''Arctonoe vittata'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of scaled

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

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 fro ...

of another marine animal.

Description

At least thirty pairs of

elytra An elytron (; ; , ) 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 (sometimes alterna ...

, scale-like modifications to the dorsal

cirri Giovanni Battista Cirri (1 October 1724 – 11 June 1808) was an Italian cellist and composer in the 18th century. Biography Cirri was born in Forlì in the Emilia-Romagna Region of Italy. He had his first musical training with his brother ...

, 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 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. It also lives in the

ambulacral groove Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include ossicles, plates, spines, and suckers. For example, sea ...

of ''

Dermasterias imbricata The leather star (''Dermasterias imbricata'') is a sea star in the family Asteropseidae found at depths to off the western seaboard of North America. It was first described to science by Adolph Eduard Grube in 1857. Description The leather st ...

'', 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 indi ...

'', 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 ''Henricia leviuscula'', commonly called the Pacific blood star, it is a species of sea star found along the Pacific coast of North America. Description They can usually be identified by their bright orange-red color, but there can also be man ...

'', '' Luidia foliata'', ''

Pteraster tesselatus ''Pteraster tesselatus'', the slime star or cushion star, is a species of starfish in the family (biology), family Pterasteridae found in the Pacific Ocean, North Pacific. Description The slime star's body has a wide central disc and five stump ...

'', ''

Solaster stimpsoni ''Solaster stimpsoni'', common names Stimpson's sun star, sun star, orange sun star, striped sunstar, and sun sea star, is a species of starfish in the family Solasteridae. Description ''Solaster stimpsoni'' is a large species, growing up to 5 ...

'' and ''

Solaster dawsoni ''Solaster dawsoni'', the morning sun star, is a species of starfish in the family Solasteridae. It is found on either side of the northern Pacific Ocean. It has two subspecies: *''S. d. arcticus'' Verrill, 1914 *''S. d. dawsoni'' Verrill, 1880 ...

'' 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 Fauna of the Pacific Ocean Taxa named by Adolph Eduard Grube