Abstract
The genus Astyanax is one of the most numerous of the family Characidae, comprising a large number of similar-shaped species, but displaying innumerable karyotypic variations in its chromosome number and/or structure. The literature describes A. fasciatus populations with diploid chromosome numbers varying from 2n = 45 to 2n = 48. In this study, A. fasciatus specimens captured in the Araguari River (Alto Paraná basin) were cytogenetically characterized, revealing a diploid chromosome number of 2n = 46. The nucleolar organizing regions (NORs), detected with silver nitrate staining, showed a multiple system with two pairs of marked chromosomes. These findings are congruent with those of other studies involving populations of the same species.
Highlights
The genus Astyanax is one of the most numerous of the family Characidae, which comprises species with similar shapes, but displays innumerable karyotypic variations in its chromosome number and/or structure
This paper defines the number of chromosomes and localization of the nucleolar organizing regions (NORs) of an Astyanax fasciatus population from the Araguari
One hundred and eleven metaphases were analyzed from 14 specimens of Astyanax fasciatus, which were silver-stained to determine the AgNOR
Summary
The genus Astyanax is one of the most numerous of the family Characidae, which comprises species with similar shapes, but displays innumerable karyotypic variations in its chromosome number and/or structure. In the same River, Heras (1998, apud Néo, 1999) analyzed specimens with diploid numbers varying from 46 to 48 chromosomes. These numbers reveal an interesting feature of the genus Astyanax: the high variability among specimens of the same population. In these studies, the nucleolar organizing regions (Ag-NORs) occur in more than one chromosomal pair, characterizing multiple NORs. This paper defines the number of chromosomes and localization of the NORs of an Astyanax fasciatus population from the Araguari
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