snail GASTROPOD mollusk with a spirally coiled shell; there are thousands of species on land and in water. In aquatic species, respiration is carried on by gills; terrestrial forms often have lungs. Snails secrete a slimy substance over which they move by contractions of their muscular foot. Many species are eaten.
Snails eat mostly plants. Sometimes they eat dead animals. Fish and some birds eat snails. Snails cannot live in water that has a low ph, because their shells will be dissolved.
