Definitions

shipworm

shipworm

[ship-wurm]
shipworm or teredo, marine bivalve mollusk of the family Teredinidae, specialized for boring in wood. A shipworm is not a worm, but a greatly elongated clam. Its two shells, enclosing only the front end of the body, function as a tool, rather than a protective covering; their ridged and roughened surfaces are used for boring. The burrow (lined with a calcareous coating produced by the clam's mantle) is begun when the animal is in its larval stage and is expanded as it grows. The common shipworm of the North Atlantic Ocean, Teredo navalis, may grow up to 2 ft (60 cm) long, although its shells remain only 1/2 in. (12 mm) long. Shipworms feed on wood particles and minute organisms. They do enormous damage to piers and ships, and although they are deterred by chemicals, control is still a problem. Shipworms are classified in the phylum Mollusca, class Pelecypoda or bivalvia, order Eulamellibranchia, family Teredinidae.
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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Shipworms are not worms at all, but rather a group of unusual saltwater clams with very reduced shells, notorious for boring into (and eventually destroying) wooden structures which are immersed in sea water, including piers, docks and wooden ships. Sometimes called "termites of the sea", they are marine bivalve molluscs (Eulamellibranchiata) in the family Teredinidae, also often known as Teredo Worms.

When boring into submerged wood, bacteria in a special organ called the gland of Deshayes allows them to digest cellulose. The excavated burrow is usually lined with a calcareous tube. Shipworms have slender worm-like forms, but nonetheless possess the characteristic structures of bivalves. The valves of the shell of shipworms are small separate parts located at the anterior end of the worm, used for excavating the burrow.

The shipworms belong to several genera, of which Teredo is the most commonly mentioned. The best known species is Teredo navalis. Historically, Teredo concentrations in the Caribbean Sea have been substantially higher than in most other salt water bodies.

Shipworms greatly damage wooden hulls and marine piling, and have been the subject of much study to find methods to avoid their attacks. These organisms are referenced in the article about copper, for the use of copper sheathing on wooden ships during the Age of Exploration, as a method of preventing damage by "teredo worms". Christopher Columbus's ships were among the earliest known to employ this defense.

Genera within the family Teridinidae

Engineering inspiration

In the early 1800s, the behaviour and anatomy of the shipworm inspired the great British engineer Marc Brunel. Based on his observations of how the shipworm's valves simultaneously enable it to tunnel through wood and protect it from being crushed by the swelling timber, Brunel designed an ingenious modular iron tunnelling framework - a tunnelling shield - which enabled workers to successfully tunnel through the highly unstable river bed beneath the Thames. The Thames Tunnel was the first successful large tunnel ever built under a navigable river.

References

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