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Three New Species of the Neotropical Electric Fish Rhabdolichops (Gymnotiformes: Sternopygidae) from the Central Amazon, with a New Diagnosis of the Genus

Three new species of the Neotropical electric fish Rhabdolichops are described from the lowland Central Amazon Basin of Brazil. These taxa are described using features of color pattern, morphometric and meristic traits, squamation, and osteology. Rhabdolichops nigrimans and R. navalha are known only...

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Bibliographic Details
Published in:Copeia 2006-03, Vol.2006 (1), p.27-42
Main Authors: Correa, S B, Crampton, W G, Albert, J S
Format: Article
Language:English
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Summary:Three new species of the Neotropical electric fish Rhabdolichops are described from the lowland Central Amazon Basin of Brazil. These taxa are described using features of color pattern, morphometric and meristic traits, squamation, and osteology. Rhabdolichops nigrimans and R. navalha are known only from low-conductivity blackwater systems whereas R. lundbergi occurs almost exclusively in the main channel of high-conductivity whitewater rivers and adjacent floodplain channels. Rhabdolichops nigrimans and R. lundbergi are sister species, forming a sister clade to all other Rhabdolichops species, and retaining transitional phenotypes between the genera Eigenmannia and Rhabdolichops. Rhabdolichops nigrimans, but not R. lundbergi, displays a striking sexual dimorphism in caudal appendage length. Rhabdolichops navalha and R. stewarti are sister species nested within a clade comprising R. eastwardi and R. caviceps + R. troscheli. Rhabdolichops navalha exhibits a unique morphology of the electric organ where the posterior margin ends abruptly and is replaced posteriorly by rigid and transparent non-electrogenic tissue.Tres especies novas de peixes eletricos neotropicais, Rhabdolichops, sao descritas da bacia Amazonica, Brasil. Estas especies sao descritas com base em caracteristicas de pigmentacao, morfologia, osteologia e dados meristicos. Rhabdolichops nigrimans e R. navalha sao conhecidos exclusivamente de sistemas de aguas pretas com condutividade baixa. Rhabdolichops lundbergi ocorre quase exclusivamente nas calhas principais dos rios de aguas brancas e em canais de varzea (paranas) com condutividade alta. Rhabdolichops nigrimans e R. lundbergi formam um clado monofiletico que representa um grupo irmao das demais especies de Rhabdolichops. Estas duas especies apresentam fenotipos transicionais entre os generos Eigenmannia e Rhabdolichops. Rhabdolichops nigrimans apresenta um dimorfismo sexual acentuado no comprimento do filamento caudal. Contudo, R. lundbergi nao possui esta caracteristica. Rhabdolichops navalha e R. stewarti sao especies irmas dentro de um grupo monofiletico constituido por R. eastwardi e R. caviceps + R. troscheli. Rhabdolichops navalha apresenta uma morfologia unica do orgao eletrico onde a sua margem posterior finda-se abruptamente e e substituida, posteriormente, por um tecido rigido e nao-eletrogenico.
ISSN:0045-8511
DOI:10.1043/0045-8511(2006)006[0027:TNSOTN]2.0.CO;2