Cytologia 69(4): 419–424, 2004

The cytogenetic analyses showed that Pseudopimelodus mangurus has a diploid number of 2n 54 chromosomes (6M, 26SM, 12ST and 10A), single Ag-NORs on the short arm of a middle-sized ST pair, identified as pair 19, and a very small amount of C-band positive segments in two chromosome pairs. The Ag-NORs are C-band positive. The staining of the chromosomes of P. mangurus with CMA3 reveled the occurrence of bright signals corresponding to the Ag-NORs segments, to the C-band positive segments and also to some C-band negative segments. The occurrence of a diploid number of 2n 54 in all species of the family Pseudopimelodidae and its absence among representatives of Pimelodidae and Heptapteridae, two related families previously considered, reinforces the hypothesis that Pseudopimelodidae is a monophyletic group.