FRESHWATER SNAIL

any of the approximately 5,000 snail species that live in lakes, ponds, and streams. Most are members of the subclass Pulmonata; some are members of the subclass Prosobranchia; both subclasses belong to the class Gastropoda. The southeastern United States has the greatest number of species; another notable location is Lake Tanganyika, in Africa. Freshwater snails are distributed via birds' feet, wind-blown leaves, and floods. Several species are hosts of flatworms causing disease in warm-blooded animals; e.g., schistosomiasis. Large forms used to keep aquariums clean include the amphibious snail Ampullarius gigas.