Biology/Natural History: These worms are most often commensals on painted seastars Evasterias troschelii, but it may sometimes be found on other species of seastar or may be freeliving. Alternate hosts include Leptasterias aequalis, Leptasterias hexactis, Orthasterias koehleri, Stylasterias forreri, Luidia foliata, Pisaster ochraceous, and Solaster dawsoni. They are attracted by the smell of their host, at least as long as the host is uninjured. Usually only one individual occurs on a host at a time (they are antagonistic to one another), but up to 4 have been found. They feed on detritus

Members of Family Polynoidae, unlike most other errant polychaetes, have parapodia specialized for walking rather than as paddles. Their longitudinal muscles, which caused lateral undulations in other polychaetes, are poorly developed and they don't undulate much. As a result, although they can walk efficiently they are poor swimmers.