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Sample records for carapo gymnotidae gymnotiformes

  1. Electrolocation-communication discharges of the fish Gymnotus carapo L. (Gymnotidae: Gymnotiformes during behavioral sleep

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    Stopa R.M.

    1999-01-01

    Full Text Available Technical problems have hampered the study of sleep in teleosts. The electrical discharges of Gymnotus carapo L. (Gymnotidae: Gymnotiformes were monitored to evaluate their ease and reliability as parameters to study sleep. The discharges were detected by electrodes immersed in a glass aquarium and were recorded on a conventional polygraph. G. carapo showed conspicuous signs of behavioral sleep. During these periods, opercular beat rates were counted, electric discharges recorded, and the "sharp discharge increase" (SDI of the orienting reflex was investigated. All 20 animals monitored maintained electrical discharges during behavioral sleep. The discharge frequencies during sleep (50.3 ± 10.4 Hz were not significantly different from those observed when the fish was awake and inactive (57.2 ± 12.1 Hz (Wilcoxon matched-pairs signed-ranks test, P>0.05. However, the SDI, which was prevalent in the awake fish, was not observed during periods of behavioral sleep. Additional observations showed that the species had cannibalistic habits. When presented with electrical discharges from a conspecific, the sleeping fish showed an initial decrease or pause in discharge frequency, while the awake fish did not have this response. We conclude that the electrical discharges of G. carapo were not conspicuous indicators of behavioral sleep. Discharges may have been maintained during sleep for sensory purposes, i.e., conspecific detection and avoidance of cannibalistic attacks.

  2. Two new species of Nomimoscolex (Cestoda: Proteocephalidea, Monticelliidae from Gymnotus carapo (Pisces: Gymnotiformes in Argentina

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    Pertierra Alicia A Gil de

    2003-01-01

    Full Text Available Nomimoscolex guillermoi n. sp. and N. dechambrieri n. sp. are described from the gymnotiform fish Gymnotus carapo from Argentina. The new species are placed into Nomimoscolex based on the cortical position of the vitelline follicles, and medullary position of the testes, ovary, and uterus. Both species were compared to the 13 species considered valid in the genus. The combination of features distinguishing N. guillermoi from N. dechambrieri is (1 the position of the vagina to cirrus pouch (anterior or posterior vs always anterior respectively, (2 the total number of testes (41-85 vs 108-130 respectively, (3 the distribution of the vitelline follicles (arranged in dorso-lateral and ventro-lateral bands vs lateral bands respectively, (4 the length of the uteroduct (ending 58% vs 35% from posterior margin of mature proglottis respectively, and (5 the presence of gland cells in the scolex (unicellular glands in the apical region and the external margin of suckers vs the presence of unicellular glands in the apex and other grouped in a cluster medially to the suckers respectively.

  3. Reproductive biology of a population of Gymnotus aff.carapo (Teleostei: Gymnotidae from southern Brazil

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    Diego de Paula Cognato

    Full Text Available The reproductive period and its relation with somatic and abiotic factors, the relative and absolute fecundity, spawning type, length of first maturation and sex ratio is describe for Gymnotus aff.carapo from a small lake at Itapuã State Park, Rio Grande do Sul, Brazil. Gymnotus aff. carapo presents a relatively long reproductive cycle extending from November/2003 to March/2004. Decreases in water conductivity and increases in dissolved oxygen are correlated with increased gonadal development in males. In females, seasonal increases in temperature and photoperiod and decreases in dissolved oxygen are correlated with increased gonadal development. The mean absolute fecundity was 915.3 oocytes, and mean relative fecundity 0.20 oocytes/mg body weight. Egg size distributions indicate multiple spawning. The size of first maturation was 141 mm in females and 146 mm in males. The sex ratio was 1:1, with a male bias only in smaller size classes.

  4. Revision of Gymnotus (Gymnotiformes: Gymnotidae) from the Upper Madeira Basin of Bolivia and Peru, with descriptions of two new species.

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    Craig, Jack M; Correa-roldÁn, Vanessa; Ortega, HernÁn; Crampton, William G R; Albert, James S

    2018-04-20

    Banded Knifefishes (Gymnotus, Gymnotidae) comprise the most species-rich genus of Neotropical electric fishes, with 41 species currently described from throughout the humid Neotropics, from Mexico to Argentina. Despite substantial alpha-taxonomic work in recent years, the diversity of Gymnotus in some regions remains poorly understood. Here we describe the Gymnotus fauna of the Upper Madeira basin of Bolivia and Peru from examination of more than 240 adult specimens. Species are delimited and described using body proportions (traditional morphometrics), fin-ray, squamation and laterosensory-pore counts (meristics), quantitative shape differences (geometric morphometrics), osteological traits, and color patterns. Comparisons of standardized linear measures as well as multivariate statistical methods validate the presence in the Upper Madeira basin of three previously described species, two with wide-spread geographic distributions throughout Greater Amazonia (G. carapo and G. coropinae), and one (G. chaviro) endemic to southwestern Amazonia. We also diagnose and describe two new species that are endemic to the Upper Madeira basin: G. eyra n. sp., morphologically most similar to G. mamiraua from lowland Amazonia, and G. riberalta n. sp., morphologically most similar to G. pantanal from the Paraguay-Paraná basin. The five Gymnotus species from the Upper Madeira basin are not monophyletic, each species being more closely related to a different species from another region; i.e. the Gymnotus species from the Upper Madeira represents a polyphyletic assemblage. These descriptions to 43 the number of valid Gymnotus species.

  5. Karyotypic diversity in four species of the genus Gymnotus Linnaeus, 1758 (Teleostei, Gymnotiformes, Gymnotidae): physical mapping of ribosomal genes and telomeric sequences

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    Scacchetti, Priscilla Cardim; Pansonato-Alves, José Carlos; Utsunomia, Ricardo; Oliveira, Claudio; Foresti, Fausto

    2011-01-01

    Abstract Conventional (Giemsa, C-Banding, Ag-NORs, CMA3) and molecular (5S rDNA, 18S rDNA, telomeric sequences) cytogenetic studies were carried out in specimens of ten distinct fish populations of the genus Gymnotus (Gymnotus sylvius Albert and Fernandes-Matioli, 1999, Gymnotus inaequilabiatus Valenciennes, 1839, Gymnotus pantherinus Steindachner, 1908, and G. cf. carapo Linnaeus, 1758) from different Brazilian hydrographic basins. Gymnotus sylvius presented a diploid number of 40 chromosomes (22m+12sm+6st), Gymnotus pantherinus presented 52 chromosomes (32m+18sm+2st), while Gymnotus inaequilabiatus (42m+10sm+2a)and Gymnotus cf. carapo (38m+12sm+4st) presented 54 chromosomes. The C-banding technique revealed centromeric marks in all chromosomes of all species. Besides that, conspicuous blocks of heterochromatin were found interstitially on the chromosomes of Gymnotus inaequilabiatus, Gymnotus cf. carapo,and Gymnotus pantherinus. All four species showed single nucleolus organizing regions confirmed by results obtained through Ag-NORs and FISH experiments using 18S rDNA probes, which showed the NORs localized on the first chromosome pair in Gymnotus inaequilabiatus, Gymnotus cf. carapo,and Gymnotus pantherinus, and on pair 2 in Gymnotus sylvius. CMA3 staining revealed additional unrelated NORs marks in Gymnotus sylvius and Gymnotus pantherinus. The 5S rDNA probes revealed signals on one pair in Gymnotus sylvius and two pairs in Gymnotus pantherinus; Gymnotus inaequilabiatus had about seventeen pairs marked, and Gymnotus cf. carapo had about fifteen pairs marked. It is considered that the high amount of heterochromatin identified in the chromosomes of Gymnotus inaequilabiatus and Gymnotus cf. carapo could have facilitated the dispersion of 5S rDNA in these species. Interstitial signals were detected on the first metacentric pair of Gymnotus sylvius by telomeric probes (TTAGGG)n indicating the possible occurrence of chromosomal fusions in this species. The present

  6. Karyotypic diversity in four species of the genus Gymnotus Linnaeus, 1758 (Teleostei, Gymnotiformes, Gymnotidae: physical mapping of ribosomal genes and telomeric sequences

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    Priscilla Scacchetti

    2011-08-01

    Full Text Available Conventional (Giemsa, C-Banding, Ag-NORs, CMA3 and molecular (5S rDNA, 18S rDNA, telomeric sequences cytogenetic studies were carried out in specimens of ten distinct fish populations of the genus Gymnotus (G. sylvius Albert and Fernandes-Matioli, 1999, G. inaequilabiatus Valenciennes, 1839, G. pantherinus Steindachner, 1908, and G. cf. carapo Linnaeus, 1758 from different Brazilian hydrographic basins. G. sylvius presented a diploid number of 40 chromosomes (22m+12sm+6st, G. pantherinus presented 52 chromosomes (32m+18sm+2st, while G. inaequilabiatus (42m+10sm+2a and G. cf. carapo (38m+12sm+4st presented 54 chromosomes. The C-banding technique revealed centromeric marks in all chromosomes of all species. Besides that, conspicuous blocks of heterochromatin were found interstitially on the chromosomes of G. inaequilabiatus, G. cf. carapo, and G. pantherinus. All four species showed single nucleolus organizing regions confirmed by results obtained through Ag-NORs and FISH experiments using 18S rDNA probes, which showed the NORs localized on the first chromosome pair in G. inaequilabiatus, G. cf. carapo, and G. pantherinus, and on pair 2 in G. sylvius. CMA3 staining revealed additional unrelated NORs marks in G. sylvius and G. pantherinus. The 5S rDNA probes revealed signals on one pair in G. sylvius and two pairs in G. pantherinus; G. inaequilabiatus had about seventeen pairs marked, and G. cf. carapo had about fifteen pairs marked. It is considered that the high amount of heterochromatin identified in the chromosomes of G. inaequilabiatus and G. cf. carapo could have facilitated the dispersion of 5S rDNA in these species. Interstitial signals were detected on the first metacentric pair of G. sylvius by telomeric probes (TTAGGGn indicating the possible occurrence of chromosomal fusions in this species. The present study reveals valuable cytotaxonomic markers for this group and allows a more precise evaluation of the processes involved in the

  7. Evolutionary Dynamics of 5S rDNA and Recurrent Association of Transposable Elements in Electric Fish of the Family Gymnotidae (Gymnotiformes): The Case of Gymnotus mamiraua.

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    da Silva, Maelin; Barbosa, Patricia; Artoni, Roberto F; Feldberg, Eliana

    2016-01-01

    Gymnotidae is a family of electric fish endemic to the Neotropics consisting of 2 genera: Electrophorus and Gymnotus. The genus Gymnotus is widely distributed and is found in all of the major Brazilian river systems. Physical and molecular mapping data for the ribosomal DNA (rDNA) in this genus are still scarce, with its chromosomal location known in only 11 species. As other species of Gymnotus with 2n = 54 chromosomes from the Paraná-Paraguay basin, G. mamiraua was found to have a large number of 5S rDNA sites. Isolation and cloning of the 5S rDNA sequences from G. mamiraua identified a fragment of a transposable element similar to the Tc1/mariner transposon associated with a non-transcribed spacer. Double fluorescence in situ hybridization analysis of this element and the 5S rDNA showed that they were colocalized on several chromosomes, in addition to acting as nonsyntenic markers on others. Our data show the association between these sequences and suggest that the Tc1 retrotransposon may be the agent that drives the spread of these 5S rDNA-like sequences in the G. mamiraua genome. © 2016 S. Karger AG, Basel.

  8. Cytogenetic characterization of the strongly electric Amazonian eel, Electrophorus electricus (Teleostei, Gymnotiformes, from the Brazilian rivers Amazon and Araguaia

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    Soraia B.A. Fonteles

    2008-01-01

    Full Text Available A karyotype analysis of the electric eel, Electrophorus electricus (Teleostei, Gymnotiformes, a strongly electric fish from northern South America, is presented. Two female specimens were analyzed, one from the Amazon River and one from the Araguaia River. The specimens had a chromosomal number of 2n = 52 (42M-SM + 10A. C-bands were present in a centromeric and pericentromeric position on part of the chromosomes; some interstitial C-bands were also present. Heteromorphic nucleolus organizer regions (NORs were detected in two chromosome pairs of the specimen from the Amazon River. The chromosome number and karyotype characteristics are similar to those of other Gymnotidae species. The genera Electrophorus and Gymnotus are positioned as the basal lineages in the Gymnotiformes phylogeny.

