Two new species of Trichomycterus (Siluriformes: Trichomycteridae) from the Rio Itabapoana Basin, south-eastern Brazil

Abstract

Streams in the Atlantic Forest of Brazil are home to a great diversity of endemic freshwater fishes, but some fish groups are still poorly known. In the last 22 years, our field inventories have recorded some species of the mountain catfish genus Trichomycterus that are endemic to the Rio Itabapoana Basin, among which two were not still described. Herein, we provide formal descriptions for these two species. One of these species is a member of the NMM-clade of the subgenus Cryptocambeva and the other one belongs to the beta-clade of the subgenus Psammocambeva. Both species are diagnosed by an exclusive combination of character states of the external morphology and osteology. This study indicates that the number of endemic trichomycterine species in the Rio Itabapoana Basin, presently five, is larger than in any other small coastal river basin of the Atlantic Forest. A key for identification of species of Trichomycterus from this basin is provided. We discuss two factors that may be responsible for the relatively high concentration of trichomycterines in this basin: streams draining separate mountain ranges or possible past connections with two neighbouring larger basins, the Rio Doce and the Rio Paraíba do Sul basins.

Keywords

• Atlantic Forest
• Cryptocambeva
• mountain biodiversity
• Psammocambeva