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

The existence of reproductive isolation between two morphs of catfish, ende mic to the Iguacu River (Brazil), was examined by enzyme starch gel electro phoresis. Tissues of 19 catfish (Pimelodus ortmanni) and 15 of a similar mo rph (Pitnelodus sp.), which differs from P. ortmanni by presenting larger a nd more scattered dusky spots on its skin, were analyzed. A Nei's (1978) ge netic identity of 0.551 was determined by the analysis of 22 enzyme loci. T he loci EST*1, EST*2, GDH*1, GPI*1, GPI*2, IDH*1, MDH*1, MDH*2, and PGM*1 w ere fixed for different alleles in each morph, that is, no heterozygote was found for these loci. The enzymatic patterns observed for the two morphs i ndicate both that the taxa are reproductively isolated and that they in fac t represent separate species.