  9. Dimorfismo sexual em Siluriformes e Gymnotiformes (Ostariophysi da Amazônia Sexual dimorfism in Amazonian Siluriformes and Gymnotiformes (Ostariophysi

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    Lúcia H. Rapp Py-Daniel

    2005-01-01

    Full Text Available No presente trabalho é feito um levantamento dos casos de dimorfismo sexual em Siluriformes e Gymnotiformes. Este levantamento se restringe às formas Neotropicais, com ênfase mais especificamente, às da Amazônia. Peixes dessa região possuem uma grande diversidade, ainda que os limites intraespecíficos não estejam bem definidos. Embora preliminar, o mapeamento de características dimórficas em um cladograma referente a família Loricariidae (Siluriformes auxilia na demonstração de que padrões de dimorfismo sexual são consistentes com hipóteses de monofiletismo. Em Apteronotidae (Gymnotiformes, com base no mapeamento dos caracteres tamanho e forma do focinho e presença de dentes diferenciada em árvores filogenéticas, podemos inferir que esses caracteres originaram-se como eventos independentes em vários táxons. Recentemente, em Gymnotiformes, foram detectados casos de erros taxonômicos atribuídos a diferenças extremas entre machos e fêmeas.The present paper aims to summarize cases of sexual dimorphism in Siluriformes and Gymnotiformes. This summary focuses on Neotropical representatives, with emphasis on Amazonian fish. Fishes from this region exhibit high species-level diversity, although the intraspecific limits of many of these forms are unknown. In Loricariidae (Siluriformes, mapping of dimorphic traits on cladograms has helped to demonstrate that patterns of sex dimorphism are consistent with hypotheses of monophyly, thus reinforcing its role as an important evolutionary phenomenon. In Apteronotidae (Gymnotiformes, mapping of characters on phylogenetic trees suggests that sexual dimorphism (regarding snout size, form, and presence/absence of teeth has evolved independently in multiple taxa. Recently in Gymnotiformes, detected taxonomic errors are attributed to extreme differences between males and females in their morphology.

  10. Neotropical electric fishes (Gymnotiformes as model organisms for bioassays

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    Milena Ferreira

    2015-04-01

    Full Text Available Electric fishes (Gymnotiformes inhabit Central and South America and form a relatively large group with more than 200 species. Besides a taxonomic challenge due to their still unresolved systematic, wide distribution and the variety of habitats they occupy, these fishes have been intensively studied due to their peculiar use of bioelectricity for electrolocation and communication. Conventional analysis of cells, tissues and organs have been complemented with the studies on the electric organ discharges of these fishes. This review compiles the results of 13 bioassays developed during the last 50 years, which used the quickness, low costs and functionality of the bioelectric data collection of Gymnotiformes to evaluate the effects of environmental contaminants and neuroactive drugs.

  11. Hydrodynamic aspects of thrust generation in gymnotiform swimming

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    Shirgaonkar, Anup A.; Curet, Oscar M.; Patankar, Neelesh A.; Maciver, Malcolm A.

    2008-11-01

    The primary propulsor in gymnotiform swimmers is a fin running along most of the ventral midline of the fish. The fish propagates traveling waves along this ribbon fin to generate thrust. This unique mode of thrust generation gives these weakly electric fish great maneuverability cluttered spaces. To understand the mechanical basis of gymnotiform propulsion, we investigated the hydrodynamics of a model ribbon-fin of an adult black ghost knifefish using high-resolution numerical experiments. We found that the principal mechanism of thrust generation is a central jet imparting momentum to the fluid with associated vortex rings near the free edge of the fin. The high-fidelity simulations also reveal secondary vortex rings potentially useful in rapid sideways maneuvers. We obtained the scaling of thrust with respect to the traveling wave kinematic parameters. Using a fin-plate model for a fish, we also discuss improvements to Lighthill's inviscid theory for gymnotiform and balistiform modes in terms of thrust magnitude, viscous drag on the body, and momentum enhancement.

  12. Gymnotus refugio, a new and endangered species of electric fish of the Gymnotus pantherinus species-group from southern Brazil (Gymnotiformes: Gymnotidae).

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    Giora, Julia; Malabarba, Luiz Roberto

    2016-01-19

    Gymnotus refugio, new species, is described from coastal rivers of Rio Grande do Sul and Santa Catarina states, Brazil. It is diagnosed from most species of the Gymnotus pantherinus species-group by the coloration pattern, further differing from G. pantherinus and G. capitimaculatus on the basis of morphometric and meristic characters. The new species represents the most meridional record of the G. pantherinus species-group.

  13. Biochemical and hematological responses of the banded knife fish Gymnotus carapo (Linnaeus, 1758 exposed to environmental hypoxia

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    MORAES G.

    2002-01-01

    Full Text Available Oxygen of tropical freshwater environments fluctuates drastically. Eutrophic lakes and ponds of warm waters frequently reach very low oxygen concentrations. This is the most common habitat of the banded knife fish "tuvira" Gymnotus carapo. This electric fish is reported to present bimodal breathing to cope with low environmental oxygen. Biochemical responses can be also observed in fishes facing hypoxia but none were studied in tuvira. In the present study, haematological and metabolic changes were investigated in two groups of fish exposed to hypoxia for 1 and 3 hours. Haematocrit, red blood cells and haemoglobin concentration indicated erythrocyte release from hematopoietic organs and swelling of red blood cells. Glycogen, glucose, lactate, pyruvate, and amino acids were quantified in liver, kidney and white muscle. The metabolic profile of G. carapo to cope with hypoxia suggested liver gluconeogenesis probably supported by proteolysis. The kidney and liver presented the same biochemical trend suggesting similar metabolic role for both organs. Glucogenolysis followed by glucose fermentation and protein mobilisation was observed in the white muscle. The air breathing behaviour of tuvira works in parallel with metabolism to prevent damages from hypoxia. Metabolic adjustments are observed when the air taking is avoided.

  14. Biochemical and hematological responses of the banded knife fish Gymnotus carapo (Linnaeus, 1758 exposed to environmental hypoxia

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    G. MORAES

    Full Text Available Oxygen of tropical freshwater environments fluctuates drastically. Eutrophic lakes and ponds of warm waters frequently reach very low oxygen concentrations. This is the most common habitat of the banded knife fish "tuvira" Gymnotus carapo. This electric fish is reported to present bimodal breathing to cope with low environmental oxygen. Biochemical responses can be also observed in fishes facing hypoxia but none were studied in tuvira. In the present study, haematological and metabolic changes were investigated in two groups of fish exposed to hypoxia for 1 and 3 hours. Haematocrit, red blood cells and haemoglobin concentration indicated erythrocyte release from hematopoietic organs and swelling of red blood cells. Glycogen, glucose, lactate, pyruvate, and amino acids were quantified in liver, kidney and white muscle. The metabolic profile of G. carapo to cope with hypoxia suggested liver gluconeogenesis probably supported by proteolysis. The kidney and liver presented the same biochemical trend suggesting similar metabolic role for both organs. Glucogenolysis followed by glucose fermentation and protein mobilisation was observed in the white muscle. The air breathing behaviour of tuvira works in parallel with metabolism to prevent damages from hypoxia. Metabolic adjustments are observed when the air taking is avoided.

  15. Reproduction and feeding of the electric fish Brachyhypopomus gauderio (Gymnotiformes: Hypopomidae and the discussion of a life history pattern for gymnotiforms from high latitudes.

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    Julia Giora

    Full Text Available The reproductive biology and feeding habits of the electric fish Brachyhypopomus gauderio were studied. The species has seasonal reproductive behavior, with breeding occurring during the Southern Hemisphere spring and summer, and having a positive relation with the photoperiod variation. Brachyhypopomus gauderio was defined as a fractional spawner, with low relative fecundity and high first maturation size. Sexual dimorphism was registered, males undergoing hypertrophy of the distal portion of caudal filament. The results on reproductive biology herein obtained are in agreement with data concerning gymnotiforms from Southern Brazil and Uruguay, pointing to an ecological pattern for the species from high latitudes, differing from species with tropical distribution. According to the analysis of the food items, B. gauderio feed mainly on autochthonous insects, likewise the other gymnotiforms previously investigated, leading to conclude that there is no variation on the diet of the species of the order related to climatic conditions or even to habitat of occurrence.

  16. FECUNDIDADE E TIPO DE DESOVA DO PORAQUÊ, Electrophorus electricus, (LINNAEUS, 1766 (OSTEICHTHYIES: GYMNOTIFORMES: GYMNOTIDAE DA ÁREA DE PROTEÇÃO AMBIENTAL – APA – DO RIO CURIAÚ, MACAPÁ-AP.

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    Júlio César Sá-Oliveira

    2012-07-01

    Full Text Available O presente estudo objetivou estimar a fecundidade e o tipo de desova do peixe-elétrico Electrophorus electricus da Área de Proteção Ambiental - APA do Rio Curiaú, Macapá-Amapá. As análises foram realizadas a partir de 96 exemplares do peixe coletados no período de março de 2006 a fevereiro de 2007. Análises do ciclo anual de estádios de maturação gonadal, exames macro e microscópico das gônadas, verificação dos diâmetros e contagens dos ovócitos foram realizadas. O número de ovócitos relacionados a uma dimensão corpórea (comprimento total e ao Peso Total (g foi ajustado a uma regressão linear. Os resultados revelaram que a desova é do tipo total e sincrônico, ocorrendo no início do inverno (janeiro-fevereiro. A fecundidade, estimada variou de 1.730 a 3.063 ovócitos vitelogênicos. A fecundidade mostrou correlação positiva com o comprimento total e peso total do corpo, aumentando proporcionalmente com o tamanho de Electrophorus electricus.   Palavras-chave: biologia reprodutiva, Amapá, estádios de maturação gonadal, Brasil.   DOI: http://dx.doi.org/10.18561/2179-5746/biotaamazonia.v2n1p32-36

  17. The untold story of the caudal skeleton in the electric eel (ostariophysi: gymnotiformes: electrophorus.

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    Carlos David de Santana

    Full Text Available Alternative hypotheses had been advanced as to the components forming the elongate fin coursing along the ventral margin of much of the body and tail from behind the abdominal region to the posterior margin of the tail in the Electric Eel, Electrophorus electricus. Although the original species description indicated that this fin was a composite of the caudal fin plus the elongate anal fin characteristic of other genera of the Gymnotiformes, subsequent researchers proposed that the posterior region of the fin was formed by the extension of the anal fin posteriorly to the tip of the tail, thereby forming a "false caudal fin." Examination of ontogenetic series of the genus reveal that Electrophorus possesses a true caudal fin formed of a terminal centrum, hypural plate and a low number of caudal-fin rays. The confluence of the two fins is proposed as an additional autapomorphy for the genus. Under all alternative proposed hypotheses of relationships within the order Gymnotiformes, the presence of a caudal fin in Electrophorus optimized as being independent of the occurence of the morphologically equivalent structure in the Apteronotidae. Possible functional advantages to the presence of a caudal fin in the genus are discussed.

  18. Agonistic-like responses from the torus semicircularis dorsalis elicited by GABA A blockade in the weakly electric fish Gymnotus carapo

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    T.T. Duarte

    2006-07-01

    Full Text Available Findings by our group have shown that the dorsolateral telencephalon of Gymnotus carapo sends efferents to the mesencephalic torus semicircularis dorsalis (TSd and that presumably this connection is involved in the changes in electric organ discharge (EOD and in skeletomotor responses observed following microinjections of GABA A antagonist bicuculline into this telencephalic region. Other studies have implicated the TSd or its mammalian homologue, the inferior colliculus, in defensive responses. In the present study, we explore the possible involvement of the TSd and of the GABA-ergic system in the modulation of the electric and skeletomotor displays. For this purpose, different doses of bicuculline (0.98, 0.49, 0.245, and 0.015 mM and muscimol (15.35 mM were microinjected (0.1 µL in the TSd of the awake G. carapo. Microinjection of bicuculline induced dose-dependent interruptions of EOD and increased skeletomotor activity resembling defense displays. The effects of the two highest doses showed maximum values at 5 min (4.3 ± 2.7 and 3.8 ± 2.0 Hz, P < 0.05 and persisted until 10 min (11 ± 5.7 and 8.7 ± 5.2 Hz, P < 0.05. Microinjections of muscimol were ineffective. During the interruptions of EOD, the novelty response (increased frequency in response to sensory novelties induced by an electric stimulus delivered by a pair of electrodes placed in the water of the experimental cuvette was reduced or abolished. These data suggest that the GABA-ergic mechanisms of the TSd inhibit the neural substrate of the defense reaction at this midbrain level.

