Distribution and status
Arctic to Bristol Channel and Massachusetts.( GBIF map). Common and widespread in northern Britain. Records south of Bristol Channel are probably misidentifications of Onchidoris muricata. (UK interactive distribution map. NBN.)
Ecology and behaviour
On lower shore and sublittorally to 60m. Feeds on wide variety of polyzoans, including Electra pilosa [EML] (often on Fucus serratus), Membranipora membranacea [EML] (often on Laminaria), Flustrellidra hispida [MeL] and Alcyonidium polyoum. Simultaneous hermaphrodite. Cream coloured spiral ribbon of spawn laid February to May. Adults die after spawning so inconspuous until next generation grows. Veliger larvae before transforming into adult form.
Key identification features
- Club-shape or ellipsoid tubercles on mantle have obtusely pointed apex .
- Maximum length usually 17mm.
- Usual maximum of lamellae on rhinophore is 18.
- Usually yellow (EML) in S. Britain, white  in far north, but can vary.
References and links
Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.
Thompson, T.E. & Brown, G.H. 1984. Biology of opisthobranch molluscs 2. London, Ray Society.
Current taxonomy: World Register of Marine Species (WoRMS)
Irish distribution map and prey organisms:
Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML).