''Arctonoe'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of worms belonging to the family

Polynoidae Polynoidae is a family of marine Polychaete worms known as "scale worms" due to the scale-like elytra on the dorsal surface. Almost 900 species are currently recognised belonging to 9 subfamilies and 167 genera. They are active hunters, but gene ...

. They are commonly known as "scale worms". Members of this genus predominantly occur in shallow (50 metres or less) waters of the northeast

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

and often live as commensals of other marine invertebrates, frequently echinoderms but sometimes

molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...

or other

polychaetes Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made ...

Description

Arctonoe have long bodies, with 100 or more segments and numerous pairs of smooth translucent scales (

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 ...

) on several of the segments. The first segment (

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; plural: prostomia; sometimes also called the "acron") is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not include) t ...

), which contains the mouth, is rounded and smooth; on its side it has antennae pointing away from the body.

Parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; plural: parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed ...

are found along the body with both dorsal (notopodial) and ventral (neuropodial)

acicula Acicula (singular: aciculum) are strong, stout internal chaetae that provide support to parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; plural: parapodia) refers to lateral outgrowths or protr ...

penetrating epidermis. The

notochaetae A chaeta or cheta (from Greek χαίτη “crest, mane, flowing hair"; plural: chaetae) is a chitinous bristle or seta found in annelid worms, (although the term is also frequently used to describe similar structures in other invertebrates such ...

are few in number and more slender than the

neurochaetae A chaeta or cheta (from Greek χαίτη “crest, mane, flowing hair"; plural: chaetae) is a chitinous bristle or seta found in annelid worms, (although the term is also frequently used to describe similar structures in other invertebrates such ...

both

and

have minutely notched tips (see Hanley, 1989 for detailed diagnosis).

Species

The following species of ''Arctonoe'' are recognised as valid as of June 2020: *'' Arctonoe fragilis'' (Baird, 1863) *'' Arctonoe pulchra'' (Johnson, 1897) *'' Arctonoe vittata'' (Grube, 1855)

References

{{Authority control Polychaete genera Phyllodocida