(Linné, 1761)
Description:
This animal reaches a length of 120 mm. The broad, depressed body bears up to 25 obliquely transverse rows of elongated, somewhat flattened cerata, which leave bare a substantial median zone behind the rhinophore bases. This bare area usually exhibits white pigment in the shape of a diamond or a crescent, often linked to similar pigment streaking the upper surfaces of the oral tentacles. The ground colour of the body is very variable, ranging from pale grey through shades of brown to rich purple-brown, with freckles of white, grey, brown or violet. The cerata are usually white-tipped, as are the rhinophores (A. papillosa-drawing); (A. papillosa-with eggs).
Habitat:
It is a common and successful shallow-water nudibranchs, consuming sea-anemones. Just about any species will be attacked, but Actinia and Metridium seem to be the most important.
Distribution:
Widely distributed from the White Sea to Arcachon and Asturias, from Baffin Land to New England, and from the Falkland Islands, California and Alaska, to 800 m depth (Distr. A. papillosa).