| Two Siluriformes species endemic to the São Francisco River basin were characterized by conventional and differential cytogenetic analyses involving C-banding, Ag-nucleolar organizer region (NOR) and chromomycin A3 (CMA3) staining, and FISH (fluorescent in situ hybridization) with 18S and 5S rDNA probes. Conorhynchus conirostris presents a higher diploid number (2n = 60) than those detected in Pimelodidae representatives, whereas Lophiosilurus alexandri, with a karyotype of 2n = 54 chromosomes, presents a chromosomal constitution similar to that found in the family Pseudopimelodidae. Plesiomorphic characteristics such as single NORs at terminal positions are found in both species, as revealed by CMA3 and silver nitrate staining, and FISH with a 18S rDNA... |
