Genetics and Molecular Biology
On-line version ISSN 1678-4685
TEIXEIRA, Aylton Saturnino; NAKAYAMA, Celeste Mutuko; PORTO, Jorge Ivan Rebelo and FELDBERG, Eliana. Esterase-D and chromosome patterns in Central Amazon piranha (Serrasalmus rhombeus Linnaeus, 1766) from Lake Catalão. Genet. Mol. Biol. [online]. 2006, vol.29, n.3, pp. 498-502. ISSN 1678-4685. http://dx.doi.org/10.1590/S1415-47572006000300018.
This study presents additional genetic data on piranha (Serrasalmus rhombeus Linnaeus, 1766) complex previously diagnosed due to the presence of distinct cytotypes 2n = 58 and 2n = 60. Three esterase-D enzyme loci (Est-D1, Est-D2 and Est-D3) were examined and complemented with chromosomal data from 66 piranha specimens collected from Lake Catalão. For all specimens the Est-D1 and Est-D2 loci were monomorphic. In contrast, the Est-D3 locus was polymorphic with genotypes and alleles being differentially distributed in the previously described cytotypes and served as the basis for detecting a new cytotype (2n = 60 B). In cytotype 2n = 58 the Est-D3 locus was also polymorphic and presented Mendelian allelic segregation with four genotypes (Est-D311, Est-D312, Est-D322 and Est-D333) out of six theoretically possible genotypes, presumably encoded by alleles Est-D31 (frequency = 0.237), EsT-D32 (0.710) and Est-D33 (0.053). A Chi-squared (c2) test for Hardy-Weinberg equilibrium was applied to the Est-D3 locus and revealed a genetic unbalance in cytotype 2n = 58, indicating the probable existence in the surveyed area of different stocks for that karyotypic structure. A silent null allele (Est-D30) with a high frequency (0.959) occurred exclusively in the 2n = 60 cytotype. On the other hand, the new cytotype 2n = 60 B described here for the first time was monomorphic for the presumably fixed Est-D33 allele. The data as a whole should contribute to the better understanding the rhombeus complex taxonomic status definition in the Central Amazon.
Keywords : Brazilian Amazon basin; esterase enzymes; Serrasalmus rhombeus species complex; karyotype.