CHROMOSOME DIVERGENCES BETWEEN 2 SYMPATRIC CHARACID FISHES OF THE GENUS BRYCONAMERICUS

Cytogenetic studies were performed on two sympatric species of Brycona mericus which are awaiting more precise taxonomic identification. Alth ough both Bryconamericus sp A and Bryconamericus sp B had a chromosome number equal to 52 chromosomes, their karyotypic structures varied wi dely. The two species presented multiple nucleolar organizer regions ( NORs), at times varying in size. Centromeric heterochromatin was the m ost frequent type in the species studied and C banding showed no signi ficant differences between karyotypes. The data permitted us to propos e that non-Robertsonian chromosome rearrangements of the pericentric i nversion type led to the differences between the two species of Brycon americus.