  19. The energetics of electric organ discharge generation in gymnotiform weakly electric fish.

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    Salazar, Vielka L; Krahe, Rüdiger; Lewis, John E

    2013-07-01

    Gymnotiform weakly electric fish produce an electric signal to sense their environment and communicate with conspecifics. Although the generation of such relatively large electric signals over an entire lifetime is expected to be energetically costly, supporting evidence to date is equivocal. In this article, we first provide a theoretical analysis of the energy budget underlying signal production. Our analysis suggests that wave-type and pulse-type species invest a similar fraction of metabolic resources into electric signal generation, supporting previous evidence of a trade-off between signal amplitude and frequency. We then consider a comparative and evolutionary framework in which to interpret and guide future studies. We suggest that species differences in signal generation and plasticity, when considered in an energetics context, will not only help to evaluate the role of energetic constraints in the evolution of signal diversity but also lead to important general insights into the energetics of bioelectric signal generation.

  20. Phylogenetic Systematics, Biogeography, and Ecology of the Electric Fish Genus Brachyhypopomus (Ostariophysi: Gymnotiformes.

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    William G R Crampton

    Full Text Available A species-level phylogenetic reconstruction of the Neotropical bluntnose knifefish genus Brachyhypopomus (Gymnotiformes, Hypopomidae is presented, based on 60 morphological characters, approximately 1100 base pairs of the mitochondrial cytb gene, and approximately 1000 base pairs of the nuclear rag2 gene. The phylogeny includes 28 species of Brachyhypopomus and nine outgroup species from nine other gymnotiform genera, including seven in the superfamily Rhamphichthyoidea (Hypopomidae and Rhamphichthyidae. Parsimony and Bayesian total evidence phylogenetic analyses confirm the monophyly of the genus, and identify nine robust species groups. Homoplastic osteological characters associated with diminutive body size and occurrence in small stream habitats, including loss of squamation and simplifications of the skeleton, appear to mislead a phylogenetic analysis based on morphological characters alone-resulting in the incorrect placing of Microsternarchus + Racenisia in a position deeply nested within Brachyhypopomus. Consideration of geographical distribution in light of the total evidence phylogeny indicates an origin for Brachyhypopomus in Greater Amazonia (the superbasin comprising the Amazon, Orinoco and major Guiana drainages, with subsequent dispersal and vicariance in peripheral basins, including the La Plata, the São Francisco, and trans-Andean basins of northwest South America and Central America. The ancestral habitat of Brachyhypopomus likely resembled the normoxic, low-conductivity terra firme stream system occupied by many extant species, and the genus has subsequently occupied a wide range of terra firme and floodplain habitats including low- and high-conductivity systems, and normoxic and hypoxic systems. Adaptations for impedance matching to high conductivity, and/or for air breathing in hypoxic systems have attended these habitat transitions. Several species of Brachyhypopomus are eurytopic with respect to habitat occupancy and

  1. Systematics and biogeography of Sternarchellini (Gymnotiformes: Apteronotidae: Diversification of electric fishes in large Amazonian rivers

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    Stephen J. Ivanyisky III

    Full Text Available The Sternarchellini (Gymnotiformes, Apteronotidae is a clade of 10 electric fish species that inhabit deep river channels of the Amazon and Orinoco basins, attain moderate adult body sizes (15-50 cm TL, and have a predatory life style. Here we trace the evolutionary origin and diversification of Sternarchellini using standard phylogenetic and biogeographic procedures and a dataset of 70 morphological characters. The main results are: 1 the genus Sternarchellaincludes both species currently assigned to the genus Magosternarchus; and 2 neither of the multi-species assemblages of Sternarchellini in the Amazon and Orinoco basins are monophyletic. Historical biogeographic analysis suggests that sternarchelline evolution was linked to the large-scale river capture event that formed the modern Amazon and Orinoco basins, i.e. the Late Miocene rise of the Vaupes structural arch and concomitant breaching of the Purus structural arch. This event is hypothesized to have contributed to formation of the modern sternarchelline species, and to the formation of the modern basin-wide sternarchelline species assemblages. The results indicate that cladogenesis (speciation and anagenesis (adaptive evolution were decoupled processes in the evolution of Sternarchellini.

  2. X1X1X2X2/X1X2Y sex chromosome systems in the Neotropical Gymnotiformes electric fish of the genus Brachyhypopomus

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    Adauto Lima Cardoso

    2015-06-01

    Full Text Available Several types of sex chromosome systems have been recorded among Gymnotiformes, including male and female heterogamety, simple and multiple sex chromosomes, and different mechanisms of origin and evolution. The X1X1X2X2/X1X2Y systems identified in three species of this order are considered homoplasic for the group. In the genus Brachyhypopomus, only B. gauderio presented this type of system. Herein we describe the karyotypes of Brachyhypopomus pinnicaudatus and B. n. sp. FLAV, which have an X1X1X2X2/X1X2Y sex chromosome system that evolved via fusion between an autosome and the Y chromosome. The morphology of the chromosomes and the meiotic pairing suggest that the sex chromosomes of B. gauderio and B. pinnicaudatus have a common origin, whereas in B . n. sp. FLAV the sex chromosome system evolved independently. However, we cannot discard the possibility of common origin followed by distinct processes of differentiation. The identification of two new karyotypes with an X1X1X2X2/X1X2Y sex chromosome system in Gymnotiformes makes it the most common among the karyotyped species of the group. Comparisons of these karyotypes and the evolutionary history of the taxa indicate independent origins for their sex chromosomes systems. The recurrent emergence of the X1X1X2X2/X1X2Y system may represent sex chromosomes turnover events in Gymnotiformes.

  3. Evolution of electric communication signals in the South American ghost knifefishes (Gymnotiformes: Apteronotidae): A phylogenetic comparative study using a sequence-based phylogeny.

    Science.gov (United States)

    Smith, Adam R; Proffitt, Melissa R; Ho, Winnie W; Mullaney, Claire B; Maldonado-Ocampo, Javier A; Lovejoy, Nathan R; Alves-Gomes, José A; Smith, G Troy

    2016-10-01

    The electric communication signals of weakly electric ghost knifefishes (Gymnotiformes: Apteronotidae) provide a valuable model system for understanding the evolution and physiology of behavior. Apteronotids produce continuous wave-type electric organ discharges (EODs) that are used for electrolocation and communication. The frequency and waveform of EODs, as well as the structure of transient EOD modulations (chirps), vary substantially across species. Understanding how these signals have evolved, however, has been hampered by the lack of a well-supported phylogeny for this family. We constructed a molecular phylogeny for the Apteronotidae by using sequence data from three genes (cytochrome c oxidase subunit 1, recombination activating gene 2, and cytochrome oxidase B) in 32 species representing 13 apteronotid genera. This phylogeny and an extensive database of apteronotid signals allowed us to examine signal evolution by using ancestral state reconstruction (ASR) and phylogenetic generalized least squares (PGLS) models. Our molecular phylogeny largely agrees with another recent sequence-based phylogeny and identified five robust apteronotid clades: (i) Sternarchorhamphus+Orthosternarchus, (ii) Adontosternarchus, (iii) Apteronotus+Parapteronotus, (iv) Sternarchorhynchus, and (v) a large clade including Porotergus, 'Apteronotus', Compsaraia, Sternarchogiton, Sternarchella, and Magosternarchus. We analyzed novel chirp recordings from two apteronotid species (Orthosternarchus tamandua and Sternarchorhynchus mormyrus), and combined data from these species with that from previously recorded species in our phylogenetic analyses. Some signal parameters in O. tamandua were plesiomorphic (e.g., low frequency EODs and chirps with little frequency modulation that nevertheless interrupt the EOD), suggesting that ultra-high frequency EODs and "big" chirps evolved after apteronotids diverged from other gymnotiforms. In contrast to previous studies, our PGLS analyses using the

  4. Previously undescribed dental arrangement among electric knifefishes, with comments on the taxonomic and conservation status of Tembeassu marauna Triques (Otophysi: Gymnotiformes: Apteronotidae

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    Ricardo Campos-da-Paz

    Full Text Available Recent study of the type-material of Tembeassu marauna, a poorly-known species currently represented in collections only by its holotype (male and paratypes (male and female, all collected forty years ago at the Ilha Solteira reservoir area, upper Paraná river region, revealed an unique pattern of dental arrangement among members of the order Gymnotiformes. This autapomorphic condition refers to a patch of around 15 elongate conical, extra teeth associated to soft tissue, and disposed inside the mouth on a restricted area at the roof of oral cavity and located just in front of the premaxillary bones (although clearly apart from those. Besides this obvious feature, two additional conditions are recognized as possibly unique for T. marauna, which refer to the conspicuous "fleshy" (that is, not presenting subjacent bony structures anterior elongations of the upper and lower jaws. Some additional osteological features identified on radiographs taken from the type material belonging to that species are presented. A brief discussion is furnished, indicating that the recent inclusion of the nominal Tembeassu marauna in Apteronotus La Cépède is not supported by currently available evidence. Thus, it is herein suggested that the species is kept in it own separate genus within the Apteronotidae. Finally, it is argued that T. marauna possibly represents an endangered species at the upper Paraná river region.

  5. Two new species and a new subgenus of toothed Brachyhypopomus electric knifefishes (Gymnotiformes, Hypopomidae) from the central Amazon and considerations pertaining to the evolution of a monophasic electric organ discharge.

    Science.gov (United States)

    Sullivan, John P; Zuanon, Jansen; Cox Fernandes, Cristina

    2013-01-01

    We describe two new, closely related species of toothed Brachyhypopomus (Hypopomidae: Gymnotiformes: Teleostei) from the central Amazon basin and create a new subgenus for them. Odontohypopomus, new subgenus of Brachyhypopomus, is diagnosed by (1) small teeth present on premaxillae; (2) medialmost two branchiostegal rays thin with blades oriented more vertically than remaining three rays; (3) background color in life (and to lesser extent in preservation) distinctly yellowish with head and sides peppered with small, widely spaced, very dark brown stellate chromatophores that greatly contrast with light background coloration; (4) a dark blotch or bar of subcutaneous pigment below the eye; (5) electric organ discharge waveform of very long duration (head-positive phase approx. 2 milliseconds or longer, head-negative phase shorter or absent) and slow pulse repetition rate (3-16 Hz). The type species of the new subgenus, Brachyhypopomus (Odontohypopomus) walteri sp. n., is diagnosed by the following additional character states: (1) subcutaneous dark pigment at base of orbit particularly prominent, (2) body semi-translucent and nearly bright yellow background coloration in life, (3) a biphasic electric organ discharge (EOD) waveform of very long duration (between 3.5 and 4 milliseconds at 25° C) with head-positive first phase significantly longer than second head-negative phase in both sexes. Brachyhypopomus (Odontohypopomus) bennetti sp. n. is diagnosed by two character states in addition to those used to diagnose the subgenus Odontohypopomus: (1) a deep electric organ, visible as large semi-transparent area, occupying approximately 14-17% body depth directly posterior to the abdominal cavity in combination with a short, but deep, caudal filament, and (2) a monophasic, head-positive EOD waveform, approximately 2.1 milliseconds in duration in both sexes. These are the only described rhamphichthyoid gymnotiforms with oral teeth, and Brachyhypopomus bennetti is the first

  6. Effects of Neuroactive Drugs in the Discharge Patterns of Microsternarchus (Hypopomidae: Gymnotiformes) Electric Organ.

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    de Jesus, Isac Silva; Ferreira, Milena; Silva-Júnior, Urbano Lopes; Alves-Gomes, José Antônio

    2017-12-01

    Considering the conserved nature of synaptic physiology among vertebrates, we tested the effects of three psychotropics (diazepam, doxapram, and nicotine) on Microsternarchus cf. bilineatus, measuring 10 parameters associated to the electric organ discharges rhythm and waveform before and after the administration of each drug and a control group. There were statistically significant differences (p electric organ's (EO) firing rate, regardless of the expected stimulant or depressor effect of the drugs on the central nervous system (CNS). The intensity of the response changed with the treatment. The observed changes in the fishes' behavior may be a result of the drugs' direct action on the CNS or a combination of this with systemic effects of each substance tested, also in the EO.

