Comparação molecular de populações naturais de Jaú (Zungaro) (Pisces, Siluriformes, Pimelodidae) das bacias amazônica e do Paraná-Paraguai.

Abstract

Species of the Zungaro genus, popularly known as jaú , have great economical importance on the fishing industry. They are among the largest migratory fishes in Brazil, occurring throughout the Amazon and Paraná-Paraguay basins. They have usually been relatively abundant in the Paraná-Paraguay River Basin, but after the enclosure of several dams, a considerable decline on population size was recorded. In this study, Zungaro populations of Paraná-Paraguay River and Amazonic basins were molecularly described (variability and genetic structuration) through mitochondrial genome. The analyses of mitochondrial sequences of D-loop and ATPase 6 gene regions evidenced a genetical difference corresponding to intimately related species, as recorded in literature. Therefore, it supports the conclusion that the Zungaro population of the Paraná-Paraguay River basin (Zungaro jahu) does not belong to the same species found in the Amazonic basin (Zungaro zungaro). When molecular analyses of sub-populations of the Paraná-Paraguay basin were made, AMOVA and FST detected the identicalness of both subpopulations, demonstrating that they are not genetically different, i.e., present a very low genetical variability. This fact may be related to the founder or bottleneck effects. As Z. jahu is an endemic species of the Paraná-Paraguay basin, these results indicate that should this species disappear from Paraná River, due to reservoir building, remaining individuals will be located only in Paraguay River, subject to many survival hardships caused by low genetical diversity.