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Teredo navalis : ウィキペディア英語版 | Teredo navalis
''Teredo navalis'', the naval shipworm, is a species of saltwater clam, a marine bivalve mollusc in the family ''Teredinidae'', the shipworms. This species is the type species of the genus ''Teredo''. Like other species in this family, this bivalve is called a shipworm, because it resembles a worm in general appearance, while at the anterior end it has a small shell of two valves which is specialised to bore through wood. This species may have originated in the northeast Atlantic Ocean, but has spread around the world. It tunnels into underwater piers and pilings and is a major cause of damage and destruction to submarine timber structures and the hulls of wooden boats. ==Description== ''Teredo navalis'' has an elongated, reddish, wormlike body which is completely enclosed in a tunnel it has made in floating or submerged timber. At the front end of the animal are two triangular, calcareous plates. These are up to long and correspond to the valves of other bivalve molluscs. They are white, with a covering of pale brown periostracum, and have rough ridges. The mollusc uses them to rasp the wood and slowly enlarges the burrow in which it lives. It has retractable inhalant and exhalant siphons which project through a small hole in the horny septum which blocks the opening of the burrow. When the animal is threatened, the siphons can be drawn inside the burrow and protected by a pair of calcareous oar-like pallets. The tunnel is circular in cross section and is lined with calcareous material extruded by the mollusc. It can be up to long and in diameter.〔(''Teredo navalis'' Linnaeus, 1758 – Naval shipworm ) SeaLifeBase. Retrieved 2012-04-13.〕〔(''Teredo navalis'' – Naval Shipworm ) Smithsonian Marine Station at Fort Pierce. Retrieved 2012-04-13.〕
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