Chromosomal characterization in two species of an Astyanax bimaculatus complex (Characidae, Characiformes) using different techniques of chromosome banding.

Astyanax has been the subject of extensive cytogenetic studies due to its wide karyotypic diversity. This genus comprises species complexes, namely groups of fish of difficult morphological differentiation, such as the bimaculatus complex, which includes the characids with a rounded humeral spot. Thence, the present study proposed to accomplish a cytogenetic characterization of two species of this complex: A.

Chromosome studies of Astyanax jacuhiensis Cope, 1894 (Characidae) from the Tramandai River Basin, Brazil, using in situ hybridization with the 18S rDNA probe, DAPI and CMA3 staining.

The genus Astyanax comprises 86 species of fish distributed in Brazilian river basins and is considered of the Incertae sedis group within the family Characidae. This study presents an analysis of 12 specimens of Astyanax jacuhiensis from the Tramandai River Basin, RS Brazil: 6 from the Maquiné River and 6 from the Quadros Lagoon. All specimens showed a diploid number equal to 50 chromosomes with different karyotypic formula between the two localities.