A new species of Trichomycterus Valenciennes 1832 (Trichomycteridae: Siluriformes) from the Rio Doce drainage with remarkable similarities with Bullockia and a CT‐scan survey

Abstract

A new species of Trichomycterus is described from rocky and psammic sectors near the main channel of the middle and upper Rio Doce basin in Southeastern Brazil.Trichomycterus astromycterus n. sp., is distinguished from all congeners by a number of autapomorphic characters, such as the distally expanded maxilla; the short and thick mesethmoid cornua; and the elongated anterior process of the vomer. Additional characters (short barbels, large head, 33 vertebrae, ii+8 or ii+9 dorsal-fin rays, nine dorsal-fin pterygiophores, markedly enlarged lips, narrow caudal peduncle, bilobed caudal fin with the lower lobe longer than the upper one) also distinguish the new species from all its congeners in Southeastern Brazil and from most congeners anywhere. Examination of internal anatomy reveals that T. astromycterus shares some intriguing characteristics with the austral genus Bullockia Arratia et al., 1978. However, the phylogenetic significance of such similarities is still uncertain and will require further comparative study. For this reason, the new species is provisionally included in the all-encompassing genus Trichomycterus. An osteological description is presented on the basis of CT-scan imaging and cleared and stained specimens. K E Y W O R D S

Emerging patterns in phylogenetic studies of trichomycterid catfishes (Teleostei, Siluriformes) and the contribution of Andean diversity

“…Although our results are consistent with the expectations from the current taxonomy, in that Bullockia is resolved as phylogenetically distinct, subtended by a relatively long branch with respect to its closest relatives (clade 7; Figure 1), the morphological distinctiveness and uniqueness of this genus was recently brought into question by Reis et al. (2019) in their description of a new Trichomycterus species from southern Brazil, Trichomycterus astromycterus , which is morphologically very similar to Bullockia (such as the proportionally larger eyes; number of lateral line sensory pores 3–5; shape of the premaxilla tapering laterally; and the long posterior process of the autopalatine). Despite acknowledging a number of remarkable similarities between T .…”

“…astromycterus and Bullockia —suggestive of a close relationship between the two, possibly even congenericity—Reis et al. (2019) assigned this novel species to Trichomycterus while admitting the provisional nature of this nomenclatural decision pending a better understanding of phylogenetic relationships. Regardless of nomenclatural considerations, the evolutionary distinctiveness of Bullockia , as implied by our results, might be an artefact of the pragmatically inevitable undersampling of Trichomycterus diversity.…”

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

“…In the over 40 species included in the clade comprising Cambeva and Scleronema, which is sister to Trichomycterus s.s., the caudal fin is always truncate or subtruncate and there are eight rays or less in the pectoral fin, never nine (Costa et al 2020a). 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 (subgenus Trichomycterus), but an emarginate caudal fin is also present in T. astromycterus Reis, de Pinna & Pessali, 2020, a species with uncertain phylogenetic position (Reis et al 2020;Costa 2021). The T. nigricans group is a clade highly supported by molecular data (Costa et al 2020b), comprising T. caipora Lima, Lazzarotto & Costa, 2008, T. immaculatus (Eigenmann & Eigenmann, 1889, T. nigricans and T. santaeritae (Eigenmann, 1918) Interestingly, all of these four species also possess nine pectoral-fin rays, considered to be another synapomorphy for the T. nigricans group (Costa et al 2020a), although independently occurring in T. giganteus Lima & Costa, 2004 of the subgenus Megacambeva Costa, 2021 and T. pradensis Sarmento-Soares, Martins-Pinheiro, Aranda & Chamon, 2005 of the subgenus Psammocambeva Costa, 2021 (Costa et al 2020a, b;Costa 2021).…”

Parasites of Cambeva davisi (Siluriformes: Trichomycteridae) from the Cascavel stream, Neotropical area

“…Among the least studied fish from streams in the Iguaçu River basin are those of the family Trichomycteridae Bleeker, 1858, composed of 366 species (Froese and Pauly 2020) of small nonparasitic catfishes, with Trichomycterinae Bleeker, 1858 being the most specious subfamily, represented by 262 valid species (Fricke et al 2020). The proposal for the monophyly of Trichomycterinae clade based on morphological data has been contested, and recent studies based on morphological and molecular data have been performed in order to resolve this incongruity (Ochoa et al 2017(Ochoa et al , 2020Katz et al 2018;Reis et al 2019). In this context, Cambeva Katz, Barbosa, Mattos & Costa, 2018 have been recently described, and includes 26 species previously allocated to Trichomycterus Valenciennes, 1832 (Fricke et al 2020), including Cambeva davisi (Haseman, 1911) (= Trichomycterus davisi), the type species of the genus (Katz et al 2018).…”