Why shipworms bore into submerged wood

A clam with an unexpected shape

Harvard’s museum account describes the naval shipworm, Teredo navalis, as a bivalve: the same broad mollusc group as clams and mussels. Its small shell sits at the front of a long body. Instead of enclosing that body in a large protective shell, the animal occupies a burrow in wood. The name can therefore mislead twice: it is not a worm, and wooden ships are not its only home.

The shell does the scraping

The hard shell surfaces work against the timber, producing particles the animal can ingest. Northeastern’s account of its researchers’ work explains the connection between this mechanical action and the enzymes involved in digestion. Boring and digesting are different parts of the process: making a tunnel alone does not explain how the animal gains nourishment from difficult-to-break-down wood.

The biology is more interesting than a nickname

In 2022, Northeastern researchers described a route by which digestive enzymes travel from the gill region towards the digestive tract through tiny ducts. NSF’s report on separate research in 2024 describes bacteria found in an overlooked digestive structure, the typhlosole. These accounts concern particular investigations; they should not be flattened into a claim that every shipworm species has an identical digestive system.

The useful distinction is between observing the burrow and explaining the living partnership. The holes are visible evidence of activity. The distribution of microbes and the movement of enzymes require laboratory investigation. A beach photograph cannot establish those details.

Read the wood without diagnosing it

The term shipworm covers more than one species. For a curious shore visitor, the burrows offer a way into marine natural history. For someone responsible for a boat, pier or historic wooden structure, the question is different: what is the timber’s actual condition, and what assessment does it need? This article cannot identify an active infestation or determine whether wood is sound. Seek a qualified inspection for those decisions.