﻿A new catfish of the genus Trichomycterus from the Rio Paraíba do Sul Basin, south-eastern Brazil, a supposedly migrating species (Siluriformes, Trichomycteridae)

Wilson J E M Costa,Axel M Katz

doi:10.3897/zse.98.72392

Abstract

A new species of the catfish genusTrichomycterusis described from the Rio Paraíba do Sul, south-eastern Brazil. This species exhibits some morphological character states that are unique amongst congeners, including a robust opercle and a long interopercle with numerous odontodes (50–60 opercular and 90–100 interopercular), a black bar on the basal portion of the caudal fin and a dark brown flank with a well delimited dorsal yellow stripe. It also exhibits some morphological traits that are uncommon amongst congeners, such as the presence of nine pectoral-fin rays. The presence of a shallow hyomandibular outgrowth and a ventrally expanded pre-opercular ventral flap suggests that this species is closely related toT. melanopygius,T. pradensisandT. tete. The new species also differs fromT. melanopygius,T. pradensisandT. teteby having an emarginate caudal fin and a single median supra-orbital pore S6. Anecdotal evidence suggests thatT. largoperculatusandT. pradensishave migratory habits, a condition not previously reported for eastern South American trichomycterines.

Highlights

The Trichomycterinae, one of the eight subfamilies of the Neotropical catfish family Trichomycteridae, comprises a diversified group with most species inhabiting swift freshwater environments between southern Central America and southern South America (Katz et al 2018)
These conditions may be present in different trichomycterine lineages, the occurrence of these morphological character states is uncommon amongst eastern South American trichomycterines
According to Costa et al (2020a), an apomorphic concave posterior margin of the caudal fin yielding an emarginate shape, is synapomorphic for species of the T. nigricans group, but an emarginate caudal fin is present in T. astromycterus Reis, de Pinna & Pessali, 2020, a species with uncertain phylogenetic position (Reis et al 2020; Costa 2021)

Summary

Introduction

The Trichomycterinae, one of the eight subfamilies of the Neotropical catfish family Trichomycteridae, comprises a diversified group with most species inhabiting swift freshwater environments between southern Central America and southern South America (Katz et al 2018). Recent studies, using molecular evidence, have consistently indicated that different lineages involving over 150 species, formally placed in Trichomycterus, are closer to distinct trichomycterine genera, corroborating the former view about the paraphyletic nature of Trichomycterus (Ochoa et al 2017; Katz et al 2018; Costa et al 2021a, 2021b). This problem was tentatively solved, by restricting Trichomycterus We provide a formal description for the new species and discuss morphological variation considered relevant for its phylogenetic positioning, as well as migration in trichomycterines

Material and methods

Results

Discussion