Paracentric Inversions Differentiate the Conservative Karyotypes in Two Centropomus Species (Teleostei: Centropomidae).

Centropomus is the sole genus of the Centropomidae family (Teleostei), comprising 12 species widely distributed throughout the Western Atlantic and Eastern Pacific, with 6 of them occurring in the Western Atlantic in extensive sympatry. Their life history and phylogenetic relationships are well characterized; however, aspects of chromosomal evolution are still unknown. Here, cytogenetic analyses of 2 Centropomus species of great economic value (C. undecimalis and C. mexicanus) were performed using conventional (Giemsa, Ag-NOR, and fluorochrome staining, C- and replication banding) and molecular (chromosomal mapping of 18S and 5S rDNA, H2A-H2B and H3 hisDNA, and (TTAGGG)n repeats) approaches. The karyotypes of both species were composed of 48 solely acrocentric chromosomes (2n = 48; FN = 48), but the single ribosomal site was located in varying positions in the long arms of the second largest chromosome pair. Replication bands were generally similar, although conspicuous differences were observed in some chromosome regions. In both species, the histone H3 genes were located on 3 apparently homeologous chromosome pairs, but the exact position of these clusters differed slightly. Interspecific hisDNA and rDNA site displacements can indicate the occurrence of multiple paracentric inversions during the evolutionary diversification of the Centropomus genomes. Although the karyotypes remained similar in both species, our data demonstrate an unsuspected microstructural reorganization between them, driven most likely by a series of paracentric inversions.