Genetic evidence for two species of the genus Pimelodus Lacépède, 1803 (Siluriformes, Pimelodidae) in the Iguaçu River (Brazil)

Abstract

The existence of reproductive isolation between two morphs of catfish, endemic to the Iguaçu River (Brazil), was examined by enzyme starch gel electrophoresis. Tissues of 19 catfish (Pimelodus ortmanni) and 15 of a similar morph (Pimelodus sp.), which differs from P. ortmanni by presenting larger and more scattered dusky spots on its skin, were analyzed. A Nei's (1978) genetic identity of 0.551 was determined by the analysis of 22 enzyme loci. The loci EST*1, EST*2, GDH*1, GPI*1, GPI*2, IDH*1, MDH*1, MDH*2, and PGM*1 were fixed for different alleles in each morph, that is, no heterozygote was found for these loci. The enzymatic patterns observed for the two morphs indicate both that the taxa are reproductively isolated and that they in fact represent separate species.<br>Eletroforese de enzimas em gel de amido foi utilizada para verificar a existência de isolamento reprodutivo entre duas formas de mandi endêmicas do Rio Iguaçu (Brasil). Foram analisados tecidos de 19 mandis (Pimelodus ortmanni) e 15 de uma forma semelhante (Pimelodus sp.), que difere de P. ortmanni por apresentar manchas escuras maiores e mais espaçadas sobre a pele. A análise de 22 locos enzimáticos exibiram uma identidade genética de 0,551. Os locos EST*1, EST*2, GDH*1, GPI*1, GPI*2, IDH*1, MDH*1, MDH*2 e PGM*1 se mostraram fixos para alelos alternativos em cada forma, isto é, nenhum heterozigoto para estes locos foi encontrado. Os padrões enzimáticos das duas formas indicaram que elas são reprodutivamente isoladas e que elas representam, de fato, duas espécies separadas

Genetic variability in Astyanax altiparanae Garutti & Britski, 2000 (Teleostei, Characidae) from the Upper Paraná River basin, Brazil

“…The A. altiparanae phenotypes we obtained for the 13 enzymatic systems studied were similar to those previously demonstrated for other Characiformes from the PR basin (Revaldaves et al, 1997;Renesto et al, 1997Renesto et al, , 2001Chiari and Sodré, 1999;Peres et al, 2002) and for Siluriformes (Almeida and Sodré, 1998;Zawadzki et al, 1999Zawadzki et al, , 2000aZawadzki et al, , 2000bRenesto et al, 2000). Our data revealed that A. altiparanae carries high genetic variability, 52.38% of polymorphic loci in PR and 38.10% in the RF.…”

“…Low estimated expected heterozygosity has also been reported for two other Iguaçu River fish, 0. 063 for Crenicichla iguassuensis (Renesto et al, 2001) and 0.024 for Pimelodus ortmanni (Renesto et al, 2000). These low expected heterozygosity values for Iguaçu River species may be due to regulation of invariable structural genes which guarantee phenotypic plasticity (Chippari-Gomes et al, 2003).…”

Comparative application of direct sequencing, PCR-RFLP, and cytogenetic markers in the genetic characterization of Pimelodus (Siluriformes: Pimelodidae) species: Possible implications for fish conservation

“…This is particularly true for species from Neotropical regions. The majority of molecular studies available for the genus Pimelodus use isozymes (Renesto et al, 2000) and random amplification of polymorphic DNA (RAPD) markers (Almeida et al, 2003) to differentiate distinct species within this genus. Only recently, P. albicans was the focus of studies involving the sequencing of mitochondrial genes, which revealed a remarkable haplotype diversity among the samples analyzed and confirmed the occurrence of a species complex (Vergara et al, 2008).…”

“…This genus is apparently paraphyletic, being restricted to South America and characterized by a complex taxonomy (Lundberg and Littmann, 2003). Among pimelodids, Pimelodus is the most genetically studied genus (Renesto et al, 2000;. Because several populations present quite similar morphological traits but distinctive genetic features, some species are commonly known as species complexes, like P. maculatus (Almeida et al, 2003) and P. albicans (Vergara et al, 2008).…”

Cytotaxonomic and evolutionary considerations about karyotipic data of fishes from the Iguaçu River Basin in South of Brazil

“…Garavello and Shibatta (1995) registered a new species using morphological features (Pimelodus sp.). Isoenzyme (Renesto et al, 2000) and chromosomal (Borin and Martins-Santos, 2004) data corroborated that it was really a new species. According to Borin and Martins-Santos (2004), Pimelodus sp.…”