A citogenética de Astyanax Lacustris (Lütken, 1875) da Lagoa da Prata - Parnaíba, PI, Brasil

Abstract

Astyanax lacustris (Characidae) is widely distributed in South American river basins and belongs to the Astyanax bimaculatus complex, characterized by the presence of a humeral spot. This study aimed to cytogenetically characterize a population of Astyanax lacustris from Lagoa da Prata, located in the municipality of Parnaíba, Piauí, Brazil, focusing on the determination of diploid number, nucleolus organizer regions (AgNORs) pattern. The analyses revealed a consistent diploid number of 2n = 50 chromosomes in all specimens, with no differences between sexes, indicating chromosomal stability within the population. Silver nitrate staining revealed the presence of multiple AgNOR sites, in contrast to the simple patterns previously described in populations from other regions of Brazil. This polymorphism may be associated with distinct selective pressures imposed by the semi-arid environmental conditions of the Northeast region, suggesting adaptive variations and possible genomic plasticity. The findings contribute to the understanding of chromosomal diversity in A. lacustris, highlighting the importance of regional cytogenetic studies to better comprehend the genetic structure and evolutionary dynamics of Neotropical fish species.