Cuthona concinna

(Alder & Hancock, 1843)

This rare aeolidacean is inconspicuous, rarely exceeding 12 mm in length in the North Sea. The body is translucent white with chalk-white tips to the tentacles. The cerata are numerous, set in up to ten rows, with up to five cerata per row. The digestive gland lobules within the cerata are usually dull brown in colour, sometimes with a violet tinge, and dark granules within. The ceratal apices are coated with white granules. Some white pigment may also be present around the small cnidosac, and may also form an indistinct streak running down the front of the ceras.

Atlantic specimens feed upon the hydroids Laomedea gelatinosa , Obelia longissima , Sertularia cupressina and S. argentea .

This boreo-arctic species extends from Normandy in France to Finmarken in Norway, including localities all around the British Isles and along the Dutch coast (Distr. C. concinna). American localities include the coast of New England and Vancouver Island.