Karyotypic study of some species of family Mochokidae (Pisces, Siluriformes): evidence of female heterogamety

Abstract

Nine mochokid species, Hemysynodontis rnembranaceus, Synodontis bastiani, S. budgetti, S. courier;, S. filamentosus, S. orellifer. S. schall. S. sorex. S. violaceus, were investigated to determine their karyotype. Like many of the studied siluriforms, they were shown to possess 2N=54 or 2N=56 chromosomes, with a fundamental number varying from 95 to 102. In addition, our study revealed the existence of heteromorphic chromosomes in all the studied females of each species. These findings are discussed in relation to chromosome evolution within the siluriforms, and to differentiation of sex chromosomes in fishes.