Possible Common Origin of B Chromosomes in Neotropical Fish (Siluriformes, Auchenipteridae) Reinforced by Repetitive DNA Mapping

HIGHLIGHTS

B chromosomes of different species have a common origin.

B chromosomes similarities suggest Parauchenipterus diagnosis is likely not valid.

Abstract

The aim of this paper was to present the second case of B chromosomes in Auchenipteridae (Trachelyopterus sp.), and to test the hypothesis that the B chromosomes of this species and Parauchenipterus galeatus might have a common origin, since these two species have phylogenetic proximity. Both species have 58 chromosomes in the A complement, heterochromatin preferentially located at terminal region of the most of chromosomes, simple Ag-NORs located at the short arm of a subtelocentric pair, which was confirmed by hybridization with 18S rDNA, two submetacentric pairs carrying 5S rDNA sites, and presence of B chromosomes. The B chromosomes of the two species are small, metacentric, and almost totally heterochromatic, with variation of number intra and interindividual. In addition, for the first time in fish, the telomeric sequence [TTAGGG]_n was dispersed along the B chromosomes (both species). The [GATA]_n microsatellite were scattered in all chromosomes of the A complement and absent in the B chromosomes, in both species. These aspects confirm the phylogenetic proximity between the genus Parauchenipterus and Trachelyopterus, and they suggest the hypothesis that the B chromosomes of the two species might have common origin, previous to the diversification of these genera.

Keywords:
chromosome evolution; [TTAGGG]_n; [GATA]_n; Parauchenipterus; Trachelyopterus