

2011-04-01

Temperature-dependent sex determination (TSD) was first reported in 1966 in an African lizard. It has since been shown that TSD occurs in some fish, several lizards, tuataras, numerous turtles and all crocodilians. Extreme temperatures can also cause sex reversal in several amphibians and lizards with genotypic sex determination. Research in TSD species indicates that estrogen signaling is important for ovary development and that orthologs of mammalian genes have a function in gonad differentiation. Nevertheless, the mechanism that actually transduces temperature into a biological signal for ovary versus testis development is not known in any species. Classical genetics could be used to identify the loci underlying TSD, but only if there is segregating variation for TSD. Here, we use the 'animal model' to analyze inheritance of sexual phenotype in a 13-generation pedigree of captive leopard geckos, Eublepharis macularius, a TSD reptile. We directly show genetic variance and genotype-by-temperature interactions for sex determination. Additive genetic variation was significant at a temperature that produces a female-biased sex ratio (30°C), but not at a temperature that produces a male-biased sex ratio (32.5°C). Conversely, dominance variance was significant at the male-biased temperature (32.5°C), but not at the female-biased temperature (30°C). Non-genetic maternal effects on sex determination were negligible in comparison with additive genetic variance, dominance variance and the primary effect of temperature. These data show for the first time that there is segregating variation for TSD in a reptile and consequently that a quantitative trait locus analysis would be practicable for identifying the genes underlying TSD.

Poor School Bonding and Delinquency over Time: Bidirectional Effects and Sex Differences

Science.gov (United States)

Liljeberg, Jenny Freidenfelt; Eklund, Jenny M.; Fritz, Marie Vafors; Klinteberg, Britt af

2011-01-01

The association between poor school bonding and delinquency has only been partly addressed in earlier research. Using a longitudinal design, the objective of our study was to investigate possible bidirectional effects and sex differences between adolescents' experienced school bonding and self-rated delinquency over time. A total of 788…

Sex determination in Madagascar geckos of the genus Paroedura (Squamata: Gekkonidae): are differentiated sex chromosomes indeed so evolutionary stable?

Science.gov (United States)

Koubová, Martina; Johnson Pokorná, Martina; Rovatsos, Michail; Farkačová, Klára; Altmanová, Marie; Kratochvíl, Lukáš

2014-12-01

Among amniote vertebrates, geckos represent a clade with exceptional variability in sex determination; however, only a minority of species of this highly diverse group has been studied in this respect. Here, we describe for the first time a female heterogamety in the genus Paroedura, the group radiated in Madagascar and adjacent islands. We identified homomorphic ZZ/ZW sex chromosomes with a highly heterochromatic W chromosome in Paroedura masobe, Paroedura oviceps, Paroedura karstophila, Paroedura stumpffi, and Paroedura lohatsara. Comparative genomic hybridization (CGH) revealed that female-specific sequences are greatly amplified in the W chromosome of P. lohatsara and that P. gracilis seems to possess a derived system of multiple sex chromosomes. Contrastingly, neither CGH nor heterochromatin visualization revealed differentiated sex chromosomes in the members of the Paroedura picta-Paroedura bastardi-Paroedura ibityensis clade, which is phylogenetically nested within lineages with a heterochromatic W chromosome. As a sex ratio consistent with genotypic sex determination has been reported in P. picta, it appears that the members of the P. picta-P. bastardi-P. ibityensis clade possess homomorphic, poorly differentiated sex chromosomes and may represent a rare example of evolutionary loss of highly differentiated sex chromosomes. Fluorescent in situ hybridization (FISH) with a telomeric probe revealed a telomere-typical pattern in all species and an accumulation of telomeric sequences in the centromeric region of autosomes in P. stumpffi and P. bastardi. Our study adds important information for the greater understanding of the variability and evolution of sex determination in geckos and demonstrates how the geckos of the genus Paroedura provide an interesting model for studying the evolution of the sex chromosomes.

Does the dose-solubility ratio affect the mean dissolution time of drugs?

Science.gov (United States)

Lánský, P; Weiss, M

1999-09-01

To present a new model for describing drug dissolution. On the basis of the new model to characterize the dissolution profile by the distribution function of the random dissolution time of a drug molecule, which generalizes the classical first order model. Instead of assuming a constant fractional dissolution rate, as in the classical model, it is considered that the fractional dissolution rate is a decreasing function of the dissolved amount controlled by the dose-solubility ratio. The differential equation derived from this assumption is solved and the distribution measures (half-dissolution time, mean dissolution time, relative dispersion of the dissolution time, dissolution time density, and fractional dissolution rate) are calculated. Finally, instead of monotonically decreasing the fractional dissolution rate, a generalization resulting in zero dissolution rate at time origin is introduced. The behavior of the model is divided into two regions defined by q, the ratio of the dose to the solubility level: q 1 (saturation of the solution, saturation time). The singular case q = 1 is also treated and in this situation the mean as well as the relative dispersion of the dissolution time increase to infinity. The model was successfully fitted to data (1). This empirical model is descriptive without detailed physical reasoning behind its derivation. According to the model, the mean dissolution time is affected by the dose-solubility ratio. Although this prediction appears to be in accordance with preliminary application, further validation based on more suitable experimental data is required.

