NATURAL TRIPLOIDY IN ASTYANAX-SCABRIPINNIS (PISCES, CHARACIDAE) AND SIMULTANEOUS OCCURRENCE OF MACRO B-CHROMOSOMES

The occurrence of natural triploidy in two specimens of Astyanax scabr ipinnis collected in the Araqua river and in the Corrego das Pedras st ream, respectively, is noticed. The triploid specimen from the Araqua river presented one macro B-chromosome and the triploid specimen from Corrego das Pedras stream presented two macro B-chromosomes. The C-ban ding performed in the specimen from the Araqua river confirmed the tri ploidy and showed that the macro B-chromosome was entirely heterochrom atic. Ag-NOR characterization showed two chromosomes involved in the n ucleolar activity in both specimens. Some aspects related to the origi n of triploid fishes are described.