Abstract
Three local geographically isolated populations of C. nattereri from Brazil were analyzed. A different diploid number was detected in each sample, i.e., 2n=40 (Bonito river), 2n=42 (Biguá river), and 2n=44 (Tinguá river). Analysis of Nucleolus Organizer Regions showed that the Rio de Janeiro samples have one chromosome pair with NOR, while the Sao Paulo sample has two. In general, the NORs are C-band positive. Analysis of constitutive heterochromatin distribution showed some similarities between two of the populations. The different chromosome formulae identified permitted the characterization of the occurrence of three cytotypes for C. nattereri, suggesting that these cytotypes may actually be different species.
