Observations on the life history and geographic range of the giant chemosymbiotic shipworm Kuphus polythalamius (Bivalvia: Teredinidae)

Kuphus polythalamius (Teredinidae) is one of the world’s largest, most rarely observed, and least understood bivalves. Kuphus polythalamius is also among the few shallow-water marine species and the only teredinid species determined to harbor sulfur-oxidizing chemoautotrophic (thioautotrophic) symbionts. Until the recent discovery of living specimens in the Philippines, this species was known only from calcareous hard parts, fossils, and the preserved soft tissues of a single large specimen. As a result, the anatomy, biology, life history, and geographic range of K. polythalamius remain obscure. Here we report the collection and description of the smallest living specimens of K. polythalamius yet discovered and confirm the species identity of these individuals by using sequences of three genetic markers. Unlike previously collected specimens, all of which have been reported to occur in marine sediments, these specimens were observed burrowing in wood, the same substrate utilized by all other members of the family. These observations suggest that K. polythalamius initially settles on wood and subsequently transitions into sediment, where this species may grow to enormous sizes. This discovery led us to search for and find previously unidentified and misidentified wood-boring specimens of this species within museum collections, and it allowed us to show that the recent geographic range (since 1933) of this species extends across a 3000-mile span from the Philippines to Papua New Guinea and the Solomon Islands.