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Cytogenetic divergence in two sympatric fish species of the genus Astyanax Baird and Girard, 1854 (Characiformes, Characidae) from northeastern Brazil

Author(s): Aline Souza Medrado | Mavione Souza Ribeiro | Paulo Roberto Antunes de Mello Affonso | Paulo Luíz Souza Carneiro | Marco Antônio Costa

Journal: Genetics and Molecular Biology
ISSN 1415-4757

Volume: 35;
Issue: 4;
Start page: 797;
Date: 2012;
Original page

Keywords: Ag-NOR | cytotaxonomy | fish | fluorochromes | South America

The fish genus Astyanax is widespread throughout the Neotropical region and is one of the most species-rich genera of the Characiformes. Cytogenetic studies of Astyanax have revealed marked intra-and interspecific diversity, with the identification of various species complexes. In this report, we describe the karyotypic structure of two sympatric species of Astyanax (Astyanax sp. and Astyanax aff. fasciatus) from the Middle Contas River basin in the northeastern Brazilian state of Bahia. Both species had 2n = 48 but differed in their karyotypic formulae. Small heterochromatic blocks and multiple nucleolar organizer regions (NORs) were identified in both species. Terminal CMA3+/DAPI-signals were observed in Astyanax sp. and A. aff. fasciatus, mostly coincident with NORs. These results show that chromosomal markers can be used to identify species in this fish complex. These markers can provide useful information for evolutionary studies and investigations on the mechanisms of chromosomal diversity in Astyanax.

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