Janolus cristatus

(delle Chiaje, 1841)

This arminacean may reach 75 mm in length; it is oval in outline and resembles an aeolidacean in general appearance, with conspicuous lateral cerata. The body is pale brown or cream in colour, with slightly darker rhinophores and median sensory caruncle. The cerata are numerous, finger-like, inflated and smooth. They are transparent, so that the central brown digestive gland lobe can be seen, running up the centre of each ceras and dividing at the tip. The tips of these cerata are peppered externally with white guanine pigment and have a bluish iridescent quality. Similar white pigment forms a line or blotches down the bare central dorsum, on the metapodium and on and around the lamellate rhinophores (J. cristatus). The bases of the rhinophores are united by a swollen wrinkled accessory caruncle. The anal papilla is postero-dorsal. The head bears short oral tentacles (J. cristatus-detail).

This large species feeds upon erect bryozoa, such as Bugula turbinata , B. plumosa and possibly Cellaria ssp. It is exclusively sublittoral, restricted to hard substrata under clean, calm water. The maximal recorded depth is 40 m.

It has been reported from Norway, the British isles, the French Atlantic coast (as far south as Morocco) and the Mediterranean Sea (to the Bay of Naples) (Distr. J. cristatus).