  7. Diversity of neotropical electric fish Microsternarchus (Teleostei: Gymnotiformes: Hypopomidae: an electrophysiological and geometric morphometric approach

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    Adília Nogueira

    2015-11-01

    Full Text Available The South American hypopomid electric fish tribe Microsternarchini includes three small species from the Upper Orinoco and Negro rivers. These are placed in monotypic genera: Microsternarchus, Racenisia and Procerusternarchus. Recent collections from tributaries in Negro, Solimões and Amazonas Basins have revealed new specimens of Microsternarchus with significant variations in external morphology and in Electric Organ Discharge parameters (EOD. In order to estimate the diversity within the genus a previous molecular study was done using DNA barcoding, that suggested the presence of multiple Microsternarchus's lineages with high levels of genetic divergence between them. Here we try to determine if the variation in morphology and EOD parameters in the new specimens meet the genetic divergence found. To test the presence of differences in shape among the different lineages we performed a geometric morphometric analysis, which included a relative warp and multivariate analysis on distances between 14 anatomical landmarks defined on the basis of external morphology and homologous among the lineages. The EOD variations were also explored using multivariate analyses of 20 electrophysiological parameters calculated through an algorithm developed in Matlab. The results show that there are significant differences in body shape and EOD in three lineages of Microsternarchus, and the features that contributed most were related to the shape of the head, the coefficient of variation of the signal and the duration and area of the different phases of the pulse. The discrimination of the three lineages confirms the occurrence of new species in the group that are currently being described.

  8. Karyotypic similarities between two species of Rhamphichthys (Rhamphichthyidae, Gymnotiformes from the Amazon basin

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    Patrícia Silva

    2013-10-01

    Full Text Available The family Rhamphichthyidae includes three genera: Rhamphichthys Müller et Troschel, 1846, Gymnorhamphichthys M. M. Ellis, 1912 and Iracema Triques, 1996. From this family, only the species Rhamphichthys hanni Meinken, 1937 has had its karyotype described. Here, we describe the karyotypes of two additional Rhamphichthys species: R. marmoratus Castelnau, 1855 from the Reserva de Desenvolvimento Sustentável Mamirauá, Amazonas state and R. prope rostratus Linnaeus, 1766 from Pará state, both in Brazil. Our karyotypic analyses demonstrated that the diploid number is conserved for the genus (2n = 50, but the karyotypic formulas (KFs differed between R. marmoratus (44m/sm+6a and R. prope rostratus (42m/sm+8a. In both species, the constitutive heterochromatin (CH was located in the centromeric region of most chromosomes. Large heterochromatic blocks were found on the long arms of pairs 4 and 14 in R. marmoratus and on chromosomes 3, 4 and 19 in R. prope rostratus, which also has a heteromorphism in chromosome pair 1. The CH was DAPI positive, indicating that it is rich in AT base pairs. The Nucleolus Organizer Region (NOR showed staining at a single location in both species: the long arm of pair 1 in R. marmoratus and the long arm of pair 12 in R. prope rostratus, where it showed a size heteromorphism. CMA3 staining coincided with that of Ag-NOR, indicating that the ribosomal genes contain interspaced GC-rich sequences. FISH with an 18S rDNA probe confirmed that there is only one NOR site in each species. These results can be used as potential cytogenetic markers for fish populations, and comparative analysis of the karyotypes of Hypopygus Hoedman, 1962, Rhamphichthys and Steatogenys Boulenger, 1898 suggests that the first two genera diverged later that the third.

  9. The contribution of air breathing to aerobic scope and exercise performance in the banded knifefish Gymnotus carapo L

    DEFF Research Database (Denmark)

    McKenzie, David J.; Steffensen, John Fleng; Taylor, Edwin W.

    2012-01-01

    , these individuals achieved a U(crit) of 2.0±0.2 BL s(-1) and an AMR of 368±24 mg kg(-1) h(-1) by gill ventilation alone. In normoxia, therefore, the contribution of air breathing to scope and exercise was entirely facultative. In aquatic hypoxia (P(O(2))=4 kPa) with access to normoxic air, the knifefish achieved...... a U(crit) of 2.0±0.1 BL s(-1) and an AMR of 338±29 mg kg(-1) h(-1), similar to aquatic normoxia, but with 55±5% of AMR derived from air breathing. Indeed, f(AB) was higher than in normoxia at all swimming speeds, with a profound exponential increase during exercise. If the knifefish were denied access...... to air in hypoxia, U(crit) declined to 1.2±0.1 BL s(-1) and AMR declined to 199±29 mg kg(-1) h(-1). Therefore, air breathing allowed the knifefish to avoid limitations to aerobic scope and exercise performance in aquatic hypoxia....

  10. Avaliação da mutagênese e genotoxicidade em Eigenmannia virescens (Teleostei: Gymnotiformes expostos ao benzeno Avaliation of mutagenicity and gentotoxicity in Eigenmannia virescens (Teleostei: Gymnotiformes exposed to benzene

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    Augusto Bücker

    2006-01-01

    Full Text Available Os efeitos de substâncias genotóxicas sobre o genoma de peixes tem sido objeto de muitos estudos, sobretudo daqueles que buscam estabelecer a resposta dos genes aos estímulos ambientais. O presente trabalho teve como objetivo realizar um estudo sobre mutagenicidade e genotoxicidade em peixes elétricos da espécie Eingenmannia virescens, pela exposição ao benzeno (50ppm, utilizando as técnicas da Freqüência de Micronúcleos (MNs e o Ensaio do Cometa. Foram coletadas amostras do sangue de dez peixes em diferentes tempos de exposição: T0, 24h, 48h, 72h, 96h e 360h (15 dias. Para a análise das lâminas no Teste do MN, foram contadas 1.000 células e estipulada a freqüência de ocorrência de MNs. Para análise do Ensaio do Cometa a contagem foi feita estipulando quatro classes de danos: I - II - III - IV, e para a análise estatística foram atribuídos valores numéricos (ranques de 0 a 3, respectivamente, verificando diferenças significativas para a soma dos ranques em todos os tempos de exposição em relação ao T0. No Teste do Micronúcleo não foi possível detectar efeitos mutagênicos significativos nos eritrócitos analisados. No entanto, para o Ensaio do Cometa os resultados sugerem ação genotóxica do benzeno, devido a um aumento gradual no número de células com maiores classes de danos de acordo com maior tempo de exposição, indicando um efeito tempo-dependente. Estes resultados sugerem maior sensibilidade do Ensaio do Cometa que o Teste do MN.The effects of genotoxic substances on fishes genome have been object of many studies, especially those which attempt to establish the responses of genes to environmental stimulus. The objective of this study was to evaluate the mutagenicity and genotoxicity in electric fishes of species Eingenmannia virescens, under to benzene exposure (50ppm, utilizing Micronuclei Test (MNs and Comet Assay techniques. Ten fish blood samples were collected in different times of exposure: T0, 24h, 48h, 72h, 96h and 360h (15 days. To determine the frequency of MNs, 1.000 cells per microscopical slides were counted. For the Comet Assay analysis, four damage classes were defined: I - II - III - IV, and for the statistic analysis number values (ranks from 0 to 3 were assigned for each class. The sum of ranks (values for all times of exposure was compared to T0 and these differences were statistically analyzed. On Micronuclei Test demonstrated do not possible detect significant mutagenic effects in the erythrocytes analyzed. On the other hand, for the Comet Assay, the results suggested genotoxic action of benzene, proper the gradual increase of number of cells with greatest damage class with the greatest of exposure time, indicating an effect time-dependent. These results suggested the most sensibility for the Comet Assay like Micronuclei Test.

  11. A taxonomic revision of the Neotropical electric fish genus Brachyhypopomus (Ostariophysi: Gymnotiformes: Hypopomidae, with descriptions of 15 new species

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    William G. R. Crampton

    Full Text Available ABSTRACT The bluntnose knifefish genus BrachyhypopomusMago-Leccia, 1994, is diagnosed from other Rhamphichthyoidea (Rhamphichthyidae + Hypopomidae by the presence of a disk-like ossification in the anterior portion of the palatoquadrate, and by the following external characters: short snout, 18.7-32.6% of head length (vs. 33.3-68.6% in Hypopomus, Gymnorhamphichthys, Iracema, and Rhamphichthys, absence of a paired accessory electric organ in the mental or humeral region (vs. presence in Hypopygus and Steatogenys, presence of 3-4 pectoral proximal radials (vs. 5 in Akawaio, presence of the antorbital + infraorbital, and the preopercular cephalic lateral line canal bones (vs. absence in Racenisia. Brachyhypopomus cannot be diagnosed unambiguously from Microsternarchus or from Procerusternarchus on the basis of external characters alone. Brachyhypopomus comprises 28 species. Here we describe 15 new species, and provide redescriptions of all 13 previously described species, based on meristic, morphometric, and other morphological characters. We include notes on ecology and natural history for each species, and provide regional dichotomous keys and distribution maps, based on the examination of 12,279 specimens from 2,787 museum lots. A lectotype is designated for Brachyhypopomus pinnicaudatus (Hopkins, Comfort, Bastian & Bass, 1990. Brachyhypopomus species are abundant in shallow lentic and slow-flowing freshwater habitats from southern Costa Rica and northern Venezuela to Uruguay and northern Argentina. Species diversity is highest in Greater Amazonia, where 20 species occur: B. alberti, new species, B. arrayae, new species, and B. cunia, new species, in the upper rio Madeira drainage; B. batesi, new species, in the central Amazon and rio Negro; B. beebei, B. brevirostris, B. regani, new species, B. sullivani, new species, and B. walteri, widespread through the Amazon and Orinoco basins and the Guianas; B. belindae, new species, in the central Amazon basin; B. benjamini, new species, and B. verdii, new species, in the upper Amazon basin; B. bennetti, in the upper, central, and lower Amazon, lower Tocantins, and upper Madeira basins; B. bullocki in the Orinoco, Negro and Essequibo drainages; B. diazi in the Orinoco Llanos; B. flavipomus, new species, and B. hamiltoni, new species, in the central and upper Amazon basin; B. hendersoni, new species, in the central Amazon, lower Negro and Essequibo basins; B. pinnicaudatus in the central and lower Amazon, lower, upper Madeira, lower Tocantins and Mearim basins, and coastal French Guiana; and B. provenzanoi, new species, in the upper Orinoco and upper Negro basins. Five species are known from the Paraná-Paraguay-Uruguay basin and adjacent southern Atlantic drainages: B. bombilla in the lower Paraná, upper, central, and lower Paraguay, Uruguay and Patos-Mirim drainages; B. brevirostris in the upper Paraguay basin; B. draco in the lower Paraná, lower Paraguay, Uruguay, Patos-Mirim, and Tramandaí basins; B. gauderio in the lower Paraná, upper, central, and lower Paraguay, Uruguay, Patos-Mirim and Tramandaí basins; and B. walteri in the lower Paraná and upper Paraguay basins. Two species occur in small Atlantic drainages of southern Brazil: B. janeiroensis in the São João, Paraíba and small intervening drainages; and B. jureiae in the Ribeira de Iguape and Una do Prelado. One species occurs in the middle and upper São Francisco basin: B. menezesi, new species. Three species occur in trans-Andean drainages: B. diazi in Caribbean drainages of northern Venezuela; B. occidentalis in Atlantic and Pacific drainages of southern Costa Rica and Panama to Darién, and the Maracaibo, Magdalena, Sinú and Atrato drainages; and B. palenque, new species, in Pacific drainages of Ecuador.

  12. A new vision of the origin and the oocyte development in the Ostariophysi applied to Gymnotus sylvius (Teleostei: Gymnotiformes

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    Gisleine Fernanda França

    Full Text Available Based on new knowledge coming from marine perciform species, the origin of oocytes and their development in the Ostariophysi, Gymnotus sylvius is described. In both Gymnotus sylvius and marine perciform fish, oogonia are found in the germinal epithelium that forms the surface of the ovarian lamellae. At the commencement of folliculogenesis, proliferation of oogonia and their entrance into meiosis gives rise to germ cell nests that extend into the stroma from the germinal epithelium. Both cell nests and the germinal epithelium are supported by the same basement membrane that separates them from the stroma. At the time of meiotic arrest, oocytes in a cell nest become separated one from the other as processes of prefollicle cells, these being derived from epithelial cells in the germinal epithelium, gradually encompass and individualize them while also synthesizing a basement membrane around themselves during folliculogenesis. The oocyte enters primary growth while still within the cell nest. At the completion of folliculogenesis, the oocyte and follicle cells, composing the follicle, are encompassed by a basement membrane. The follicle remains connected to the germinal epithelium as the both share a portion of common basement membrane. Cells originating from the stroma encompass the ovarian follicle, except where there is a shared basement membrane, to form the theca. The follicle, basement membrane and theca form the follicular complex. Oocyte development occurs inside the follicular complex. Development is divided into the stages primary and secondary growth, oocyte maturation and ovulation. Cortical alveoli appear in the ooplasm just prior to the beginning of secondary growth, the vitellogenic stage that begins with yolk deposition and proceeds until the oocyte is full-grown and the ooplasm is filled with yolk globules. Maturation is characterized by the germinal vesicle or nuclear migration, germinal vesicle breakdown or nuclear envelop fragmentation and the resumption of meiosis. At the ovulation the egg is released from the follicular complex into the ovarian lumen. When compared to marine Perciformes that lay pelagic eggs, oocyte development in Gymnotus sylvius has fewer steps within the stages of development, the two most remarkable being the absence of oil droplet formation during primary and secondary growth, (and the consequent absence of the oil droplets fusion during maturation, and the hydrolysis of yolf preceding ovulation.

