COMPARATIVE CYTOGENETIC AND MORPHOLOGICAL ANALYSIS OF ASTYANAX-SCABRIPINNIS PARANAE (PISCES, CHARACIDAE, TETRAGONOPTERINAE)

Cytogenetic and morphological studies were carried out on nine local p opulations of Astyanax scabripinnis paranae. All populations exhibited 2n = 50 chromosomes as well as conspicuous differences involving kary otype morphology, number and position of nucleolar organizer regions ( NORs) and amount and/or locations of constitutive heterochromatin bloc ks. A quantitative study of the cytogenetic data showed that eight pop ulations possessed different karyotypes. Morphological analyses based on nine measurements and two meristic parameters were effective in est ablishing clear identification of five populations. Comparative analys is of cytogenetic and morphological traits suggests that chromosomal c hanges have occurred at a more rapid rate than morphological different iation. Despite the close morphological similarity found among some po pulations, chromosomal differentiation was identified in all of them, even in those presenting only small morphological differences.