NEW OCCURRENCE OF A MACRO-B-CHROMOSOME IN ASTYANAX-SCABRIPINNIS-PARANAE (PISCES, CHARACIFORMES, CHARACIDAE)

Cytogenetic studies performed on 17 specimens (11 females and six male s) of Astyanax scabripinnis paranae from the Cascatinha stream showed that this population has 2n=50 chromosomes (8M+22SM+10ST+10A), two chr omosome pairs with NORs and conspicuous C-band positive blocks in the terminal position of the long arm of five chromosome pairs. Three fema les presented 2n=51 chromosomes and the extra chromosome was a large m etacentric similar in size and morphology to the first chromosome pair in the karyotype. This accessory chromosome was entirely heterochroma tic in C-banded metaphases, which permitted its classification as a su pernumerary chromosome. Some aspects related to the morphology of such macro B-chromosomes are discussed.