Aspectos citogenéticos de peixes das famílias Gempylidae e Balistidae do Arquipélago de São Pedro e São Paulo, região Meso-Atlântica

Abstract

Marine fishes, over all those inhabitating on pelagic environments or large depths, they usually have large gaps in cytogenetic information, restricting its use in evolutionary approaches. Among these groups, small families like Gempylidae, with 16 genera and 26 species and relative importance in commercial fishery, didn’t have any chromosomal data. Likewise, the family Balistidae, with 42 species, presents less than half of the species with known karyotypes. Aiming to increase the knowledge of the cytogenetic aspects of marine fish, mainly inhabitants of insular regions of the South Atlantic, were analyzed the species Promethichthys prometheus and Ruvettus pretiosus (Gempylidae) and Canthidermis maculata and C. sufflamen (Balistidae), from the Archipelago of São Pedro and São Paulo, Meso-Atlantic region. Cytogenetic analysis used conventional methodologies (Giemsa staining, Ag-RON staining and Cbanding), staining with base-specific fluorochromes (CMA3/DAPI) and repetitive sequence mapping of 18S rDNA, 5S rDNA, microsatellite sequences (CA)15 and (GA)15, transposon Tol2 and retrotransposon Rex3, through fluorescent in situ hybridization (FISH). Promethichthys prometheus and R. pretiosus have 2n=48 chromosomes, however, they differ considerably regarding the karyotype formula (NF=84 and NF=50, respectively). The chromosome mapping of the different classes of repetitive DNA, suggest a small microstructural divergence in the chromosomes. On the other hand, C. maculata (2n=44 and NF=56) and C. sufflamen (2n=44 and NF=58), exhibit reduced karyotypes, as result of in tandem fusions, followed by a low internal reorganization of the chromosomes. These first results for the Gempylidae family, indicate marked structural chromosomal diversification in these deep-water inhabitants, while the patterns found in the species of Balistidae, corroborate the role of fusions in their karyotype evolution. The expansion of cytogenetic data for these species confirms the remarkable karyotype diversity and particular karyoevolutionary trends of some groups of marine fish.