It has a commensal relationship with a hermit crab and occurs on the lower shore of coasts on the western side of the Atlantic Ocean.

Dipolydora commensalis is a burrowing worm that invariably bores into a gastropod mollusc shell that is being used by a hermit crab.

[2] A pair of palps on the prostomium (first segment) catch food particles floating past.

[2] The palps are able to regrow if they are damaged by movements of the hermit crab, and both the anterior and posterior parts of the worm are able to regenerate if it gets severed.

In the laboratory, worms can live for four years, rather longer than most empty gastropod shells.