(Savigny, 1820)
Description:
Body long, tapering posteriorly, integument smooth.
Prostomium with a pair of antennae without cirrophores, a pair of biarticulate palps slightly shorter than the antennae and 2 pairs of eyes in a trapezoid arrangement.
First segment twice as long as the first chaetiger, sometimes appearing inflated; with 4 pairs of tentacular cirri differing little in length; second dorsal tentacular cirrus reaching chaetiger 4.
Pharynx with a pair of denticulate jaws; oral and maxillary rings with prominent conical paragnaths, absent only from group V; group I: (1-2); group II: small patches of 6-10; group III: small patch of 6-10; group IV: patches of 10-15; group VI: patches of 6-12; groups VII-VIII: a row of large paragnaths, with irregular rows of smaller paragnaths towards the mouth.
Parapodia of the first two chaetigers uniramous, with 3 lobes.
Remaining parapodia biramous with 4 lobes. Dorsal notopodial lobe the largest, becoming leaf-like in the mid-body and posterior chaetigers, particularly in large animals. The remaining lobes change little along the body length, notopodial acicular and ventral neuropodial lobes of similar shape, the notopodial acicular being slightly the larger; neuropodial acicular lobe has a sharply tapering tip and is the shortest. The orientation of the parapodium of the posterior chaetigers changes, with the development of the dorsal notopodial lobe. Dorsal cirri always longer than the parapodial lobes, originating about halfway along the dorsal edge of the dorsal notopodial lobe in posterior chaetigers. Ventral cirri shorter than the ventral neuropodial lobe anteriorly, then as long as or longer than it posteriorly (N. fucata-parapodium). Notopodial chaetae homogomph spinigers. Neuropodial chaetae homogomph spinigers and heterogomph falcigers above and heterogomph spinigers and falcigers below the acicula (N. fucata-chaeta).
Size:
Up to 200 mm for 120 segments.
Colour:
Dorsum yellowish with red and white longitudinal bands.
Epitoke:
Body divided into 2 regions, an anterior region of 24 chaetigers in males and 27-29 in females. Modifications of the dorsal or ventral cirri of anterior chaetigers have not been described in males and do not occur in females.
Metamorphosed parapodia from the posterior part of the body develop accessory flaps at the base of the dorsal cirrus, below the notopodial acicular lobe, on the posterior surface of the neuropodial acicular lobe and at the base of the ventral cirrus. The accessory flaps are well developed in both sexes. In males, crenulations develop along the lower edge of the dorsal cirri, but it is not known if a pygidial rosette is present. In both sexes, the ordinary chaetae are replaced by paddle chaetae in modified parapodia, although a few remaining atokous chaetae may be present in females.
Habitat:
Commensal with the hermit crab Pagurus bernhardus , living in gastropod shells. Occasionally, specimens are found not associated with hermit crabs, but this is likely to be only a temporary phenomenon.
Distribution:
North Sea, Kattegat, English Channel, North Atlantic, Black Sea and Mediterranean.