Ship Worm, Or Pile Worm, the popular name of the bivalve shells of the family pholadidoe and genus teredo (Linn.), so called from their perforating ship and other timber. The shell is thick, short, globular, equal-valved, widely open in front and behind, lodged at the larger or inner extremity of a cylindrical tube, straight or sinuous, partly or entirely lined with white calcareous matter, and often open at both ends. The valves are reduced to mere appendages of the foot; in the centre of their circular opening this organ is protruded, the whole forming a very effectual boring apparatus, which is indicated by their peculiar shape, strength, arrangement of the valvular ridges, and great size of the adductor muscle. The animal is elongated and worm-like, the length being due chiefly to the prolongation backward of each respiratory tube, the siphons of which are provided with two calcareous triangular flattened plates, the palettes, which are always turned to the external aperture. The best known species is the teredo navalis (Linn.), whose calcareous tubes are from 1 to 2 1/2 ft. long.
They attack wood immersed in sea water, boring in the direction of the grain, and turning out only for a hard knot, or a companion whose presence they detect by the sense of hearing; the dust of the rasped wood is introduced by the foot into the cavity of the mantle and swallowed, and is usually found filling the long intestine. They are ovovivip-arous, and the young after leaving the body of the mother have a smooth bivalve shell, swim by means of long vibratile cilia, and creep by the tongue-shaped foot; they soon attach themselves to wood and begin to bore, secreting the calcareous tube as they go along; they grow in the wood and enter it when young, as is evident from the external aperture being too small to admit the body of the enclosed adult. From the tropical seas they have been introduced into the temperate waters of Europe and America, and in many places have been exceedingly destructive. The best protection has been found to be metal sheathing and broad-headed nails; and in some cases kyanizing or otherwise poisoning the timber has prevented their attacks.
Other species have been found whose tubes extend from 3 to 6 ft., with walls 1/3 to 1/2 in. thick, and sometimes diverging into two; one burrows in the husks of cocoanuts and other woody tropical fruits floating on the ocean, making very crooked channels. For details see the abstract of a paper read before the national institute at Washington, D. C., by James Jarvis, giving the results of his experiments since 1849 on various kinds of timber, in the "Annual of Scientific Discovery" for 1857, p. 359. - Another pile or timber worm is a minute sessile-eyed crustacean, of the order isopoda, and genus limnoria (Leach). The best known species is the L. terebrans (Leach), 1/5 to 1/3 in. long, rounded at each end, with sides parallel; there are 14 segments, the last two much the largest, the seven next to the head each bearing a pair of short legs; there are two pairs of jaws and a pair of strong mandibles, which are the boring organs; the general color is olive-gray. It can swim as well as creep. All wooden structures immersed in salt water are attacked by it, especially sea bulwarks, and the piles and piers of bridges, docks, and canals; it rarely perforates floating wood.
The perforations are generally for a few feet below low-water mark, and in preference in the direction of the grain between the annual rings; and their numbers are so great that by the time one has perforated an inch the timber is riddled. They are common on both sides of the Atlantic, and are everywhere destructive. They may be guarded against in the same manner as the teredo. These creatures have their uses in disintegrating sunken vessels and substances which would obstruct navigable channels.
Ship Worm (Teredo navalis).
Wood Perforated by Ship Worm.