Phenotypic plasticity and karyotype conservation in allopatric populations of Astyanax aff. fasciatus (Teleostei, Characiformes) at the Upper Paraná river basin

Abstract

Pazza R, Argento R.F.M., Mariano I.H.S., Kavalco K.F. 2016. Phenotypic plasticity and karyotype conservation in allopatric populations of Astyanax aff. fasciatus (Teleostei, Characiformes) at the Upper Paran a river basin. -Acta Zoologica (Stockholm) 97: 241-245.Genus Astyanax is known by its wide genetic and morphological diversity. Among the South America's fish, it is one of the most studied groups and with greatest number of characterized population. At the present work, the combined approach of morphological and genetic data analysis was applied. Cytogenetic and morphometric studies were performed in populations of Astyanax aff. fasciatus originating from Parana ıba river and São João river, both from the hydrographic basin of Parana ıba river. Fish originating from a third place at the Mogi-Guac ßu river (Tietê river's basin) and with 2n = 46 chromosomes also went through morphometric analysis. The morphologic data evidenced the populational structuring, following the geographical distribution of the subjects. Cytogenetic data disclosed the same diploid number and karyotype formula for both populations. The other cytogenetic markers comply with the literature. These data show that the two populations of A. aff. fasciatus do not differ among themselves concerning the chromosomal structure, but they structure themselves regarding morphometry. Aspects of evolution of the group are discussed facing this study.