Acanthodoris pilosa

(Abildgaard in Müller, 1789)

This common species may reach 55 mm in length, although it does not usually exceed 40 mm. The colour varies from white or yellow through pale grey or brown to dark purplish brown or charcoal grey. Although speckled juveniles have been recorded. The dorsal surface of the ample mantle is covered by soft, tall, conical tubercles. The rhinophores are clubbed and bent rearwards; in a 10 mm specimen there were seventeen lamellae on each tentacle, in a 30 rim specimen 23 or 24. The rhinophores issue from low pallial sheaths which have crenulated rims. There are up to nine voluminous tripinnate gills. Blunt, rounded oral tentacles are present (Acanthodoris pilosa); (A. pilosa-eggs).

This species feeds upon encrusting polyzoans, especially Flustrellidra hispida and species of Alcyonidium. It is found in very shallow water and on the lower shore.

It has been recorded from the Arctic Ocean to the Mediterranean Sea (Sicily) and both seaboards of the USA, to 170 m; common on both coasts of the North Sea (Distr. A. pilosa).