EFFECTS OF STRESSFUL EVENTS IN FRANCE (1968) AND JAPAN (1995) ON THE SEX RATIO AT BIRTH.

Science.gov (United States)

Grech, Victor; Zammit, Dorota; Scherb, Hagen

2017-09-01

Males are usually born in excess of females. The sex ratio at birth (SR) is often expressed as the ratio of male to total births. A wide variety of factors have been shown to influence SR, including terrorist attacks, which have been shown to reduce SR. This paper reviews the effects on SR outcomes of the stressful events in France in 1968 (in association with the student and worker riots) and in Japan following the Aum Shinrikyo religious cult's attack on the Tokyo subway using sarin nerve gas in 1995. Both countries displayed seasonal variation in SR. France exhibited a decline in SR in 1968 (p=0.042), with a particularly strong dip in May of that year (p=0.015). For Japan, there was no statistically significant dip for 1995 but there was a significant dip in June of that year (p=0.026). The SR dips follow catastrophic or tragic events if these are perceived to be momentous enough by a given populace. It is believed that SR slumps may be caused by population stress, which is known to lead to the culling of frail/small male fetuses. It has been observed that these fluctuations are comparable in intensity to a substantial proportion of quoted values for perinatal mortality, potentially making this a public health issue.

Sex differences in accuracy and precision when judging time to arrival: data from two Internet studies.

Science.gov (United States)

Sanders, Geoff; Sinclair, Kamila

2011-12-01

We report two Internet studies that investigated sex differences in the accuracy and precision of judging time to arrival. We used accuracy to mean the ability to match the actual time to arrival and precision to mean the consistency with which each participant made their judgments. Our task was presented as a computer game in which a toy UFO moved obliquely towards the participant through a virtual three-dimensional space on route to a docking station. The UFO disappeared before docking and participants pressed their space bar at the precise moment they thought the UFO would have docked. Study 1 showed it was possible to conduct quantitative studies of spatiotemporal judgments in virtual reality via the Internet and confirmed reports that men are more accurate because women underestimate, but found no difference in precision measured as intra-participant variation. Study 2 repeated Study 1 with five additional presentations of one condition to provide a better measure of precision. Again, men were more accurate than women but there were no sex differences in precision. However, within the coincidence-anticipation timing (CAT) literature, of those studies that report sex differences, a majority found that males are both more accurate and more precise than females. Noting that many CAT studies report no sex differences, we discuss appropriate interpretations of such null findings. While acknowledging that CAT performance may be influenced by experience we suggest that the sex difference may have originated among our ancestors with the evolutionary selection of men for hunting and women for gathering.

Sex allocation in the sexually monomorphic fairy martin

NARCIS (Netherlands)

Magrath, MJL; Green, DJ; Komdeur, J

Offspring sex ratios were examined at the population and family level in the sexually monomorphic, socially monogamous fairy martin Petrochelidon ariel at five colony sites over a 4-year period (1993 1996). The sex of 465 nestlings from 169 broods % as determined using sex-specific PCR at the CHD

In the Pursuit of Sons: Additional Births or Sex-Selective Abortion in Pakistan?

Science.gov (United States)

Zaidi, Batool; Morgan, S Philip

2016-12-01

Even though Pakistan is a highly patriarchal society, it has not featured prominently in studies focusing on sex-selective abortion and sex ratios at birth. But with fertility declining and existing strong son preference-Pakistan has one of the highest desired sex ratios in the world-how will Pakistani families respond? In the pursuit of sons, will they have additional children or resort to sex-selective abortions? Or is there evidence that the pursuit of sons is weakening? Using data from three rounds of the demographic and health survey, we show clear evidence of son preference in fertility intentions, patterns of contraceptive use and parity progression ratios. More specifically, we find pervasive evidence that Pakistanis continue childbearing to have a son, to have more than one son and to have at least one daughter. We do not find consistent and convincing evidence that sex ratios at birth (which indicate sex-selective abortion) are increasing.

Effect of Coating Solvent Ratio on the Drug Release Lag Time of ...

African Journals Online (AJOL)

Purpose: The aim of the study was to investigate the effect of hydro-alcohol coating solvent ratio on the surface texture and lag time of porous theophylline osmotic tablet. Methods: Porous theophylline osmotic pump tablets were formulated by direct compression and coated by spraying with varying ratios of water-alcohol ...

