Chromosomal polymorphism in Serrasalmus spilopleura Kner, 1858 (Characidae, Serrasalminae) from Central Amazon Basin

摘要

Cytogenetic studies were performed in Serrasalmus spilopleura, a piranha species, from three sampling sites in the Central Amazon basin: 1. Catalao; 2. Manacapuru, 3. Itacoatiara, All specimens displayed 2n=60 chromosomes and no sexual chromosomal heteromorphism was found. However, by considering the karyotypic formula, three cytotypes were identifyed: cytotype A consisted of 24M+20SM+4ST+12A, and was the most common being found in all three sampling sites; cytotype C consisted of 23M+21SM+4ST+12A, was found only in Catalao and differ from cytotype A by the presence of a heteroziguous inversion in the first chromosome pair and a distal heterocromatinization in the long arm of this same pair, probably caused by the rearrangement or due to a chromosomal adjustment; cytotype D consisted of 24M+20SM+4ST+12A, was found only in Manacapuru and differ from cytoytpe A by a heteroziguous size polymorphism on the second chromosome pair, probably due to a translocation. C-banding revealed the same constitutive heterochromatin pattern for the three cytotypes except for the chromosome pair that underwent pericentric inversion (cytotype Q which possessed different heterochromatic blocks. Analysis in the number of active nucleolar organizing regions (NORs) revealed no differentiation among cytotypes and NOR-bearing chromosomes varied from 10-12 acrocentric chromosomes. [References: 27]