  13. Composição e estrutura das infracomunidades endoparasitárias de Gymnotus spp. (Pisces: Gymnotidae do rio Baía, Mato Grosso do Sul, Brasil - DOI: 10.4025/actascibiolsci.v26i4.1527 Composition and structure of the endoparasite infracommunities of Gymnotus spp. (Pisces: Gymnotidae of the Baía River, Mato Grosso do Sul, Brazil - DOI: 10.4025/actascibiolsci.v26i4.1527

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    Gilberto Cezar Pavanelli

    2004-04-01

    Full Text Available Foram examinados 111 espécimes do gênero Gymnotus. Os peixes foram capturados em peneiras e redes de espera. Foram registradas dezesseis espécies de helmintos, estando 93,7% delas em fase larval. Ocorreram associações positivas significativas entre vinte pares de espécies de parasitas. Todas elas apresentaram um padrão de distribuição agregada na amostra de hospedeiros. Não houve tendência para dominância entre as espécies de parasitas. Hospedeiros machos e fêmeas não apresentaram diferenças significativas entre as diversidades parasitárias, mas houve influência do sexo dos hospedeiros sobre a prevalência e abundância de infecção de Tylodelphys sp. e Spiroxys sp.. Foi observado correlação positiva significativa entre o comprimento total dos hospedeiros e a prevalência e a abundância de infecção de Nomimoscolex chubbi, Contracaecum sp. 2 e Quadrigyrus machadoi. Houve relação significativa entre a prevalência de Herpetodiplostomum sp. 1, Herpetodiplostomum sp. 3, Neodiplostomum sp. e Tylodelphys sp. e o ciclo reprodutivo dos hospedeirosParasites of 111 specimens of the Gymnotus genus were analyzed. The fishes were captured in bolters and gill nets. Sixteen parasite species were recorded, being 93.7% of the species found in larval stages. Significant positive association and correlation between abundances of twenty pairs of species occurred. All the analyzed parasite species had a clumped pattern in host sample. No dominance was reported among the parasite species. Diversity of the infracommunities of male and female hosts were not different, but influence of hosts' sex in the prevalence and abundance of Tylodelphys sp. and Spiroxys sp. were observed. Significant positive correlation between hosts' total length and prevalence and abundance of Nomimoscolex chubbi, Contracaecum sp. 2 and Quadrigyrus machadoi was observed. The reproductive cycle of hosts was correlated with the Herpetodiplostomum sp. 1, Herpetodiplostomum sp. 3, Neodiplostomum sp. and Tylodelphys sp. prevalences

  14. Hypopomus Gill: nova apomorfia e notas sobre suas relações filogenéticas (Teleostei, Gymnotiformes, Rhamphichthyoidea Hypopomus Gill: new apomorphy and notes on its phylogenetic relationships (Teleostei, Gymnotioformes, Rhamphichthoidea

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    Mauro L. Triques

    2007-01-01

    Full Text Available O monofiletismo de Hypopomus Gill, 1864 é corroborado pela presença de canto da boca curvo para cima, homoplasticamente também em Steatogenys Boulenger, 1898. Sua sinonímia com Parupygus Hoedeman, 1962 é corroborada. Três de sete apomorfias previamente atribuídas para definir o monofiletismo de Hypopomidae são refutadas (região posterior do paresfenóide estreita, depressão na face dorsal do basi-hial e opérculo trapezoidal e outras quatro são propostas para unir Hypopomus a Rhamphichthyidae (mandíbula incluída; alongamento anterior do dentário; cartilagem palatina alongada e processo ascendente do mesopterigóide curvo para trás. Assim, estudos mais elaborados são necessários para avaliar a posição filogenética do gênero.The monophyly of Hypopomus Gill, 1864 is corroborated, on the basis of the presence of mouth corner upturned, homoplastically also in Steatogenys Boulenger, 1898. Its synonymy with Parupygus Hoedeman, 1962 is corroborated. Three of seven synapomorphies attributed to the monophyly of Hypopomidae are refuted (posterior region of parasphenoid narrow, depression on the dorsal surface of bashyal and trapezoidal opercle and four other are presented to unite Hypopomus to Rhamphichthyidae (lower jaw included; anterior elongation of dentary; elongation of palatine cartilage and ascending process of mesopterygoid backward curved. Thus, further studies are necessary to assess the phylogenetic position of the genus.

  15. Composição em tamanho dos peixes (Actinopterygii, Teleostei de ribeirões da bacia do rio Tibagi, Paraná, Brasil

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    Shibatta Oscar A.

    2003-01-01

    Full Text Available The standard length of 7610 specimens of 43 species from eight streams of rio Tibagi basin was obtained in order to analyze the means of fish sizes. The higher mean size was observed in Gymnotus carapo Linnaeus, 1758 (165,5 mm and the smaller, in Phalloceros caudimaculatus (Hensel, 1868 (16,25 mm. Some fish like Acestrorhynchus lacustris (Reinhardt, 1874, Leporinus obtusidens (Valenciennes, 1836, Gymnotus carapo Linneus, 1758 and Synbranchus marmoratus Bloch, 1795 can reach big or medium size when adults but were collected only young, evidencing they use some streams in beginning of life. The mean size of total species was 49,81mm, what shows the small size composition of fishes in the streams. The Kolmogov-Smirnov test comparing the mean size of all streams showed significant similar size both in upstream and downstream regions, independent to the different environmental conditions.

  16. The complete mitochondrial genome of the helmet catfish Cranoglanis bouderius (Siluriformes: Cranoglanididae) and the phylogeny of otophysan fishes

    DEFF Research Database (Denmark)

    Peng, Zuogang; Wang, Jun; He, Shunping

    2006-01-01

    the approximately unbiased test, the Kishino-Hasegawa test, and the Shimodaira-Hasegawa test. The results show that the grouping ((((Characiformes, Gymnotiformes), Siluriformes), Cypriniformes), outgroup) is the most likely but there is no significant difference between this one and the other alternative hypotheses...

  17. Higher and lower-level relationships of the deep-sea fish order Alepocephaliformes (Teleostei: Otocephala) inferred from whole mitogenome sequences

    DEFF Research Database (Denmark)

    Poulsen, Jan Yde; Møller, Peter Rask; Lavoué, Sébastien

    2009-01-01

    , Cypriniformes, Characiformes, Siluriformes and Gymnotiformes). The disputed family Bathylaconidae was found to be an artificial assemblage of the two genera Bathylaco and Herwigia, with the former as the sister group of the family Alepocephalidae and the latter nested within Alepocephalidae. Platytroctidae...

  18. Comparable ages for the independent origins of electrogenesis in African and South American weakly electric fishes.

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    Sébastien Lavoué

    Full Text Available One of the most remarkable examples of convergent evolution among vertebrates is illustrated by the independent origins of an active electric sense in South American and African weakly electric fishes, the Gymnotiformes and Mormyroidea, respectively. These groups independently evolved similar complex systems for object localization and communication via the generation and reception of weak electric fields. While good estimates of divergence times are critical to understanding the temporal context for the evolution and diversification of these two groups, their respective ages have been difficult to estimate due to the absence of an informative fossil record, use of strict molecular clock models in previous studies, and/or incomplete taxonomic sampling. Here, we examine the timing of the origins of the Gymnotiformes and the Mormyroidea using complete mitogenome sequences and a parametric bayesian method for divergence time reconstruction. Under two different fossil-based calibration methods, we estimated similar ages for the independent origins of the Mormyroidea and Gymnotiformes. Our absolute estimates for the origins of these groups either slightly postdate, or just predate, the final separation of Africa and South America by continental drift. The most recent common ancestor of the Mormyroidea and Gymnotiformes was found to be a non-electrogenic basal teleost living more than 85 millions years earlier. For both electric fish lineages, we also estimated similar intervals (16-19 or 22-26 million years, depending on calibration method between the appearance of electroreception and the origin of myogenic electric organs, providing rough upper estimates for the time periods during which these complex electric organs evolved de novo from skeletal muscle precursors. The fact that the Gymnotiformes and Mormyroidea are of similar age enhances the comparative value of the weakly electric fish system for investigating pathways to evolutionary novelty

  19. Influences on Group Productivity 1: Factors Inherent in the Task. A bibliographic Synopsis

    Science.gov (United States)

    1983-04-15

    ut- ue Urer~i y, Peter E. Carapos, University ,of Hawaii at Maanoa Arthur Irving, Indiana University--Purdue University Dan Landis, Indiana...aooreciatir, tc t’.’e staff :,-0 t-.e East- West Center and to Professor Neal Goodman St t.£t. Peters -.--!ese for their invaluaole a.d in t-e pre~arz,t...behavior: coded or standard- zec code. Ŕ I- STP ... DEPEDET MEASURES i Seta, Paulus & Schkade, 1976 1. n of correct words recalled. Shaw & Aston, 1976 1

  20. Directory of Open Access Journals (Sweden)

    Jonathan W. Armbruster

    2013-03-01

    Full Text Available Neblinichthys peniculatus is described from specimens collected in the río Carapo (río Paragua - río Caroni drainage, which drains the southern flank of Cerro Guaiquinima in southeastern Venezuela. Neblinichthys peniculatus differs from all congeners by having mottling on the caudal peduncle consisting of dark spots and dashes (vs. caudal peduncle all about the same color or light below and dark above and by having spots on the head (spots less conspicuous in nuptial males as the head is darker; vs. no spots. Uniquely among Neblinichthys for which nuptial males are known, the hypertrophied odontodes on the snout are rather short, none as large as the eye diameter.Se describe una nueva especie, Neblinichthys peniculatus, con especímenes colectados del río Carapo (cuenca del río Paragua-rio Caroní, que drena el flanco sur del Cerro Guaiquinima en el sureste de Venezuela. Neblinichthys peniculatus difiere de todos sus congéneres en tener un patrón de pigmentación moteado en el pedúnculo caudal, que consiste de puntos y líneas cortas oscuras (vs. pedúnculo caudal más o menos uniformemente pigmentado, más oscuro dorsalmente y más claro ventralmente y por tener puntos en la cabeza (los puntos son menos conspicuos en los machos nupciales; vs. cabeza sin puntos. Los odontodos hipertrofiados del hocico son cortos en los machos nupciales y ninguno es tan largo como el diámetro del ojo, una condición única entre las especies de Neblinichthys de las cuales se conocen los machos nupciales.

  1. Hydrogen-Assisted IC Engine Combustion as a Route to Hydrogen Implementation

    Energy Technology Data Exchange (ETDEWEB)

    Andre Boehman; Daniel Haworth

    2008-09-30

    The 'Freedom Car&apos; Initiative announced by the Bush Administration has placed a significant emphasis on development of a hydrogen economy in the United States. While the hydrogen-fueled fuel-cell vehicle that is the focus of the 'Freedom Car&apos; program would rely on electrochemical energy conversion, and despite the large amount of resources being devoted to its objectives, near-term implementation of hydrogen in the transportation sector is not likely to arise from fuel cell cars. Instead, fuel blending and ''hydrogen-assisted'' combustion are more realizable pathways for wide-scale hydrogen utilization within the next ten years. Thus, a large potential avenue for utilization of hydrogen in transportation applications is through blending with natural gas, since there is an existing market for natural-gas vehicles of various classes, and since hydrogen can provide a means of achieving even stricter emissions standards. Another potential avenue is through use of hydrogen to 'assist' diesel combustion to permit alternate combustion strategies that can achieve lower emissions and higher efficiency. This project focused on developing the underlying fundamental information to support technologies that will facilitate the introduction of coal-derived hydrogen into the market. Two paths were envisioned for hydrogen utilization in transportation applications. One is for hydrogen to be mixed with other fuels, specifically natural gas, to enhance performance in existing natural gas-fueled vehicles (e.g., transit buses) and provide a practical and marketable avenue to begin using hydrogen in the field. A second is to use hydrogen to enable alternative combustion modes in existing diesel engines, such as homogeneous charge compression ignition, to permit enhanced efficiency and reduced emissions. Thus, this project on hydrogen-assisted combustion encompassed two major objectives: (1) Optimization of hydrogen-natural gas mixture

  2. A massive invasion of fish species after eliminating a natural barrier in the upper rio Paraná basin

    Directory of Open Access Journals (Sweden)

    Horácio Ferreira Júlio Júnior

    Full Text Available Based on long-term studies in the upper rio Paraná basin, in addition to a broad review of literature and other information, we were able to identify 33 species of native fishes in the lower rio Paraná basin that successfully colonized the upper rio Paraná after Itaipu impoundment, that flooded the natural geographic barrier constituted by the Sete Quedas Falls. These species belong to six Orders, encompassing two of Myliobatiformes, six of Characiformes, 17 of Siluriformes, six of Gymnotiformes, one of Perciformes, and one of Pleuronectiformes. Extensive remarks regarding each species, including their influence upon the native assemblage, in addition to comments on other non-indigenous species, are also provided. We conclude that, in spite of its widespread neglected by environmental impact studies, massive invasion of species is a real possibility when natural barriers are suppressed by reservoirs.