Does the mechanism of sex determination constrain the potential for sex manipulation? A test in geckos with contrasting sex-determining systems

Science.gov (United States)

Kratochvíl, Lukáš; Kubička, Lukáš; Landová, Eva

2008-03-01

The concentration of yolk steroids was suggested to influence offspring gender in oviparous animals subject to both temperature-dependent sex determination (TSD) and genotypic sex determination (GSD). However, the proposed mechanisms of steroid effects are thought to differ between TSD and GSD: a direct effect of oestrogens on gonad feminisation in TSD species vs a differential induction of male-producing or female-producing gametes in GSD species. Geckos offer an ideal opportunity for testing these suggested mechanisms. Closely related gecko species differ in their modes of sex determination. They lay clutches of two synchronously formed eggs; both eggs share equal steroid levels. If identical hormonal composition and environment during vitellogenesis, gravidity and incubation determine the sex of the progeny, siblings should share the same gender in both TSD and GSD geckos. We found strong support for this prediction in a TSD gecko species. Among clutches that were incubated at the temperature that produced both sexes, there were no clutches with siblings of the opposite sex. On the other hand, about half of the clutches yielded siblings of the opposite sex in four GSD species. These results suggest that sex-determining systems constrain the ability of the female to produce single-sex siblings and, hence, it seems that the GSD mechanism constrains the opportunities for sex ratio manipulation in geckos via yolk steroid manipulation.

Systems Biology and Ratio-Based, Real-Time Disease Surveillance.

Science.gov (United States)

Fair, J M; Rivas, A L

2015-08-01

Most infectious disease surveillance methods are not well fit for early detection. To address such limitation, here we evaluated a ratio- and Systems Biology-based method that does not require prior knowledge on the identity of an infective agent. Using a reference group of birds experimentally infected with West Nile virus (WNV) and a problem group of unknown health status (except that they were WNV-negative and displayed inflammation), both groups were followed over 22 days and tested with a system that analyses blood leucocyte ratios. To test the ability of the method to discriminate small data sets, both the reference group (n = 5) and the problem group (n = 4) were small. The questions of interest were as follows: (i) whether individuals presenting inflammation (disease-positive or D+) can be distinguished from non-inflamed (disease-negative or D-) birds, (ii) whether two or more D+ stages can be detected and (iii) whether sample size influences detection. Within the problem group, the ratio-based method distinguished the following: (i) three (one D- and two D+) data classes; (ii) two (early and late) inflammatory stages; (iii) fast versus regular or slow responders; and (iv) individuals that recovered from those that remained inflamed. Because ratios differed in larger magnitudes (up to 48 times larger) than percentages, it is suggested that data patterns are likely to be recognized when disease surveillance methods are designed to measure inflammation and utilize ratios. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Sex workers talk about sex work: six contradictory characteristics of legalised sex work in Melbourne, Australia.

Science.gov (United States)

Begum, Sufia; Hocking, Jane S; Groves, Jan; Fairley, Christopher K; Keogh, Louise A

2013-01-01

Despite research suggesting that legal sex work is safe and that emotional risks and social stigma are of greater concern than health risks, much research on sex work has focused on health risks. Given the legalisation of sex work in Victoria, Australia, it is timely to look beyond health. Three focus groups were conducted with a total of 14 female sex workers on their experience of legal sex work, both positive and negative, and the social acceptability of their profession. Thematic analysis was used to identify the key ways that sex workers described sex work. Women saw legal sex work as safer than illegal sex work, but still not socially acceptable. However, they also described six contradictory elements of sex work, which was seen as: financially rewarding and entrapping; empowering and demeaning; increasing some opportunities while reducing others; flexible and demanding; offering both intimacy and competition; and leading to a 'double life'. While legalisation has improved the safety of sex work, stigma and discrimination persist.

Do sex-specific densities affect local survival of free-ranging great tits?

NARCIS (Netherlands)

Michler, Stephanie P. M.; Nicolaus, Marion; Ubels, Richard; van der Velde, Marco; Both, Christiaan; Tinbergen, Joost M.; Komdeur, Jan

2011-01-01

Competition within sexes is expected when resources are sex specific, whereas competition between sexes can occur when similar resources are exploited. Local population density and sex ratio will determine the amount of sex-specific interactions and thus the potential degree of sex-specific

Impact of timing of sex education on teenage pregnancy in Nigeria: cross-sectional survey of secondary school students.

Science.gov (United States)

Ochiogu, Ifeoma N; Miettola, Juhani; Ilika, Amobi L; Vaskilampi, Tuula

2011-06-01

The objective of this study was to explore whether the time at which sex education was provided had any impact on reported cases of unintended pregnancies. A cross-sectional survey of secondary school students and their teachers was conducted using self-administered questionnaires. The participants were 1,234 students aged 14-17 years and 46 teachers in 5 secondary schools in South Eastern Nigeria. The outcome measures were reported pregnancies within the last 3 years by type of school and class level; class level at the time of receiving sex education at school; and age at the time of receiving sex education at home. In all schools, sex education was provided at all the junior and senior secondary school levels (JSS and SSS, respectively). Overall, reported cases of unintended pregnancies were highest among the junior students. In the private schools, four in ten teachers reported pregnancies among JSS 3 students. Almost four in ten teachers in public schools reported pregnancies among JSS 2 students. Of all the students, about three in ten reported pregnancies among JSS 2 and 3 students respectively. At home, sex education was provided at the mean age of 16 years (SD ± 2.2). All participants cited financial need and marital promise as major predisposing factors. About four in ten students did not use contraceptives during their first sexual experience. This study highlights the need to introduce sex education much earlier, possibly before the JSS levels. At home, sex education may have greater impact if provided before the age of 14 years. Efforts should be made to address the factors predisposing to teenage pregnancy.