Morphology and distribution of the cave knifefish Eigenmannia vicentespelaea Triques, 1996 (Gymnotiformes: Sternopygidae) from Central Brazil, with an expanded diagnosis and comments on subterranean evolution

Maria Elina Bichuette,Eleonora Trajano

doi:10.1590/s1679-62252006000100011

Abstract

We present herein data on morphology and distribution of the cave knifefish Eigenmannia vicentespelaea Triques, 1996, from the São Domingos karst area, Central Brazil, comparing it to the epigean (surface) species, Eigenmannia sp., found in the same area (but not syntopic with E. vicentespelaea) and also with congeners from other localities. Collecting sites comprising epigean and subterranean stream reaches in São Domingos were sampled during the dry seasons of 1999, 2000, and 2001 using several methods. Preserved specimens of E. vicentespelaea (n=25, including holotype and paratype) and of Eigenmannia sp. (n=15) were compared with focus on morphometric characters, body pigmentation and eye condition. A combination of characters separates E. vicentespelaea from Eigenmannia sp. and other congeners: the length from the tip of the snout to the posterior of the anal fin base, ocular diameter: head length and pre-anal distance: head length proportions, and body pigmentation. A wider morphometric variation in E. vicentespelaea is described than that reported in the original description (based on two specimens).

Highlights

Electric fishes of the Order Gymnotiformes are an important component of the night-active ichthyofauna in South and Central America, corresponding to a monophyletic group based, among other characters, on the ability of producing and detecting weak electric fields (Alves-Gomes et al, 1995; Albert & Campos-da-Paz, 1998; Albert, 2001)
We present morphometric and distributional data on E. vicentespelaea, comparing it to the epigean species Eigenmannia sp. from the same area and congeners from other regions
For the comparative study of the external morphology and morphometry of Eigenmannia species, different localities comprising both epigean and subterranean streams were sampled during the dry seasons of 1999, 2000, and 2001 using different collecting methods

Summary

Introduction

Electric fishes of the Order Gymnotiformes are an important component of the night-active ichthyofauna in South and Central America, corresponding to a monophyletic group based, among other characters, on the ability of producing and detecting weak electric fields (Alves-Gomes et al, 1995; Albert & Campos-da-Paz, 1998; Albert, 2001) These fishes are distributed between 35oS, in Argentina, and 18oN, in Mexico (Eigenmann & Allen, 1942; Bullock et al, 1979; Mago-Leccia, 1994), with some genera occurring almost exclusively in deep waters of the Amazon basin. The monophyly of Eigenmannia Jordan & Evermann, 1896 was not demonstrated yet and its taxonomy remains confused (Mago-Leccia, 1978; Lundberg & Mago-Leccia, 1986; Albert, 2001)

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Conclusion