Karyotypes after conventional staining and C-banding – Platydoras armatulus a Giemsa staining reveals 2n=58 (22m+14sm+18st+4a) and 1-3 B chromosomes b C-banding pattern characterized by the many heterochromatin blocks in different positions, including in B chromosomes. Pterodoras granulosus c Giemsa staining also reveals 2n=58 but with distinct karyotypic formulae: 16m+16sm+14st+12a and 1 B chromosome d a few heterochromatin blocks was evidenced after C banding, observe the B chromosome totally heterochromatic. Ossancora punctata e After Giemsa staining it was observed 2n=66 (12m+8sm+6st+40a), the high number of subtelocentric and acrocentric chromosomes is a remarkable feature of this specie f C-banding reveals heterochromatin regions in terminal position and in B chromosomes.