Karyotypic Diversification in Two Species (Characiformes, Anostomidae) Inferred from Localization of Repetitive DNA Sequences.

Anostomidae species have conserved diploid numbers (2n = 54), although comparative cytogenetic studies have demonstrated chromosomal rearrangements occurrence among them, especially in repetitive DNA rich regions. The location and distribution of ribosomal DNA (rDNA) and () multigene families are highly dynamic in the genomes of several organisms. In this study, we located the rDNA and s sites in two populations of and a sample of to infer their chromosomal changes in the evolutionary lineages. Both species of shared 2n = 54 chromosomes with the presence of ZZ/ZW sex chromosome system, but they diverged in relationship to the location of 5S and 45S rDNAs as well as the distribution of sites. The characterization of the analyzed sequences revealed the presence of complete rDNA and sequences as well as containing transposable elements (TEs) and microsatellite repeats. After chromosomal mapping, the sequences encompassing TEs proved to be dispersed through autosomes and accumulated on sex chromosomes. The data demonstrate that intra- and interspecific chromosomal changes occurred involving the multigene family's sites in karyotypes. Furthermore, we detected TE-like sequences in the differentiation of sex chromosome systems in and .