CYTOLOGIA
Online ISSN : 1348-7019
Print ISSN : 0011-4545
Cytogenetic Diversity in the Astyanax scabripinnis Species Complex (Pisces, Characidae)
I. Allopatric distribution in a small stream
I. L. SouzaO. Moreira-Filho
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JOURNAL FREE ACCESS

1995 Volume 60 Issue 1 Pages 1-11

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Abstract

Cytogenetic investigations were carried out on two populations of Astyanax scabripinnis (Pisces, Characidae, Tetragonopterinae) allopatrically distributed at different altitudes in a stream called Piracuama (Paraíba do Sul Basin, Brazil). Specimens collected at 1800m altitude revealed a diploid number of 2n=50 and a karyotype consisting of 6M+24SM+6ST+14A, with a fundamental number of FN=86. In one of the individuals from this location, we detected the presence of a B-macrochromosome (approximately 8.5% of the haploid complement) similar to those of the first pair in the complement and C positive banding in all extention. The specimens collected from the population located at 780m in the same stream also presented 2n=50, but a karyotype consisting of 4M+10SM+6ST+30A characterized by FN=70. The number of chromosomes bearing nucleolar organizer regions (NORs) also proved to be a differentiation factor at the level of cytogenetic analysis between the specimens of the two populations studied. The distribution of few heterochromatin spots in the chromosomes was a characteristic of both populations. A brief review about the chromosome information currently available about the A. scabripinnis complex is also presented and the possible evolutionary mechanisms involved in the great diversity and speciation of this complex are discussed.

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© The Japan Mendel Society
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