Karyotypic Studies and Cytotaxonomic Considerations on Callichthys callichthys (Pisces, Siluroidei) from Argentina

Abstract

We studied cytogenetically a population of Callichthys callichthys from Argentina. It showed three different cytotypes. The basic chromosome number observed in this population was 2n=56. The presence in some individuals of one or two metacentric accesory chromosomes originated polymorphic forms with 2n=57 (56+1) and 2n=58 (56+2). C-bands were observed in centromeric and pericentromeric regions. The NORs were located in terminal position in the short arms on a ST chromosome pair. The successive aplication of these techniques evidence the correlation between NORs and constitutive heterochromatic regions.
On the basis of available data we suggest that 2n=56 may be the basic chromosome number for Callichthys callichthys. All the different cytotypes described at the present could be derivated forms.