  3. Fallen leaves on the water-bed: diurnal camouflage of three night active fish species in an Amazonian streamlet

    Directory of Open Access Journals (Sweden)

    Ivan Sazima

    Full Text Available Resemblance to dead leaves is a well known type of camouflage recorded for several small vertebrates that dwell in the leaf and root litter on the ground. We present here instances of such resemblance in three species of nocturnal fishes (Siluriformes and Gymnotiformes that spend the daytime among submersed root-tangle with leaf litter in Amazonian streams. All three species are very difficult to spot visually, due both to their shape and colors which blend with the substrate, as well as to the heterogeneous nature of their cover. Two species were recorded to lie on their sides, which adds to their resemblance to dead leaves. When disturbed, one species may drift like a waterlogged leaf, whereas another moves upwards the root-tangle, exposing its fore body above the water surface. We regard their leaf-like shapes, cryptic colors, and escape movements as a convergence in defensive responses to visually hunting aquatic vertebrates, most likely diurnal predaceous fishes.

  4. The Nissan LEAF electric powertrain

    Energy Technology Data Exchange (ETDEWEB)

    Nakazawa, Shinsuke [Nissan Motor Co., Ltd. (Japan)

    2011-07-01

    The need for CO{sub 2} reduction as a countermeasure to global warming, and to move away from our dependence on fossil fuels as a countermeasure to energy security are urgent issues. One of the ultimate goals to achieving these targets is to develop a 'Zero emission car&apos; such as an electric vehicle or a fuel cell vehicle, along with the manufacturing of clean energy. Nissan have developed a new powertrain for the electric vehicle, and have installed it in the Nissan LEAF. Sales of the Nissan LEAF started in North America, Europe and Japan in 2010, with plans to sell it globally by 2012. In order to achieve an improved driving range, power performance and drivability performance, Nissan have adapted a high efficiency synchronous motor, a water-cooled inverter, and reducer. Moreover, the Nissan LEAF has the capability of a 3.3kW AC charge and a 50kW DC quick charge. This presentation will introduce the features of the electric powertrain adopted for Nissan LEAF. (orig.)

  5. Analysis of the influence of the Colatina Belt in the Campos and Espirito Santo Basins-Brazil; Analise da influencia da Faixa Colatina nas Bacias de Campos e Espirito Santo

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Gustavo Henrique Teixeira da; Simoes, Luiz Sergio Amarante; Souza, Iata Anderson de [Universidade Estadual Paulista (UNESP), Rio Claro, SP (Brazil). Inst. de Geociencias e Ciencias Exatas

    2008-07-01

    Recent discoveries in the Espirito Santo Basin confirm the importance of it in the national exploratory scenery (oil and gas production). The new fields like Carapo and Camarupim, beyond others, next to already known Golfinho and Canapu, totalize an addition of 560 million barrels. In this way, studies in the area add importance, as the case of the present research, where if it looked to analyze the influence of Colatina Belt in Espirito Santo Basin and secondarily in Campos Basin. The results had been gotten through the integration of diverse data, such as lineaments extracted from images SRTM, potential maps and analyze of seismic lines. It was concluded that the Colatina Belt if projects for the interior of the basins, but that the same one seems to be dislocated in relation to the direct projection of the continental features, being that its influence can be felt with bigger emphasis in the Campos Basin, while in the Espirito Santo it look like to have low importance with regard to the exploration aspects. Also it was verified the presence of numerous halo kinetic structures that affect all the mapped horizons, this element determine great importance in the generation of structural traps. (author)

  6. Evolutionary history of Otophysi (Teleostei, a major clade of the modern freshwater fishes: Pangaean origin and Mesozoic radiation

    Directory of Open Access Journals (Sweden)

    Saitoh Kenji

    2011-06-01

    Full Text Available Abstract Background Freshwater harbors approximately 12,000 fish species accounting for 43% of the diversity of all modern fish. A single ancestral lineage evolved into about two-thirds of this enormous biodiversity (≈ 7900 spp. and is currently distributed throughout the world's continents except Antarctica. Despite such remarkable species diversity and ubiquity, the evolutionary history of this major freshwater fish clade, Otophysi, remains largely unexplored. To gain insight into the history of otophysan diversification, we constructed a timetree based on whole mitogenome sequences across 110 species representing 55 of the 64 families. Results Partitioned maximum likelihood analysis based on unambiguously aligned sequences (9923 bp confidently recovered the monophyly of Otophysi and the two constituent subgroups (Cypriniformes and Characiphysi. The latter clade comprised three orders (Gymnotiformes, Characiformes, Siluriformes, and Gymnotiformes was sister to the latter two groups. One of the two suborders in Characiformes (Characoidei was more closely related to Siluriformes than to its own suborder (Citharinoidei, rendering the characiforms paraphyletic. Although this novel relationship did not receive strong statistical support, it was supported by analyzing independent nuclear markers. A relaxed molecular clock Bayesian analysis of the divergence times and reconstruction of ancestral habitats on the timetree suggest a Pangaean origin and Mesozoic radiation of otophysans. Conclusions The present timetree demonstrates that survival of the ancestral lineages through the two consecutive mass extinctions on Pangaea, and subsequent radiations during the Jurassic through early Cretaceous shaped the modern familial diversity of otophysans. This evolutionary scenario is consistent with recent arguments based on biogeographic inferences and molecular divergence time estimates. No fossil otophysan, however, has been recorded before the Albian, the

  7. Evolutionary history of Otophysi (Teleostei), a major clade of the modern freshwater fishes: Pangaean origin and Mesozoic radiation.

    Science.gov (United States)

    Nakatani, Masanori; Miya, Masaki; Mabuchi, Kohji; Saitoh, Kenji; Nishida, Mutsumi

    2011-06-22

    Freshwater harbors approximately 12,000 fish species accounting for 43% of the diversity of all modern fish. A single ancestral lineage evolved into about two-thirds of this enormous biodiversity (≈ 7900 spp.) and is currently distributed throughout the world's continents except Antarctica. Despite such remarkable species diversity and ubiquity, the evolutionary history of this major freshwater fish clade, Otophysi, remains largely unexplored. To gain insight into the history of otophysan diversification, we constructed a timetree based on whole mitogenome sequences across 110 species representing 55 of the 64 families. Partitioned maximum likelihood analysis based on unambiguously aligned sequences (9923 bp) confidently recovered the monophyly of Otophysi and the two constituent subgroups (Cypriniformes and Characiphysi). The latter clade comprised three orders (Gymnotiformes, Characiformes, Siluriformes), and Gymnotiformes was sister to the latter two groups. One of the two suborders in Characiformes (Characoidei) was more closely related to Siluriformes than to its own suborder (Citharinoidei), rendering the characiforms paraphyletic. Although this novel relationship did not receive strong statistical support, it was supported by analyzing independent nuclear markers. A relaxed molecular clock Bayesian analysis of the divergence times and reconstruction of ancestral habitats on the timetree suggest a Pangaean origin and Mesozoic radiation of otophysans. The present timetree demonstrates that survival of the ancestral lineages through the two consecutive mass extinctions on Pangaea, and subsequent radiations during the Jurassic through early Cretaceous shaped the modern familial diversity of otophysans. This evolutionary scenario is consistent with recent arguments based on biogeographic inferences and molecular divergence time estimates. No fossil otophysan, however, has been recorded before the Albian, the early Cretaceous 100-112 Ma, creating an over 100

  8. Fish associated with aquatic macrophytes in the Chacororé-Sinhá Mariana Lake system and Mutum River, Pantanal of Mato Grosso, Brazil Peixes associados a macrófitas aquáticas no sistema de baías Chacororé-Sinhá Mariana e rio Mutum, Pantanal - MT

    Directory of Open Access Journals (Sweden)

    EB. Pacheco

    2009-02-01

    Full Text Available On the left bank of the Cuibá River, one of the main tributaries of the Pantanal in Mato Grosso, are located the Chacororé and Sinhá Mariana Lakes and the Mutum River, the littoral regions of which are covered with aquatic macrophytes, dominated by the species Eichhornia crassipes and Eichhornia azurea. To examine the ichthyofauna associated with this vegetation, in the year 2003, 3510 fish were collected, distributed among 83 species, and the limnological variables verified near the macrophyte stands where they were sampled. The most abundant and richest order was the Characiformes, followed by the Gymnotiformes and Siluriformes. Analysis of similarity showed a very low, or null, index that the limnological conditions and morphology of the aquatic macrophyte species provide habitat sufficiently homogeneous to give. The limnological conditions and morphology of the aquatic macrophyte species provide a sufficient habitat heterogeneity to give very low, or null, index values. Thus, environmental conservation measures should be more effective in promoting the conservation of the species, given the high levels of biological diversity found in the habitats studied.À margem esquerda do rio Cuiabá, um dos principais afluentes do Pantanal matogrossense, estão localizadas as baías Chacororé e Sinhá Mariana e o rio Mutum, cujas regiões litorâneas são cobertas por macrófitas aquáticas. Com o intuito de se verificar a ictiofauna associada a esta vegetação, no ano de 2003, foram coletados 3510 peixes distribuídos em 83 espécies e verificados os valores das variáveis limnológicas próximo aos bancos de macrófitas onde estes foram amostrados. A ordem mais abundante e de maior riqueza foi Characiformes, seguida por Gymnotiformes e Siluriformes. As condições limnológicas e a morfologia das espécies de macrófitas proporcionam heterogeneidade de hábitat suficiente para obtenção de valores dos índices de similaridade baixos ou mesmo

  9. The fish fauna in tropical rivers: The case of the Sorocaba river basin, SP, Brazil

    Directory of Open Access Journals (Sweden)

    Welber Senteio Smith

    2003-09-01

    Full Text Available A survey was carried out on the fish species in the Sorocaba River basin, the main tributary of the left margin of the Tietê River, located in the State of São Paulo, Brazil. The species were collected with gill nets. After identification of the specimens, their relative abundance, weight and standard length were determined. Up to the present moment there are not any studies that focus this subject in this hydrographic basin. Fifty-three species, distributed in eighteen families and six orders were collected. Characiformes were represented by twenty-eight species, Siluriformes by seventeen species, the Gymnotiformes by three species, Perciformes and Cyprinodontiformes by two species, and the Synbranchiformes by one species. Among the collected species there were two exotic. The most abundant species were Astyanax fasciatus and Hypostomus ancistroides. In relation to total weight the most representative species were Hoplias malabaricus and Hypostomus ancistroides. Cyprinus carpio, Prochilodus lineatus, Schizodon nasutus and Hoplias malabaricus were the most representative species in relation to average weight. Largest standard length were recorded for Sternopygus macrurus, Steindachnerina insculpta, Eigenmannia aff. virescens and Cyprinus carpioSe realizó un análisis de las especies de peces de la cuenca del Río Sorocaba, el principal tributario de la margen izquierda del Río Tietê, localizado en el estado de Sao Paulo, Brasil. Las especies fueron recolectadas con redes agalleras. Luego de la identificación de los especímenes, fue determinada su abundancia relativa, peso, y longitud estandar. Hasta el presente, no hay ningún otro estudio que analice estos aspectos en dicha cuenca hidrográfica. Fueron recolectados 55 especies, distribuidas en 18 familias y 6 ordenes. Los Characiformes estuvieron representados por 28 especies, Siluriformes por 17 especies, Gymnotiformes por 3 especies, Perciformes y Cyprinodontiformes por 2 especies, y

  10. Influência da estrutura do hábitat sobre a ictiofauna de um riacho em uma micro-bacia de pastagem, São Paulo, Brasil Habitat structure and stream fishes in a pasture basin, São Paulo, Brazil

    Directory of Open Access Journals (Sweden)

