| Shipworm | |
|---|---|
| Teredo sp. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Bivalvia (or Pelecypoda) |
| Order: | Myoida |
| Family: | Teredinidae Rafinesque, 1815 |
| Genera | |
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Shipworms are not worms at all, but rather a group of unusual saltwater clams with very small shells, notorious for boring into (and eventually destroying) wooden structures that are immersed in sea water, such as 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.
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When shipworms bore into submerged wood, bacteria (Teredinibacter turnerae strain ATCC 39867 / T7901) in a special organ called the gland of Deshayes allow them to digest cellulose.[1] 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. Copper sheathing was used on wooden ships in the latter 18th century and afterwards, as a method of preventing damage by "teredo worms". The first historically documented use of copper sheathing were experiments held by the British Royal Navy with HMS Alarm, which was coppered in 1761 and thoroughly inspected after a two year cruise. In a letter from the Navy Board to the Admiralty dated 31 August 1763 it was written "that so long as copper plates can be kept upon the bottom, the planks will be thereby entirely secured from the effects of the worm."
In the Netherlands the shipworm caused a crisis in the 18th century by attacking the timber that faced the sea dikes. After that the dykes had to be faced with stones. Teredo has recently caused several minor collapses along the Hudson River waterfront in Hoboken, New Jersey, due to damage of underwater pilings.[2]
More recently, the endosymbionts that are found in the gills have been subject to study the bioconversion of cellulose for fuel energy research.[3]
In the early 19th century, the behaviour and anatomy of the shipworm inspired the French engineer Marc Brunel, the father of the famous British engineer Isambard 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 tunnel successfully through the highly unstable river bed beneath the Thames. The Thames Tunnel was the first successful large tunnel ever built under a navigable river.[4]
In Palawan and Aklan in the Philippines, the shipworm is called tamilok and is eaten as a delicacy there. It is prepared as kinilaw—that is, raw (cleaned) with vinegar or lime juice, chopped chili peppers and onions, very similar to ceviche. The taste of the flesh has been compared to a wide variety of foods, from milk to oysters.[5]
Genera within the family Teridinidae include: