Multigene analysis of the catfish genus Trichomycterus and description of a new South American trichomycterine genus (Siluriformes, Trichomycteridae)

Axel Makay Katz,Maria Anais Barbosa,Wilson José Eduardo Moreira Da Costa,José Leonardo De Oliveira Mattos

doi:10.3897/zse.94.29872

Abstract

Trichomycterus comprises about 170 valid species, but its monophyly has been challenged in the last decades. Bayesian Inference and Maximum Likelihood analyses comprehending mitochondrial genes COI and CYTB and nuclear genes GLYT, MYH6 and RAG2 from 71 Trichomycterinae terminal taxa and eight outgroups were performed. The analyses highly supports a clade containing Trichomycterusnigricans, the type species of the genus, and several other congeners endemic to eastern and northeastern Brazil, herein considered as the genus Trichomycterus, the sister clade the southern Brazil and adjacent areas clade; the latter clade comprises two subclades, one comprising species of the genus Scleronema and another comprising species previously placed in Trichomycterus, herein described as a new genus. Cambevagen. n. is distinguished from all other trichomycterines by the presence of a bony flap on the channel of the maxillo-dentary ligament, the interopercle shorter than the opercle, a deep constriction on the basal portion of the antero-dorsal arm of the quadrate, absence of teeth in the coronoid process of the dentary, the maxilla shorter than the premaxilla, the cranial fontanel extending from the the medial posterior of frontal to the medial region of supraoccipital, and absence of the postorbital process of the sphenotic-prootic-pterosphenoid.

Highlights

Siluriformes is among of the most diverse vertebrate orders, with about 3700 species in 39 families (Nelson et al 2016, Frick et al 2018)
The objective of this paper is to provide the more inclusive molecular based phylogenetic analysis of Trichomycterus, assigning the phylogenetic position of its type species, Trichomycterus nigricans Valenciennes, 1832 and describing a new genus, sister to Scleronema, that was hidden under the lack of consistent information about Trichomycterus relationships
The first one, the trichomycterine clade a, is highly supported in both analyses (Figs 1, 2) and comprises species geographically restricted to an area encompassing eastern, south-eastern and southern Brazil, which have been traditionally placed in two genera, Scleronema and Trichomycterus

Summary

Introduction

Siluriformes (catfishes) is among of the most diverse vertebrate orders, with about 3700 species in 39 families (Nelson et al 2016, Frick et al 2018). Trichomycteridae, the second most diverse catfish family, with about 300 species (Frick et al 2018 ), is characterized by having a modified opercular system, involving the presence of odontodes in the interopercular and opercular bones (Baskin 1973, de Pinna 1992, 1998). It occurs between southern Central America, in Costa Rica, and southern South America, in Patagonia (Baskin 1973, de Pinna 1998), exhibiting an impressive species diversity and endemism around higher elevations (de Pinna 1992).

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