    Cristiane de P. Ferreira

    2006-09-01

    Full Text Available Este trabalho foi desenvolvido em quatro trechos de um riacho em área de pastagem no noroeste do Estado de São Paulo, com o objetivo de examinar a composição e estrutura quantitativa da ictiofauna e investigar sua relação com as características do hábitat. Os peixes foram coletados nos três meses centrais dos períodos seco e chuvoso por meio de uma passagem de pesca elétrica por mês. A análise da qualidade química da água mostrou condições boas nos quatro trechos, enquanto que a análise da integridade física do hábitat mostrou condições pobres para os trechos 2 e 3 e regulares para os trechos 1 e 4. Foram coletadas 27 espécies de peixes, totalizando 1.241 indivíduos e 5,1 kg. A estrutura quantitativa da ictiofauna demonstrou maior associação com a estrutura do hábitat do que com a sazonalidade visto que os trechos 1 e 2 foram agrupados separadamente dos trechos 3 e 4, independentemente do período de amostragem. De acordo com a análise de correspondência canônica, a elevada abundância de Gymnotus carapo Linnaeus, 1758 nos trechos 1 e 2 esteve associada principalmente com a abundância de vegetação marginal. O maior volume de hábitat no trecho 3 explicou a abundância de Piabina argentea Reinhardt, 1867, e a predominância de substratos rochosos no trecho 4 explicaram a abundância de Hypostomus nigromaculatus (Schubart, 1964.Four stream stretches (sites 1-4 in a pasture area of the northwestern São Paulo state were studied, aiming to examine the composition and quantitative structure of the ichthyofauna and investigate its relation with habitat features. Fishes were collected during the three most representative months of the dry and wet periods by one electrofishing pass in each month. Chemical water quality analysis showed good conditions in all sites, whereas physical habitat integrity analysis showed poor conditions to the sites 2 and 3 and fair to the sites 1 and 4. Twenty seven fish species were collected

  11. The sustainable car company - or the comeback of the electric car

    Energy Technology Data Exchange (ETDEWEB)

    Sticher, Georg; Rizoulis, Dimitrios [The Boston Consulting Group, Muenchen (Germany)

    2008-07-01

    Every day there are article published about the future of propulsion technology. Opinions are diverging: 'We'll sell nothing but hybrids by 2020' says one automotive executive; whereas for another power train executive ''Hybrids are a violation of physics'. The topic has moved beyond specialized automotive magazines and is strongly emotionalized: Hollywood stars appear driving hybrid vehicles and a documentary film charges the automotive industry as guilty for conspiring against and 'killing the electric car&apos;. Those emotional discussions are largely driven by the announcement of many new vehicles powered by hybrid-electric power trains, fuel cells or batteries. The public is overwhelmed by announcements and can hardly tell concept vehicles from production announcements apart. One core aspect of sustainability is the reduction of CO2 emissions and the increase of vehicle efficiency. The electrification of the vehicle will have to be an integral part of every OEMs and suppliers' portfolio. But without adequate incentives of consumers to purchase the cars and of utilities and/or private investors to provide the necessary infrastructure, the emergence of the electric vehicle may be off to another false start. We do want to offer a structured, multi-stakeholder view in an attempt to de-mystify this rather complex topic. To this, we will present facts on what drives the need for change in the propulsion systems market, what are the viable technological options, what market scenario is likely for 2020 and what does this entail for the major stakeholders. (orig.)

  12. Electric organ discharges and electric images during electrolocation

    Science.gov (United States)

    Assad, C.; Rasnow, B.; Stoddard, P. K.

    1999-01-01

    Weakly electric fish use active electrolocation - the generation and detection of electric currents - to explore their surroundings. Although electrosensory systems include some of the most extensively understood circuits in the vertebrate central nervous system, relatively little is known quantitatively about how fish electrolocate objects. We believe a prerequisite to understanding electrolocation and its underlying neural substrates is to quantify and visualize the peripheral electrosensory information measured by the electroreceptors. We have therefore focused on reconstructing both the electric organ discharges (EODs) and the electric images resulting from nearby objects and the fish's exploratory behaviors. Here, we review results from a combination of techniques, including field measurements, numerical and semi-analytical simulations, and video imaging of behaviors. EOD maps are presented and interpreted for six gymnotiform species. They reveal diverse electric field patterns that have significant implications for both the electrosensory and electromotor systems. Our simulations generated predictions of the electric images from nearby objects as well as sequences of electric images during exploratory behaviors. These methods are leading to the identification of image features and computational algorithms that could reliably encode electrosensory information and may help guide electrophysiological experiments exploring the neural basis of electrolocation.

  13. Why the short face? Developmental disintegration of the neurocranium drives convergent evolution in neotropical electric fishes.

    Science.gov (United States)

    Evans, Kory M; Waltz, Brandon; Tagliacollo, Victor; Chakrabarty, Prosanta; Albert, James S

    2017-03-01

    Convergent evolution is widely viewed as strong evidence for the influence of natural selection on the origin of phenotypic design. However, the emerging evo-devo synthesis has highlighted other processes that may bias and direct phenotypic evolution in the presence of environmental and genetic variation. Developmental biases on the production of phenotypic variation may channel the evolution of convergent forms by limiting the range of phenotypes produced during ontogeny. Here, we study the evolution and convergence of brachycephalic and dolichocephalic skull shapes among 133 species of Neotropical electric fishes (Gymnotiformes: Teleostei) and identify potential developmental biases on phenotypic evolution. We plot the ontogenetic trajectories of neurocranial phenotypes in 17 species and document developmental modularity between the face and braincase regions of the skull. We recover a significant relationship between developmental covariation and relative skull length and a significant relationship between developmental covariation and ontogenetic disparity. We demonstrate that modularity and integration bias the production of phenotypes along the brachycephalic and dolichocephalic skull axis and contribute to multiple, independent evolutionary transformations to highly brachycephalic and dolichocephalic skull morphologies.

  14. Fish associated with aquatic macrophytes in the Chacororé-Sinhá Mariana Lake system and Mutum River, Pantanal of Mato Grosso, Brazil.

    Science.gov (United States)

    Pacheco, E B; Da-Silva, C J

    2009-02-01

    On the left bank of the Cuibá River, one of the main tributaries of the Pantanal in Mato Grosso, are located the Chacororé and Sinhá Mariana Lakes and the Mutum River, the littoral regions of which are covered with aquatic macrophytes, dominated by the species Eichhornia crassipes and Eichhornia azurea. To examine the ichthyofauna associated with this vegetation, in the year 2003, 3510 fish were collected, distributed among 83 species, and the limnological variables verified near the macrophyte stands where they were sampled. The most abundant and richest order was the Characiformes, followed by the Gymnotiformes and Siluriformes. Analysis of similarity showed a very low, or null, index that the limnological conditions and morphology of the aquatic macrophyte species provide habitat sufficiently homogeneous to give. The limnological conditions and morphology of the aquatic macrophyte species provide a sufficient habitat heterogeneity to give very low, or null, index values. Thus, environmental conservation measures should be more effective in promoting the conservation of the species, given the high levels of biological diversity found in the habitats studied.

  15. Energetic cost of communication.

    Science.gov (United States)

    Stoddard, Philip K; Salazar, Vielka L

    2011-01-15

    Communication signals may be energetically expensive or inexpensive to produce, depending on the function of the signal and the competitive nature of the communication system. Males of sexually selected species may produce high-energy advertisement signals, both to enhance detectability and to signal their size and body condition. Accordingly, the proportion of the energy budget allocated to signal production ranges from almost nothing for many signals to somewhere in excess of 50% for acoustic signals in short-lived sexually selected species. Recent data from gymnotiform electric fish reveal mechanisms that regulate energy allocated to sexual advertisement signals through dynamical remodeling of the excitable membranes in the electric organ. Further, males of the short-lived sexually selected species, Brachyhypopomus gauderio, trade off among different metabolic compartments, allocating energy to signal production while reducing energy used in other metabolic functions. Female B. gauderio, by contrast, do not trade off energy between signaling and other functions. To fuel energetically expensive signal production, we expect a continuum of strategies to be adopted by animals of different life history strategies. Future studies should explore the relation between life history and energy allocation trade-offs.

  16. Composición de especies y diversidad de peces en tres cuerpos de agua en la cuenca alta del río Itaya

    Directory of Open Access Journals (Sweden)

    Javier del Águila Chávez

    2013-06-01

    Full Text Available En el presente trabajo se describe sobre la diversidad en tres cuerpos de agua de la cuenca alta del río Itaya, concesión de conservación de la universidad científica del Perú, en una evaluación rápida en los meses de junio y julio del 2012. Se colectaron datos y muestras de peces en Lamas cocha (LC, cocha Anguilla (CA y Tipishca Luz de Oriente (TLO. Los peces fueron colectados utilizando una batería de redes de diferentes medidas 1.5, 2, 2.5, 3, 3.5 y 4 pulgadas de de abertura de malla. Se reportan 17 familias taxonómicas, de las cuales 9 familias pertenecen al orden Characiformes (53%, 3 familias pertenecen al orden de los Siluriformes (17%, 2 familias pertenecen al orden de los Gymnotiformes (12% y al orden Perciformes (12% y una familia pertenece al orden Beloniformes (6%. La predominancia de las familias taxonómicas en los tres ambientes fueron Characidae, Curimatidae, Acestrorhynchidae (Characiformes y Cichlidae (Perciformes. Sin embargo, la ocurrencia de exclusividad de una determinada familia fue observada en los tres cuerpos de aguas; tenemos de esta forma la familia Hemiodontidae solo tienen ocurrencia en Lamas cocha, la ocurrencia de la familia Prochilodontidae (Characiformes y Callichthyidae (Siluriformes en Cocha Anguillal y finalmente la ocurrencia de las familias Pimelodidae (Siluriformes, Sciaenidae (Perciformes y Belonidae (Beloniformes en la Tipishca Luz de Oriente.

  17. Composición de especies y diversidad de peces en tres cuerpos de agua en la cuenca alta del río Itaya

    Directory of Open Access Journals (Sweden)

    Javier del Águila Chávez

    2013-06-01

    Full Text Available En el presente trabajo se describe sobre la diversidad en tres cuerpos de agua de la cuenca alta del río Itaya, concesión de conservación de la universidad científica del Perú, en una evaluación  rápida en los meses de junio y julio del 2012. Se colectaron datos y muestras de peces en Lamas cocha (LC, cocha Anguilla (CA y Tipishca Luz de Oriente (TLO. Los peces fueron colectados utilizando una batería de redes de diferentes medidas 1.5, 2, 2.5, 3, 3.5 y 4 pulgadas de de abertura de malla. Se reportan 17 familias taxonómicas, de las cuales 9 familias pertenecen al orden Characiformes (53%, 3 familias pertenecen al orden de los Siluriformes (17%, 2 familias pertenecen al orden de los Gymnotiformes (12%  y al orden Perciformes (12% y una familia pertenece al orden Beloniformes (6%. La predominancia de las familias taxonómicas en los tres ambientes fueron Characidae, Curimatidae, Acestrorhynchidae (Characiformes y Cichlidae (Perciformes. Sin embargo, la ocurrencia de exclusividad de una determinada familia fue observada en los tres cuerpos de aguas; tenemos de esta forma la familia Hemiodontidae solo tienen ocurrencia en Lamas cocha, la ocurrencia de la familia Prochilodontidae (Characiformes y Callichthyidae (Siluriformes en Cocha Anguillal y finalmente la ocurrencia de las familias Pimelodidae (Siluriformes, Sciaenidae (Perciformes y Belonidae (Beloniformes en la Tipishca Luz de Oriente.

  18. Active sensing associated with spatial learning reveals memory-based attention in an electric fish.

    Science.gov (United States)

    Jun, James J; Longtin, André; Maler, Leonard

    2016-05-01

    Active sensing behaviors reveal what an animal is attending to and how it changes with learning. Gymnotus sp, a gymnotiform weakly electric fish, generates an electric organ discharge (EOD) as discrete pulses to actively sense its surroundings. We monitored freely behaving gymnotid fish in a large dark "maze" and extracted their trajectories and EOD pulse pattern and rate while they learned to find food with electrically detectable landmarks as cues. After training, they more rapidly found food using shorter, more stereotyped trajectories and spent more time near the food location. We observed three forms of active sensing: sustained high EOD rates per unit distance (sampling density), transient large increases in EOD rate (E-scans) and stereotyped scanning movements (B-scans) were initially strong at landmarks and food, but, after learning, intensified only at the food location. During probe (no food) trials, after learning, the fish's search area and intense active sampling was still centered on the missing food location, but now also increased near landmarks. We hypothesize that active sensing is a behavioral manifestation of attention and essential for spatial learning; the fish use spatial memory of landmarks and path integration to reach the expected food location and confine their attention to this region. Copyright © 2016 the American Physiological Society.

