Cytogenetic characterization of distinct B chromosomes in a population of the fish Astyanax bockmanni (Teleostei, Characiformes)
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Univ Florence Botany Inst
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Individuals of Astyanax bockmanni from one population belonging to the Paranapanema River basin, southeastern Brazil, were cytogenetically examined. In the present paper, we report a diploid number of 50 chromosomes, with some individuals bearing additional chromosomes, characterized as different variants of B chromosomes. The B microchromosome of acrocentric morphology (B-a) was the most frequent type in this population (77.7%). Two other variants were identified as metacentric B chromosomes, but of distinct sizes, characterized as macrochromosome (B-M) and microchromosome (B-m). Conspicuous heterochromatic blocks were observed in the terminal regions of some chromosomes of the standard karyotype and partially heterochromatic blocks were detected in all B chromosomes. 18S ribosomal RNA genes were distributed in the terminal region of several chromosomes, but were not located on the B chromosomes.
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chromosome polymorphism, fish cytogenetic, in situ hybridization, isochromosome, supernumerary chromosomes
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Inglês
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Caryologia. Florence: Univ Florence Botany Inst, v. 65, n. 3, p. 229-233, 2012.
