Adyte assimilis is a marine polychaete scale worm in the family Polynoidae

Polynoidae

A family of scaled Polychaete worms known as the "scale worms". Short and flat, specimens reach as much as 20 cm in length and 10 cm width. An almost-constant number of small segments is the norm. They are covered by scales, technically termed elytra....

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Description

A. assimilis is colourless or yellowish, up to thirty millimetres long, and has a dark band running down its back. It has fifteen pairs of scales or elytrae which cover the length of the body. These are delicate, transparent and rounded and do not meet at the back. The body is of uniform width with smooth dorsal and ventral surfaces. The prostomium has a median antenna and a pair of lateral antennae. There are a pair of palps and two pairs of eyes, the anterior pair on the line of greatest width, the posterior pair near the rear margin. The first segment bears chaetae and a pair of dorsal and ventral tentacular cirri. There is a long posterior region without scales. The notosetae are at least as thick as the neurosetae, being smooth with few spines. The neurosetae have semilunar pockets, faintly bifid tips and faint serrations. The presetal neuropodial lobes are longer than the postsetal ones.

Distribution

A. assimilis is found in the Pacific, Indian and Atlantic Ocean, the Mediterranean Sea, the Red Sea and the Bosporus, the English Channel and the North Sea.

Biology

A. assimilis is widely distributed round the shores of Britain where it is found on the lower shore and always in association with the sea urchin, Echinus esculentus, among whose spines it lives. It ranges from the littoral to the sublittoral zones and is often associated with starfish, brittle star

Brittle star

Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...

s and feather stars

Crinoid

Crinoids are marine animals that make up the class Crinoidea of the echinoderms . Crinoidea comes from the Greek word krinon, "a lily", and eidos, "form". They live both in shallow water and in depths as great as 6,000 meters. Sea lilies refer to the crinoids which, in their adult form, are...

. It is an omnivore and both a scavenger and a predator.