Teredo navalis
ORDER
Myoida
FAMILY
Teredinidae
TAXONOMY
Teredo navalis Linnaeus, 1758, The Netherlands.
OTHER COMMON NAMES
English: Gribble, pileworm, ship's worm; French: Taret commun; German: Schiffsbohrwurm.
PHYSICAL CHARACTERISTICS
Shell is white, triangular in shape, inflated, and coarsely sculptured with ridges used for burrowing; reduced in size and permanently gaping. It covers only the anterior end of a much larger worm-like soft body. Generally 4 in (10 cm) in total length, but may grow as long as 2 ft (60 cm). Mantle secretes a calcareous lining for wood burrow. The posterior end has short siphons and unsegmented shovel-shaped calcareous pallets used to close the burrow. Stomach has a wood-storing caecum or blind pouch.
DISTRIBUTION
Worldwide in temperate seas, spread by wooden vessels and ballast water. Probably native to northeastern Atlantic; definitely introduced to San Francisco Bay, but additional differentiation of native versus introduced range is unclear. Reported from such far-flung locations as southern Brazil, Zaire, South Australia, the Black Sea, New England, and British Columbia.
HABITAT
Burrows into floating or stationary untreated wood in seawater. Tolerates salinities ranging from normal seawater to 4 ppt.
BEHAVIOR
Specialized for boring in wood by using ridged shell valves to rasp into wood surface. During burrowing, the animal's disk-like foot acts as suction cup to hold shell tightly against end of burrow. When disturbed, it withdraws into burrow and seals opening with specially shaped pallets.
FEEDING ECOLOGY AND DIET
Specialized for boring into and digesting wood with the assistance of symbiotic cellulolytic bacteria and specialized wood-storing caecum on stomach. Ctenidia are well-developed and equipped with food groove, indicating retained ability to filter-feed.
REPRODUCTIVE BIOLOGY
Protandric hermaphrodite. Extended excurrent siphon probably (as known in other Teredinidae) used as copulatory organ for sperm transfer to adjacent individual. Larvae are brooded in gills to veliger stage. Juveniles grow to maturity in eight weeks. Several generations produced per year. Capable of invading new wood only at time of larval settlement.
CONSERVATION STATUS
Not listed by the IUCN. Considered a nuisance species due to wood-destroying capabilities.
SIGNIFICANCE TO HUMANS
Called "termites of the sea." Damage to wooden ships and piers, especially in warm tropical waters, recorded as early as Roman times (A.D. 2). Countered by coating wooden surfaces with tar and pitch in the fifteenth and sixteenth centuries, later by copper plating. Responsible for more than $900 million in damages to wooden piers and quays in San Francisco, California, between 1819 and 1821.
