Esterase-D and chromosome patterns in Central Amazon piranha (Serrasalmus rhombeus Linnaeus, 1766) from Lake Catalão

Abstract

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-D3 11 , Est-D3 12 , Est-D3 22 and Est-D3 33 ) out of six theoretically possible genotypes, presumably encoded by alleles Est-D3 1 (frequency = 0.237), EsT-D3 2 (0.710) and Est-D3 3 (0.053). A Chi-squared (c 2 ) 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-D3 0 ) 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-D3 3 allele. The data as a whole should contribute to the better understanding the rhombeus complex taxonomic status definition in the Central Amazon.

Karyotype differentiation and cytotaxonomic considerations in species of Serrasalmidae (Characiformes) from the Amazon basin

“…rhombeus) bearing 2n = 58 chromosomes (Nakayama et al, 2001), as well as another karyomorph was identified by chromosomal and molecular analyses (Teixeira et al, 2006), suggesting that S. rhombeus is a complex of species. This hypothesis is strengthened by the present data on 18S rDNA sites, since S. cf.…”

Mapping of ribosomal genes and chromosomal markers in three species of the genus Serrasalmus (Characidae, Serrasalminae) from the Amazon basin

“…For instance, four distinct karyotypes were found in S. maculata (junior synonyme -S. spilopleura Jégu and Santos, 2001) in the confluence of the Negro and Solimões Rivers, Amazon Basin (Nakayama et al, 2000;Centofante et al, 2002), while three karyomorphs were reported in the Paraná Basin population (Cestari and Galetti, 1992b). While S. rhombeus presented a karyotype with 2n = 60; a criptic species presented 2n = 58 and a karyotype probably derived from the 2n = 60 by chromosome fusions (Nakayama et al, 2001), and a third new karyomorph was also reported (Teixeira et al, 2006).…”

Comparative cytogenetics of Serrasalmidae (Teleostei: Characiformes): The relationship between chromosomal evolution and molecular phylogenies

“…In Serrasalmus , for example, three karyomorphs of S . rhombeus Linnaeus 1766 occurring in syntopy were found, which varied both in 2n and in the karyotype formula [ 26 , 27 ]. Different karyomorphs were also observed in specimens of S .…”