''Arctonoe vittata'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of scaled

polychaete Polychaeta () is a paraphyletic class of generally marine Annelid, annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called c ...

worms commonly known as a "scale worm". This species often lives as a

commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit f ...

of another marine animal.

Description

At least thirty pairs of

elytra An elytron (; ; : elytra, ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometime ...

, scale-like modifications to the dorsal cirri, conceal the animal's body. These are on alternate segments and do not meet dorsally, leaving the central line of the body uncovered. ''A. vittata'' is a pale yellowish colour, with a few faint transverse bands, and a dark stripe located across segments 7 and 8. It can grow to a length of but is usually shorter. It can be distinguished from the otherwise similar '' Arctonoe pulchra'' by the absence of a dark spot on each scale.

Distribution

''A. vittata'' is native to the eastern Pacific Ocean. Its range extends from the

Bering Strait The Bering Strait ( , ; ) is a strait between the Pacific and Arctic oceans, separating the Chukchi Peninsula of the Russian Far East from the Seward Peninsula of Alaska. The present Russia–United States maritime boundary is at 168° 58' ...

to Ecuador, and as far west as Japan. Its depth range is from the middle shore down to about .

Ecology

The species forms a commensal relationship with the gumboot chiton, living on its gills and pallial groove. It also lives in the ambulacral groove of '' Dermasterias imbricata'', a starfish. Another host is the keyhole limpet ''

Diodora aspera ''Diodora aspera'', also known as the rough keyhole limpet, is a species of sea snail, a marine gastropod mollusk in the family (biology), family Fissurellidae, the keyhole limpets. Although similar in appearance to a common limpet, it has a hol ...

'' where it lives in the gill groove. It can be very large in comparison with the size of this particular host. If the limpet is attacked by a starfish, such as ''

Pisaster ochraceus ''Pisaster ochraceus'', generally known as the purple sea star, ochre sea star, or ochre starfish, is a common seastar found among the waters of the Pacific Ocean. Identified as a keystone species, ''P. ochraceus'' is considered an important ind ...

'', the scale worm defends its host by biting the tube feet of the starfish, usually succeeding in driving it away. Some other hosts have also been identified; these include the starfishes '' Henricia leviuscula'', '' Luidia foliata'', ''

Pteraster tesselatus ''Pteraster tesselatus'', the slime star or cushion star, is a species of starfish in the family Pterasteridae found in the North Pacific. Description The slime star's body has a wide central disc and five stumpy arms with upturned tips. It gro ...

'', '' Solaster stimpsoni'' and '' Solaster dawsoni'' and the abalone '' Haliotis kamtschatkana'', as well as the terebellid worms '' Thelepus crispus'' and '' Neoamphitrite robusta''. It seems to recognise its host species by some chemical cue in the water; if separated from its symbiont, it attempts to return to its original host or find its way to a new host of the same species. It is carnivorous, but does not feed on its symbiont, preferring to be transported to new feeding grounds and feed on the heads of

tubeworms, or any suitable prey its host may encounter on its travels. It is an efficient walker but a poor swimmer.

References

{{Taxonbar, from=Q2587099 Phyllodocida Animals described in 1855 Annelids of the Pacific Ocean Taxa named by Adolph Eduard Grube