Contributions to the taxonomy of Trachelyopterus (Siluriformes): comparative cytogenetic analysis in three species of Auchenipteridae

Dayane Petik Dos Santos,Roberto Laridondo Lui,Vladimir Pavan Margarido,Denise Felicetti,Daniel Rodrigues Blanco,Lucas Baumgärtner,Orlando Moreira-Filho

doi:10.1590/1982-0224-2020-0115

Abstract

ABSTRACT Auchenipteridae is divided into subfamilies Centromochlinae and Auchenipterinae. Parauchenipterus is included in the latter and is subject of taxonomic discussions concerning its validation or synonymization with Trachelyopterus. Herein, three species from two hydrographic basins were cytogenetically analyzed: Parauchenipterus striatulus from Doce River and two sympatric species, P. galeatus and Trachelyopterus coriaceus, from the Araguaia River. Diploid number of 58 chromosomes was verified for all species, but P. striatulus has different karyotype formula from the others. The three species have heterochromatin located in terminal regions of almost all chromosomes and in pericentromeric region on acrocentric chromosomes. Simple NORs was verified on a subtelocentric chromosome for all species. 5S rDNA sites were detected in three submetacentric chromosome pairs in P. striatulus; in a metacentric chromosome pair and submetacentric pair in T. coriaceus; and in one metacentric chromosome pair in P. galeatus. The similarities found in the karyotypes of the three species suggest the existence of only one genus, Trachelyopterus; therefore, our data refutes the validation of Parauchenipterus. Moreover, the differences in 5S rDNA distribution in P. galeatus in comparison with other populations already studied, indicate the existence of a new taxonomic unit, which suggests a species complex in P. galeatus.

Highlights

Auchenipteridae belongs to the order Siluriformes and contains 25 genera and 126 species (Fricke et al, 2021) divided into two subfamilies: Centromochlinae and Auchenipterinae, the latter including the species of Trachelyopterus Valenciennes, 1840 and Parauchenipterus Bleeker, 1862
C-banding technique evidenced pale heterochromatin in terminal regions of almost all chromosome pairs (Fig. 1D). 18S rDNA-Fluorescent in situ Hybridization (FISH) confirmed previous findings by AgNO3 staining and revealed these sequences only on pair 23. 5S rDNA-FISH detected these sequences in three submetacentric pairs, on the short arm of the pair 10 and 13, and on the long arm of the pair 15 (Fig. 1G)
C-banding evidenced pale heterochromatin in terminal regions of almost all chromosome pairs (Fig. 1E). 18S rDNA-FISH confirmed previous finding by AgNO3 staining, simple NORs on pair 24. 5S rDNA-FISH detected these sites on short arm of the metacentric chromosome pair 3 (Fig. 1H)

Summary

Introduction

Auchenipteridae belongs to the order Siluriformes and contains 25 genera and 126 species (Fricke et al, 2021) divided into two subfamilies: Centromochlinae (with nine genera) and Auchenipterinae, the latter including the species of Trachelyopterus Valenciennes, 1840 and Parauchenipterus Bleeker, 1862. Several synapomorphies support the hypothesis of a monophyletic family, and its main characteristics are sexual dimorphism and internal insemination (Akama, 2004; Birindelli, 2014). Cytogenetic analyzes in this family are scarce and restricted to Ageneiosus Lacepède, 1803, Auchenipterus Valenciennes, 1840, Glanidium Lütken, 1874, Tatia Miranda Ribeiro, 1911 and Parauchenipterus (Tab. 1). Exceptions to the most common in the group include Ageneiosus, Tympanopleura, Tatia neivai (Ihering, 1930) and Centromochlus Kner, 1858

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