Up to 60mm long. Ample mantle covers whole body. Sandy-brown [image1], grey-cream, yellow, buff-orange, white (Flickr) or bluish white (Flickr), often with faint freckles like those on a fair skinned human, and often a few dark marks in two or three longitudinal rows. Mantle densely covered with tiny tubercles, barely visible to naked eye; under magnification, each has coronet of spicules around retractile papilla. General appearance velvety; soft and yielding to touch. In profile, anterior often stepped lower than rest of body . Mantle slightly raised into rim around rhinophore base and into a pronounced collar around gill pocket .
Short and stout, base pale, distally ten to fifteen close set lamellae, and a short nipple like apex. Smooth base often more swollen than lamellate section . Lamellae often with dark brown speckling near apex. Rhinophores stand in distinct pits.
On adults, 15, sometimes 17, large, pale tripinnate gills around contrasting dark brown anus . Basally surrounded by raised collar .
Mouth can project into short tube . Thin oral tentacles only visible from underside.
Sole white or yellowish, split into two layers at anterior; upper layer projects forwards and has cleft at middle . Protrudes at posterior when in motion .
- Up to 60mm long, similar size to many Archidoris pseudoargus.
- Sandy , buff, whitish (Flickr) or bluish white (Flickr), any other marks small and dark.
- Very small tubercles; velvety appearance, soft feel.
- Large pale gills around dark brown anus .
- Base of extended gills surrounded by raised collar .
- Up to 120mm long, half grown ones similar size to Jorunna tomentosa.
- Mantle usually yellow or buff-orange, often with large blotches of bright colours [3Ap].
- Variously sized spiculose tubercles give stiff unyielding feel to mantle.
- Gills often blotched with colour.
- Gills tilt backwards, not upwards from a raised collar.
- Underside of mantle lacks dark markings (may have slight staining at edge) [4Ap].
- Head small with vestigal oral tentacles.
On lower shore and sublittoral fringe. Well camouflaged on prey; Halichondria panicea (EML) and Haliclona spp. ( EML & EML) Simultaneous hermaphrodite. Spawn, February – August in Britain, a spiral ribbon attached by its edge in a tight coil to substrate or food (EML). Planktonic veliger larvae for about three weeks before transforming into adult form.
Southern half of Norway and Faeroes to Adriatic. (GBIF map).
Widespread round Britain and Ireland, but rarely common in one place. (UKinteractive distribution map. NBN.)
Records from Pacific and Africa are probably of other spp. of similar appearance.
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).