Contribuições aos estudos citogenéticos em algumas espécies de 5 famílias de Siluriformes do rio São Francisco.
Resumo
Cytogenetic studies involving representatives of the order Siluriformes found in the
São Francisco River basin continue practically inexistent. Therefore, the main objective of the
present work was to contribute to the cytogenetical knowledge of the fish species belonging to
the following families: Auchenipteridae, Doradidae, Heptapteridae, Pimelodidae and
Pseudopimelodidae, all found in the São Francisco River in the Três Marias region MG. In
order to accomplish this, conventional chromosome analysis, different bandings and
fluorescent in situ hybridization with 5S AND 18S rDNA probes were used. A great part of
the cytogenetical data obtained consists in the first chromosomal characterization of many of
the analyzed species, emphasizing the need for more studies of this sort within this group. A
few chromosomal evolution tendencies were also detected for species that already possessed
previous cytogenetic information, which permits a larger comprehension of the differentiation
processes and karyotypic evolution. The data here presented give clues regarding the great
diversity of the ichthyofauna of the São Francisco River and regarding the possible effects of
factors that influence in the diversification and in the high degree of endemism of the fish
belonging to this basin.