snail, name commonly used for a gastropod mollusk with a shell. Included in the thousands of species are terrestrial, freshwater, and marine forms. Some eat both plant and animal matter; others eat only one type of food. Respiration is carried on by gills in the aquatic species; terrestrial forms have a pulmonary sac, or lung, in the mantle cavity. A few terrestrial species have returned to the sea, and consequently must rise to the surface to breathe. Eyes are borne on stalks or tentacles. Many snails, including all land snails, are hermaphroditic, but the majority of the marine species have separate sexes. A snail secretes a slimy path over which it progresses slowly by rhythmic contractions of the muscular base, or foot. Marine and terrestrial snails are eaten in various parts of the world. Snails are considered a delicacy in Europe and were eaten by primitive man and raised for food by the Romans. Certain harmful freshwater species harbor flukes and other parasites that cause disease in humans. Although some land snails cause economic losses by destroying vegetation, even more harm is done to gardens by slugs. Snails are classified in the phylum Mollusca, class Gastropoda.
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