Hairy Spiny Dorid

Overview

The Hairy Spiny Dorid (Acanthodoris pilosa) is a distinctive nudibranch easily recognized by its rounded, fluffy appearance. This sea slug is widely distributed across the North Atlantic and parts of the North Pacific, typically inhabiting shallow rocky environments where it feeds on bryozoans.

Appearance

This species is characterized by a soft, oval-shaped body covered in numerous long, fleshy, and pointed papillae, which give it a "fluffy" or "hairy" texture. It possesses two prominent, backward-curving rhinophores at the front and a distinctive ring of up to nine large, feathery gills at the rear. Its coloration is highly variable, ranging from white and cream to shades of brown, purple, or charcoal grey. While adults typically measure around 3 cm in length, they can occasionally reach up to 7 cm. Juveniles often display a speckled pattern, whereas deeper-water individuals tend to be paler in color.

Distribution & habitat

Acanthodoris pilosa is common throughout the British Isles and is found along the coasts of Norway, France, and across the North Atlantic to the eastern shores of Canada and the United States. It also occurs in the North Pacific. It is primarily a shallow-water species, frequently encountered in the intertidal zone and subtidal rocky habitats, though it has been recorded at depths reaching 80 meters.

Feeding

This nudibranch is a specialized predator that feeds on encrusting bryozoans. On the shore, it is commonly found grazing on species such as Alcyonidium hirsutum and Flustrellidra hispida, while in deeper sublittoral waters, it often targets the erect, fleshy bryozoan Alcyonidium diaphanum.