Arctonoe fragilis (Baird, 1863)
Common name(s): Commensal scaleworm, Ruffled scaleworm, Fragile scaleworm, Frilled commensal scaleworm, Scaleworm
|Synonyms: Polynoe fragilis, formerly part of Arctonoe vittata|
|Actonoe fragilis on the ray of its host seastar, Evasterias troschelii.|
|(Photo by: Dave Cowles, July 2005)|
How to Distinguish from Similar Species:Arctonoe pulchra and Arctonoe vittata have elytra whose margins are smooth or only slightly ruffled, plus Arctonoe vittata has a dark band across segments 7 and 8 behind the head.
Geographical Range: Alaska peninsula to San Francisco Bay, CA (uncommon in CA)
Depth Range: Low intertidal to 275 m
Habitat: Mostly symbiotic on the seastar Evasterias troschelii
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.
|Main Page||Alphabetic Index||Systematic Index||Glossary|
Brusca and Brusca, 1978
Morris et al., 1980
O'Clair and O'Clair, 1998
Ricketts et al., 1985
|These two views show Arctonoe fragilis on the ray of Solaster stimpsoni.||Photos by Dave Cowles, July 2005|
This large 7 cm-long individual was commensal on the seastar Orthasterias koehleri. Click Here to see the worm on its host seastar.