ABSTRACT
Gymnotus is the most studied genus of the order Gymnotiformes, but the morphological similarities of the different species make it difficult to identify taxa reliably. The present study is a continuation of the ongoing research into the taxonomic diversity of the stocks of Gymnotus sold as live bait in the Pantanal, Brazil. These studies have been based on cytogenetic analyses, DNA barcoding, and the analysis of coloration patterns. The results of the cytogenetic analysis confirmed the presence of three distinct strains, recognized as Gymnotus paraguensis, G. sylvius, and G. pantanal. However, the results revealed that the molecular operational taxonomic units identified as G. paraguensis actually include a relatively diverse set of fish, separated by considerable genetic distances. As the G. paraguensis specimens also presented considerable variation in coloration patterns, further genetic diversity analyses were conducted on these individuals, to test the hypothesis that more than one species is present in this cytotaxonomic unit. The haplotype network revealed a regional pattern in the distribution of this species. The results indicate that the observed variation in coloration patterns is associated with a high degree of phenotypic plasticity in G. paraguensis. These findings emphasize the importance of using an integrative approach for a more accurate diagnosis of Gymnotus, in particular, the species marketed as live bait for the fisheries of the upper Paraguay River basin in the Brazilian Pantanal.
Subject(s)
Gymnotiformes , Adaptation, Physiological , Animals , Brazil , Ecosystem , Gymnotiformes/geneticsABSTRACT
The capture of live bait for sport fishing is an important activity for fishing communities. The main species used for this purpose are members of the genus Gymnotus, which comprises numerous species of cryptic nature that are difficult to identify based on external morphology. The aims of this work were to identify through partial sequences of the COI gene Gymnotus species fished in the Jacaré-Guaçu River, SP, and to develop a molecular diagnostic approach using PCR-RFLP to identify these species. Partial COI sequences were compared to those of other species deposited in GenBank. The sequences were assessed in the NEBCutter program to determine restriction sites in the sequence and the enzymes to be tested. Phenetic analysis performed by Neighbor-Joining method showed that the specimens sampled belong to two species preliminary identified here as G. cf. sylvius and G. cf. cuia, with G. cf. sylvius accounting for 95.2% of the individuals sampled. The enzymes NlaIII and SacI generated fragments that allowed distinguishing the Gymnotus species using PCR-RFLP. This analysis can be used to accurately identify these species, which is fundamental for monitoring Gymnotus fishing and assessing the conservation of this genetic resource.(AU)
A captura de iscas-vivas para a pesca esportiva constitui uma atividade importante em comunidades de pescadores. As principais espécies utilizadas para este propósito pertencem ao gênero Gymnotus, o qual compreende inúmeras espécies de natureza críptica que dificulta a identificação baseada na morfologia externa. Os objetivos deste trabalho foram identificar através de sequências parciais do gene COI, espécies de Gymnotus capturadas no Rio Jacaré-Guaçu, Ibitinga, SP, e desenvolver um diagnóstico molecular por meio de PCR-RFLP. Sequências parciais de COI foram comparadas com outras espécies depositadas no GenBank. As sequências foram analisadas no Programa NebCutter para determinar os sítios de restrição e definir as enzimas a serem testadas. A análise fenética pelo método de Neighbor-Joining mostrou que os espécimes pertencem a duas espécies identificadas preliminarmente aqui como G. cf. sylvius e G. cf. cuia, sendo que G. cf. sylvius representou 95,2% dos indivíduos amostrados. As enzimas NlaIII e SacI geraram fragmentos que permitiram discriminar as espécies por meio de PCR-RFLP. Esta análise pode ser usada na identificação precisa destas espécies, fundamental na proposição de monitoramento da pesca de Gymnotus na região e para medidas adequadas de conservação.(AU)
Subject(s)
Animals , Polymorphism, Restriction Fragment Length , Gymnotiformes/classification , Gymnotiformes/geneticsABSTRACT
A new species of the Eigenmannia trilineata species group is described from the río Orinoco basin, Venezuela. The new species is distinguished from congeners by a unique set of characters including an ossified basibranchial 1; 198-217 anal-fin rays; suborbital depth, 21.3-26.1% HL; length of anterodorsal process of maxilla equal to the width of the posterior nostril; premaxilla with 17 teeth distributed in three rows; hyaline pectoral and anal fins; and number of scale series above lateral line, 9-10. It raises the number of species allocated to the Eigenmannia trilineata species group to 13 and the number of species within the genus to 18.(AU)
Se describe una nueva especie del grupo Eigenmannia trilineata de la cuenca del río Orinoco, Venezuela. La nueva especie se distingue de sus congéneres por una combinación única de caracteres, incluyendo el basibranquial 1 osificado; número de radios de la anal, 198-217; profundidad del suborbital, 21.3-26.1% HL; longitud del proceso anterodorsal de la maxila igual al ancho de la narina posterior; 17 dientes premaxilares distribuidos en tres hileras; aletas pectoral y anal hialinas; y 9-10 hileras de escamas sobre la serie de la línea lateral. La presente contribución eleva el número de especies del grupo Eigenmannia trilineata a 13, y a 18 aquellas dentro del género.(AU)