  19. Separability of drag and thrust in undulatory animals and machines

    Science.gov (United States)

    Bale, Rahul; Shirgaonkar, Anup A.; Neveln, Izaak D.; Bhalla, Amneet Pal Singh; Maciver, Malcolm A.; Patankar, Neelesh A.

    2014-12-01

    For nearly a century, researchers have tried to understand the swimming of aquatic animals in terms of a balance between the forward thrust from swimming movements and drag on the body. Prior approaches have failed to provide a separation of these two forces for undulatory swimmers such as lamprey and eels, where most parts of the body are simultaneously generating drag and thrust. We nonetheless show that this separation is possible, and delineate its fundamental basis in undulatory swimmers. Our approach unifies a vast diversity of undulatory aquatic animals (anguilliform, sub-carangiform, gymnotiform, bal-istiform, rajiform) and provides design principles for highly agile bioinspired underwater vehicles. This approach has practical utility within biology as well as engineering. It is a predictive tool for use in understanding the role of the mechanics of movement in the evolutionary emergence of morphological features relating to locomotion. For example, we demonstrate that the drag-thrust separation framework helps to predict the observed height of the ribbon fin of electric knifefish, a diverse group of neotropical fish which are an important model system in sensory neurobiology. We also show how drag-thrust separation leads to models that can predict the swimming velocity of an organism or a robotic vehicle.

  20. Fish community structure of Juramento reservoir, São Francisco River basin, Minas Gerais, Brazil Estrutura da comunidade de peixes do reservatório de Juramento, bacia do Rio São Francisco, Minas Gerais, Brasil

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    André R. M. Silva

    2006-09-01

    Full Text Available Many rivers in Brazil as the São Francisco (SFR have been impounded for reservoirs construction purposes. However, there is a lack of knowledge on their fish fauna in many areas, including headwaters. The present study aimed to describe the fish community structure from Juramento reservoir, located on Juramento River, a branch of SFR basin. Six bimonthly samplings were made in four different sites. Gill and cast nets, beach seines and sieves were used to collect fish. Ecological indexes as well as the relationship between fish abundance and some limnological variables were determined. 3288 fish belonging to 33 species (16.5% of the total described for SFR basin were captured, being 75.7% Characiformes, 18.1% Siluriformes, 3% Cyprinodontiformes and 3% Gymnotiformes. Only two non-native species, 'tamboatá' - Hoplosternum littorale (Hancock, 1828 and 'trairão' - Hoplias lacerdae Ribeiro, 1908 were found. The highest catches in number occurred in the dry period (March-October and the lowest one in the wet season (November-February. Diversity was higher at Barragem station and richness did not vary between reservoir zones. Five migratory species were found downstream of the dam (four exclusively there, whereas only the 'curimbatá-pioa' - Prochilodus costatus Valenciennes, 1850 occurred in the reservoir. The low observed correlations between fish abundance and the limnological variables utilized suggest that the local fish fauna is not strongly affected by their variation.No Brasil, vários rios, como os da bacia do São Francisco (RSF, são barrados para a formação de reservatórios. Entretanto, o estudo desta ictiofauna, especialmente a dos rios de cabeceira, ainda deixa a desejar. O presente estudo descreveu a estrutura da ictiofauna do reservatório de Juramento, Rio Juramento, bacia do RSF. Foram realizadas seis coletas bimestrais em quatro locais empregando-se redes de emalhar, tarrafas, arrastões e peneiras. Foram determinados

  1. Dynamics and stimulus-dependence of pacemaker control during behavioral modulations in the weakly electric fish, Apteronotus.

    Science.gov (United States)

    Dye, J

    1987-08-01

    1. Weakly electric fish generate around their bodies low-amplitude, AC electric fields which are used both for the detection of objects and intraspecific communication. The types of modulation in this signal of which the high-frequency wave-type gymnotiform, Apteronotus, is capable are relatively few and stereotyped. Chief among these is the chirp, a signal used in courtship and agonistic displays. Chirps are brief and rapid accelerations in the normally highly regular electric organ discharge (EOD) frequency. 2. Chirping can be elicited artificially in these animals by the use of a stimulus regime identical to that typically used to elicit another behavior, the jamming avoidance response (JAR). The neuronal basis for the JAR, a much slower and lesser alteration in EOD frequency, is well understood. Examination of the stimulus features which induce chirping show that, like the JAR, there is a region of frequency differences between the fish's EOD and the interfering signal that maximally elicits the response. Moreover, the response is sex-specific with regard to the sign of the frequency difference, with females chirping preferentially on the positive and most males on the negative Df. These features imply that the sensory mechanisms involved in the triggering of these communicatory behaviors are fundamentally similar to those explicated for the JAR. 3. Additionally, two other modulatory behaviors of unknown significance are described. The first is a non-selective rise in EOD frequency associated with a JAR stimulus, occurring regardless of the sign of the Df. This modulation shares many characteristics with the JAR. The second behavior, which we have termed a 'yodel', is distinct from and kinetically intermediate to chirping and the JAR. Moreover, unlike the other studied electromotor behaviors it is generally produced only after the termination of the eliciting stimulus.

  2. Utilization of the fish ladder at the Engenheiro Sergio Motta Dam, Brazil, by long distance migrating potamodromous species

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    Sérgio Makrakis

    Full Text Available Utilization of the fish ladder installed at the Engenheiro Sergio Motta Dam (also known as Porto Primavera on the Paraná River, Southern Brazil, by long-distance migrating potamodromous species (sampling Protocol I, and ascending and descending movements (Protocol II were evaluated. Three pools along the fish ladder (designated as lower, middle, and upper were sampled monthly between December, 2004 and March, 2005 to determine the abundance of species in the ladder. The ascending and descending movements of the species in the ladder were also analyzed in the same period. In the samples for both protocols, 37 species representing 17 families and 5 orders (Characiformes, Siluriformes, Perciformes, Gymnotiformes, and Myliobatiformes were recorded. Characiformes were represented by 21 species. Long- distance migratory species (11 species predominated in the ladder (60% of the total number of individuals, with high abundance of Rhinelepis aspera (5645 individuals. For protocol I, mean abundance varied greatly among the months and pools, with lowest values in December and March for all pools, and highest in January for the lower pool due to high capture of R. aspera. Fish abundance declined from the lower to the upper pool, especially for R. aspera and Rhaphiodon vulpinus. For Protocol II, 17 species were recorded ascending the ladder, where Astyanax altiparanae and Leporinus friderici were the most abundant species (684 and 111 individuals, respectively. However, 18 species showed descending movements, with high captures of Metynnis maculatus and A. altiparanae (339 and 319 individuals, respectively. Twelve species (52% moved in both directions, and among the seven migratory species sampled, four were recorded ascending and descending, and three species only ascending the ladder. The fish ladder appears to selectively favor species with high swimming capabilities. A discussion is presented on the requirements for future research on attraction to the

  3. Molecular evolution of ependymin and the phylogenetic resolution of early divergences among euteleost fishes.

    Science.gov (United States)

    Ortí, G; Meyer, A

    1996-04-01

    The rate and pattern of DNA evolution of ependymin, a single-copy gene coding for a highly expressed glycoprotein in the brain matrix of teleost fishes, is characterized and its phylogenetic utility for fish systematics is assessed. DNA sequences were determined from catfish, electric fish, and characiforms and compared with published ependymin sequences from cyprinids, salmon, pike, and herring. Among these groups, ependymin amino acid sequences were highly divergent (up to 60% sequence difference), but had surprisingly similar hydropathy profiles and invariant glycosylation sites, suggesting that functional properties of the proteins are conserved. Comparison of base composition at third codon positions and introns revealed AT-rich introns and GC-rich third codon positions, suggesting that the biased codon usage observed might not be due to mutational bias. Phylogenetic information content of third codon positions was surprisingly high and sufficient to recover the most basal nodes of the tree, in spite of the observation that pairwise distances (at third codon positions) were well above the presumed saturation level. This finding can be explained by the high proportion of phylogenetically informative nonsynonymous changes at third codon positions among these highly divergent proteins. Ependymin DNA sequences have established the first molecular evidence for the monophyly of a group containing salmonids and esociforms. In addition, ependymin suggests a sister group relationship of electric fish (Gymnotiformes) and Characiformes, constituting a significant departure from currently accepted classifications. However, relationships among characiform lineages were not completely resolved by ependymin sequences in spite of seemingly appropriate levels of variation among taxa and considerably low levels of homoplasy in the data (consistency index = 0.7). If the diversification of Characiformes took place in an "explosive" manner, over a relatively short period of time

  4. Stability and spatio-temporal structure in fish assemblages of two floodplain lagoons of the lower Orinoco River

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    Nirson González

    Full Text Available Fish assemblage structure and variability were analyzed in two floodplain lagoons (Las Arhuacas and Los Cardonales along the lower Orinoco over a hydrological cycle. Every three months during continuous three-day sampling, experimental gill nets (5 to 12.5 cm of mesh opening and 1 mm-mesh seine nets were utilized according to the types of habitats presents. A total of 133 fish species were found in Las Arhuacas and 95 species in Cardonales. Fifty five and 17 species were exclusive to Las Arhuacas and Los Cardonales respectively, and 77 were common to both lagoons. In Las Arhuacas, the most speciesrich orders were Characiformes, Siluriformes, Perciformes and Gymnotiformes and in Los Cardonales, the most species-rich orders were Characiformes, Siluriformes, Clupeiformes and Perciformes. The richness, abundance and biomass were significantly higher (p < 0.001 in Arhuacas than in Cardonales. In general, the fishes assemblage was highly variable during the high water phase and moderately stable during low water phase in both lagoons, with more stability or less variability in Cardonales than Arhuacas. Also, there were significant differences in the fish assemblages between the two lagoons, mainly during low waters (ANOSIM; p < 0.001. The species that contributed most to the mean dissimilarity between the lagoons were Hypostomus argus, Aphanotorulus ammophilus, Potamorhina altamazonica, Prochilodus mariae, Loricaria gr. cataphracta, Oxydoras sifontesi, Hydrolycus armatus, Hyphopthalmus edentatus and Pterodoras rivasi. The last four species were more commonly collected in Los Cardonales. Also, the species of small size (mainly SL < 5 cm such as Rhinosardinia amazonica, Moenkhausia sp. 1 "lepidura", Moenkhausia sp. 2, Aphyocharax alburnus, Characidium sp. 1, Moenkhausia sp. 3, Exodon paradoxus and Roeboides dientonito contributed to the mean dissimilarity among the beach and aquatic vegetation habitats. The patterns of the species assemblage

  5. Perfil Ictiofaunístico de duas Lagoas no Rio Paraná, Região do Parque Nacional de Ilha Grande - PR. = Ictiofaunistic profile of two Rio Paraná lagoons, Region of Ilha Grande National Park - PR.

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    Wladimir M. Domingues

    2008-07-01

    Full Text Available O Rio Paraná é o décimo maior do mundo em descarga e nele se encontra a região do Parque Nacional de Ilha Grande, que é formada por um conjunto de ilhas, lagoas e várzeas periodicamente alagadas, sendo estas de extrema importância para os peixes, servindo de refúgio contra predação, berçário natural e áreas de alimentação para muitas espécies de peixes. Este artigo apresenta um levantamento icitiofaunístico nas lagoas Saraiva e São João, situadas no Parque Nacional de Ilha Grande, com enfoque nas variações espaço-temporais, na composição específica e estrutura etária das assembléias de peixes, sendo que estes foram amostrados em coletas trimestrais, utilizando-se redes de espera de diferentes malhagens. Em termos de número de indivíduos capturados e proporção, tem-se 54% das espécies pertencentes a ordem Characiformes, 42% a Siruliformes, 3% a Perciformes. Rajiformes e Gymnotiformes contribuíram com menos de 1,5% do total das capturas. Na lagoa Saraiva foram capturadas 34 espécies pertencentes a cinco ordens e 17 famílias, destacando-se numericamente Loricariichthys platymetopon, Raphiodon vulpinus, Serrasalmus marginatus e Plagioscion squamosissimus. As maiores contribuições em peso foram proporcionadas por R. vulpinus, Potanotrygon motoro, P. squamosissimus e S. marginatus. Na lagoa São João ocorreram 46 espécies pertencentes a cinco ordens e 17 famílias, destacando-se em número L. platymetopon, Acestrohynchus lacustris, Serrasalmus spilopleura e S. marginatus. Em peso, Prochilodus lineatus, A. lacustris, L. platymetopon e Serrasalmus spilopleura foram as mais representativas. Destaca-se que a maioria das espécies registradas em ambas as lagoas são típicas de ambientes lênticos, utilizando esses locais para seu desenvolvimento e crescimento. = Paraná River is the tenth river in the world concerning to discharge and surrounding it Ilha Grande National Park region is localized, wich is formed by a