In some, it is modified for swimming or burrowing. Gastropods are dioecious, and some forms are hermaphroditic. Marine species have veliger larvae. Torsion in gastropods has the unfortunate result that wastes are expelled from the gut and nephridia near the gills. A variety of morphological and physiological adaptations have arisen to separate water used for respiration from water bearing waste products.
Gastropods are by far the largest group of molluscs.
Gastropod feeding habits are extremely varied, although most species make use of a radula in some aspect of their feeding behavior. Some graze, some browse, some feed on plankton, some are scavengers or detritivores, some are active carnivores. Animal Diversity . Brusca, R. C., and G. J. Brusca. The two species of Cipangopaludina were introduced from East Asia, Viviparus georgianus from the southern U.S.A., and Valvata piscinalis, Bythinia tentaculata and Radix auricularia from Europe.