Melanoides tuberculata (Müller, 1774): northeastern dispersal in the São Francisco basin, Brazil

Melanoides tuberculata (Müller, 1774) (Gastropoda: Thiaridae) is the exotic species with the widest distribution among the freshwater macrobenthos in Brazil. The snail is a threat to native species and has medical and economical importance. In this study the occurrence of M. tuberculata is recorded and reported in the São Francisco River Basin, along a border area including three northeastern states of Brazil: Bahia, Sergipe and Alagoas. These data are especially important due to the new watercourses resulting from the integration of the São Francisco River to other regional basins.