Gastropods and freshwater bivalves from the median region of the Rio Doce basin, Minas Gerais, Brazil

Abstract

A survey of the lymnic malacofauna from the mid-segment of the Rio Doce basin was carried out from 1999 to 2001. The studied region is permanently submitted to the impact of mining, reforestation, urban waste, metallurgy, and includes two areas of high priority preservation. Sixteen sampling station distributed into 6 sub-basins were investigated. Eight thousand four hundred and eleven specimens of mollusks were collected, 6.224 (74%) being gastropods and 2.187 (26%) bivalves. The presence of the following mollusks with their relative frequency, respectively, could be observed: 1) Gastropods: Ancylidae (0.1%), Planorbidae, Biomphalaria (1.4%), Hydrobiidae (2.9%), Thiaridae, Melanoides tuberculatus (59.6%), Physidae, Physa (10%) and specimens of the family Ampullariidae, Pomacea (0.1%); 2) Bivalves: Sphaeriidae (0.5%), Corbiculidae (25.3%), Mycetopodidae (0.1%). It was observed that 84.9% of the collected specimens were Melanoides tuberculatus and Corbicula, both introduced mollusks. The presence of the mollusks detected was connected to the environment of each sampling place.