the Legacy continues…………………….
Gregory R. Mann, Ph.D. {ret.}

Naval Shipworm

“Teredo navalis”

There’s something interesting about Naval Shipworms. They are not a worm but a saltwater clam. Naval Shipworms get their name from their long, narrow, cylindrical bodies but the worm resemblance ends there. A closer look at the creature reveals a shell at its front. This shell has 2 halves with a gap in between like a clam shell. In the gap pokes a muscular foot that acts like a suction cup, holding the shell in place while its razor-sharp edges scrape the wood ahead of it. At the top, 2 flesh-toned siphons swish water over massive gills. At the bottom, a slimy, eyeless head resembles a mix of wet lips & diseased intestines. In between, a glistening gunpowder-blue body stretches up to 4 feet long. Instead of eating, bacteria in the creature’s gills helps it suck energy from sulfur. The whole thing is sheathed in a curving tusk-like tube created from the Naval Shipworm’s excretion of calcium carbonate. Naval Shipworms eat sawdust and it’s stomach has a pouch for storing sawdust and a special gland for digesting wood particles. These “termites of the sea” also have an organ full of bacteria that digest wood. The bacteria take nitrogen from the water and convert it to protein for the worm, since wood doesn’t supply protein. The bacteria in return, get nutrients from their host. A Naval Shipworm begins life like most marine invertebrates: as a tiny piece of meat in the plankton soup of the sea.

Naval Shipworms release eggs into the water column. Free-swimming larvae eventually hatch from the eggs. Larvae remain in the water for 2 to 3 weeks before settling on any submerged untreated wood surface, such as pilings, ship planking and tree trunks or branches. Larvae use a small foot to move around on the wood’s surface. Once they find a suitable place, they anchor themselves using thin threads secreted from a gland on the foot. Larvae use their tiny boring shells to drill and burrow into the wood, where they develop into adults. When it finds a piece of wood, the animal goes to work, using its shell to eat its way into the wood. As a Naval Shipworm grows, so does the burrow as the creature’s breathing siphons remain at the surface of the wood. Depending upon the species and the length of their wooden homes, Naval Shipworms can be as short as 6 inches or as long as 6 feet. Once a Naval Shipworm claims a home, its stuck there for life. Even when researchers removed mature worms intact & uninjured, they were unable to dig new burrows. The damage Shipworms cause is legendary. Greek literature from 350 B.C. mentions them and early explorers dreaded them. Naval Shipworms are sometimes called the mollusk with the million-dollar appetite. These creatures are credited with destroying the Hudson River piers in New York City. Researchers estimate that untreated timbers, such as the pier pilings exposed to Hawaii’s ocean waters will last less than 2 years. In recent history, researchers lowered wooden panels about 5,500 feet to the ocean floor. When they recovered the panels 104 days later, they were completely riddled with the wood-eating Naval Shipworms. This voracious appetite has a purpose. Large amounts of wood get into the oceans by means of rivers, mangrove forests & humans. Naval Shipworms play an important role in reducing the amount of driftwood in the world’s oceans. Shipworms feed mainly on wood, but may also eat planktonic particles brought in through the incurrent siphon.