gastropod

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gastropod,

member of the class Gastropoda, the largest and most successful class of mollusks (phylum MolluscaMollusca
, taxonomic name for the one of the largest phyla of invertebrate animals (Arthropoda is the largest) comprising more than 50,000 living mollusk species and about 35,000 fossil species dating back to the Cambrian period.
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), containing over 35,000 living species and 15,000 fossil forms. The shell of gastropods is of one piece (called univalve) and usually coiled or spiraled as in snailssnail,
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.
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, periwinklesperiwinkle,
any of a group of marine gastropod mollusks having conical, spiral shells. Periwinkles feed on algae and seaweed. They are found at the water's edge; out of water, they resist drying by closing themselves into the shell with a horny plate.
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, conchesconch
, common name for certain marine gastropod mollusks having a heavy, spiral shell, the whorls of which overlap each other. In conchs the characteristic gastropod foot is reduced in size and the operculum, a horny plate located on the foot and used to seal the shell opening
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, whelkswhelk,
large marine gastropod snail found in temperate waters. The whelk is sometimes eaten, but when food is plentiful, fishermen frequently use it for bait. Whelks are scavengers and carnivores, equipped with an extensible proboscis, tipped with a filelike radula, with which
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, limpetslimpet,
marine gastropod mollusk with a simple, flattened, conical shell, found in cooler waters of the Atlantic and the Pacific oceans. Certain species creep over rocks, feeding on algae during high tides, but when the tide recedes they return instinctively to the same spot
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, and abalonesabalone
, popular name in the United States for a univalve gastropod mollusk of the genus Haliotis, members of which are also called ear shells, or sea ears, as their shape resembles the human ear.
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; however, in some forms, as in slugsslug,
name for a terrestrial gastropod mollusk in which the characteristic molluscan shell is reduced to a thin plate embedded in the tissues. Like the terrestrial snails of the same order, slugs have a distinct head with a mouth, tentacles bearing eyes, and a lung for breathing
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 and sea slugssea slug,
name for a marine gastropod mollusk that lacks a shell as an adult and is usually brightly colored. Sea slugs, or nudibranchs, are distributed throughout the world, with the greatest numbers and the largest kinds found in tropical waters.
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, it is reduced or completely absent. There is usually a definite head, bearing one or two sensory tentacles and a mouth that is often equipped with a rasplike tongue called a radula. The lower surface of the animal is modified into a large, flattened foot, used by bottom-dwelling forms for creeping about. The foot and other soft parts of the body can usually be completely withdrawn into the shell and the opening covered by a permanent plate called the operculum. Ancient gastropods were probably bilaterally symmetrical, but living species undergo a process known as torsion in which most of the body behind the head rotates 180° so that the anal and urinary openings are relocated behind the head, and the digestive tract and nervous system become U-shaped. Most gastropod species are marine but many groups, notably the pulmonate (lung-bearing) snails, have successfully invaded freshwater and moist terrestrial habitats.

gastropod

, gasteropod
any mollusc of the class Gastropoda, typically having a flattened muscular foot for locomotion and a head that bears stalked eyes. The class includes the snails, whelks, limpets, and slugs