Freshwater Pulmonate Gastropods

Freshwater pulmonate snails are characteristically thin and light shelled. Many can regulate their buoyancy to neutral and even positive by taking air into a "lung," which allows them to glide upside down on the air/water surface. Their life cycle is rapid. In nature, one or two generations per year may be produced, with complete replacement of individuals (Brown, 1991). All are hermaphroditic; that is, each individual has the capacity to function as both male and female. Unlike the prosobranchs, with many endemic species and varieties, the pulmonate species are fewer but much more widespread. Freshwater pulmonates reach their greatest size and diversity in the northern latitudes, and many species are commonly found in shifting and ephemeral habitats.

Although all are in the subclass Pulmonata, the freshwater pulmonate snails are not closely related to ...