A new rare catfish species from southeastern Brazil provides insights into the origins of similar colour patterns in syntopic, distantly related mountain trichomycterines (Siluriformes, Trichomycteridae)

By

Costa, Wilson J. E. M. (Wilson José Eduardo Moreira)
Feltrin, Caio
Mattos, José Leonardo
Katz, Axel

Type

Article

Date of Publication

2024

Original Publication

Zoosystematics and evolution

Volume

100

Series / Issue

Issue: 2

Pages

755--767

Subjects

Atlantic forest , molecular systematics , mountain biodiversity , Rio Paraíba do Sul basin , Serra da Mantiqueira

Contributed by

Pensoft Publishers

Language

English

Published by

Sofia Pensoft

Identifiers

DOI: https://doi.org/10.3897/zse.100.118000

 

Abstract

Colour patterns are diverse in trichomycterine catfishes and are often used to diagnose species. Here, we analyse the first case of adults of two syntopic species of Trichomycterus sharing nearly identical colour patterns: a rare new species of the subgenus Paracambeva and Trichomycterus maculosus, a distantly related species of the subgenus Trichomycterus. Both species are endemic to the upper Rio Paraíba do Sul basin (RPSB), which had a different course until the Tertiary period and is situated within the Southeastern Brazilian Continental Rift, mostly active in the Eocene-Oligocene. A time-calibrated multigene analysis, 3144 bp, supported the new species as sister to Trichomycterus itatiayae, both comprising a lineage with Middle Miocene age, when that colour pattern would have first arisen. The new species is diagnosed by characters from the latero-sensory system and bone morphology. Our results, combined with available biogeographical data, indicated the colour pattern of T. maculosus arising in the Late Pliocene, following the dispersal of its group to the upper RPSB after river course changing. Two hypotheses for the independent origin of the same colour pattern are discussed. First, a case of evolutionary convergence for adaptation to live on a similarly coloured gravel substrate, giving some cryptic advantage against predators. Second, mimetic association through anti-predation features. In the latter case, although trichomycterids lack fin spines to inoculate venom as in other catfishes, the species here studied have a supposed axillary gland above the pectoral fin, just posterior to the opercular odontodes, but with properties and functions still unknown.