B chromosomes in a population of Astyanax eigenmanniorum (Characiformes, Characidae) from the Araguari River Basin (Uberlândia, MG, Brazil)

AUTOR(ES)

Torres-Mariano, Alessandra Ribeiro, Morelli, Sandra

FONTE

Genetics and Molecular Biology

DATA DE PUBLICAÇÃO

2008

RESUMO

A cytogenetic study was conducted on an Astyanax eigenmanniorum population from the Caetano Stream (18° 44' 56" S/ 048° 18' 39" W) - in Uberlândia, MG, Brazil - showing a modal diploid number of 48 chromosomes in the standard male and female karyotypes. However, in several specimens it was also possible to observe metaphases with one or two B chromosomes, increasing the diploid number to 49 or 50 chromosomes, respectively. The supernumerary chromosomes were totally heterochromatic and highlighted after C-banding. The silver-stained nucleolus organizing regions (Ag-NORs) were located in at least five chromosomes of the standard karyotype, thus characterizing a multiple NOR system in the species. This is the first occurrence of an A. eigenmanniorum population with 2n = 48 chromosomes, bearing supernumerary chromosomes.

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