Chromosomal analysis of Centromochlus heckelii (Siluriformes: Auchenipteridae), with a contribution to Centromochlus definition

Samantha Kowalski,Roberto Laridondo Lui,Maelin Da Silva,Josiane Baccarin Traldi,Eliana Feldberg,Amanda De Souza Machado,Vladimir Pavan Margarido,Leonardo Marcel Paiz

doi:10.1590/1982-0224-2020-0009

Abstract

ABSTRACT Historically, there are divergences in the species allocation between Centromochlus and Tatia. This study aimed to generate the first cytogenetic data about Centromochlus and, by analyzing a population of Centromochlus heckelii from the Amazon River basin, to contribute as evidence to a historical taxonomic dilemma. Diploid number of 46 chromosomes and a heteromorphic pair was found in the female karyotypes, thus characterizing a ZZ/ZW sex chromosome system. Pale blocks of heterochromatin were located in centromeric regions of some chromosomes; however, the exclusive female chromosome (W) is almost entirely heterochromatic. AgNORs were detected in terminal position on the short arms of one acrocentric pair in males and two chromosome pairs in females, the acrocentric plus the sex chromosome pair. Notable differences between Centromochlus heckelii and previous data about species of Tatia are: lower diploid number, presence of a sex chromosome system and multiple AgNORs in Centromochlus, while species of Tatia have simple AgNORs and the absence of acrocentric chromosomes. Results in this study show that chromosomal markers could contribute as evidence to taxonomic delimitation studies.

Highlights

The Neotropical region is characterized by great biodiversity, and South America has the richest freshwater and marine ichthyofauna in the world (Reis et al, 2016)
Cytogenetic analysis of Centromochlus heckelii data for Tatia (Lui et al, 2013a), this study aimed to describe the first chromosomal data for Centromochlus
Divergent data are observed in Ageneiosus Lacepède 1803, with 56 chromosomes (Fenocchio, Bertollo, 1992; Lui et al, 2013b). This difference can be related to a chromosomal fusion event, confirmed by the presence of ITS (Interstitial Telomeric Sequence) in Ageneiosus inermis (Linnaeus, 1766) (Lui et al, 2013b)

Summary

Introduction

The Neotropical region is characterized by great biodiversity, and South America has the richest freshwater and marine ichthyofauna in the world (Reis et al, 2016). Auchenipteridae consists of 26 genera and 126 species (Fricke et al, 2020) divided into two subfamilies (Centromochlinae and Auchenipterinae), which present some historical internal phylogenetic incongruities (Ferraris, 1996; Soares-Porto, 1998). This family gathers small to medium size fishes, with suborbital groove to lodge maxillary bone and anal fin of male with intromittent organ (Calegari et al, 2019). They present internal insemination and a remarkable sexual dimorphism related to anal fin modification and other parts of the body, such as dorsal and pelvic fins, and maxillary barbels (Birindelli, 2014)

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