Molecular cytogenetic analysis of Haemulidae fish (Perciformes): Evidence of evolutionary conservation

Several fish species belonging to the family Haemulidae present a karyotype consisting of 48 acrocentric chromosomes (FN = 48), and apparently similar chromosomal microstructure, especially in genus Haemulon, representing a striking example of intrafamiliar chromosomal conservation. In this study, a more detailed cytogenetic analysis of the species Conodon nobilis and Pomadasys corvinaeformis was performed using C-banding, Ag-NOR, DAPI/CMA₃ staining, in situ digestion by distinct endonucleases and double-FISH to map the 18S and 5S ribosomal genes. Both species showed a similar karyotypic macrostructure with 2n = 48 acrocentric chromosomes and active ribosomal sites at interstitial position on long arms of chromosomal pair 18 and 24 in P. corvinaeformis and C. nobilis, respectively. These sites were the only CMA₃⁺/DAPI^-regions in the karyotype. Digestion with restriction enzymes revealed a low number of digestion sites in the heterochromatic segments of both species. The data indicate some degree of interspecific evolutionary diversification At the microstructural level, incorporated in a general pattern of extensive karyotypic conservatism. Thus, the interspecific reproductive isolation leading to phyletic diversification apparently occurred without the contribution of conspicuous karyotypic changes.