shipworm

/ship"werrm'/, n.

any of various wormlike marine bivalve mollusks that burrow into the timbers of ships, wharves, etc.

[1770-80; SHIP + WORM]

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or pileworm

Any of approximately 65 species (family Teredidae) of common marine bivalves that can severely damage wooden structures, including ship hulls and wharves.

Its anterior end is covered by a shell; the rest is a tubelike structure, sometimes up to 6 ft (1.8 m) long. File-like ridges on its white shell cut into wood at 8–12 rasping motions a minute. It secretes lime to line its burrow, and its tubelike portion extends back to the burrow opening. It ingests food particles and oxygen from the water; some wood is also ingested as food.

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▪ mollusk

also called  pileworm 

 any of the approximately 65 species of marine bivalve mollusks of the family Teredidae (Teredinidae). Shipworms are common in most oceans and seas and are important because of the destruction they cause in wooden ship hulls, wharves, and other submerged wooden structures.

      Only a small part of the anterior end of the shipworm is covered by a shell; the remainder is a long tubelike structure that, in some species, may be 180 cm (6 feet) long. The white shell, often marked with closely set lines, is used for burrowing into wood. File-like ridges on the shell cut into the wood at a rate of about 8 to 12 rasping motions a minute. Shipworms secrete lime to line the inside of the burrow. The tubelike portion of the animal, which extends back to the burrow opening, ingests food particles and oxygen from the water and discharges wastes and reproductive cells. A certain amount of wood is also ingested as food by most species.

      The most economically important shipworms, i.e., those causing the most damage, are members of the genus Teredo, which includes about 15 species. Other genera are Bankia, Xylotrya, and Xylophaga. Teredo norvegica, of the coasts of Europe, has a tube about 30 cm (1 foot) long. The common shipworm, T. navalis (20 to 45 cm [8 to 18 inches] long), has a worldwide distribution but is especially destructive on the Baltic Sea coast.

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