Body
Up to 33mm long. Smooth, translucent white, often revealing brownish viscera [image2]. Yellow or orange medial dorsal ridge on posterior third of body [1]. On each side, from head to behind gills, a reduced mantle rim [2]. Up to seven yellow/orange-tipped, erect, elongate papillae on rim shield the gills [4]. Yellow/orange sometimes absent from body and/or papillae (EML).
Rhinophores
Base smooth. Up to 12 prominent lamellae [2]. Translucent white with yellow or orange pigment distally. Two forward-pointing, basally white, distally yellow/orange, elongate papillae at the base of each rhinophore [3]. Yellow/orange sometimes absent from rhinophores and papillae (EML).
Gills
Three translucent white tripinnate gills, usually with yellow/orange tips, around dorsally situated anus [1].
Head
Sides of head extended into short white oral tentacles [3].
Foot
Translucent white sole. No propodial tentacles or extension [3].
Key identification features
- Two forward pointing elongate papillae at base of each rhinophore [3].
- Several erect elongate papillae on either side of the gills [4].
- No propodial tentacles or extension on foot [3].
- No oral veil with elongate processes.
Similar species
Trapania maculata, T. pallida & T. tartantella
- One or two backward pointing elongate papillae at base of each rhinophore.
- One elongate papilla on either side of the gills.
- Anterior of foot expanded into propodial tentacles.
Polycera quadrilineata & P. faeroensis.
- No elongate papillae at base of rhinophore.
- Oral veil with four or more processes.
- Anterior of foot expanded into propodial tentacles.
Ecology and behaviour
On lower shore and sublittorally to about 100m. Formerly thought to feed on compound ascidians (Thompson & Brown), but kamptozoa living epizoically on other sessile organisms now thought to be the diet (SSF). Simultaneous hermaphrodite. Curved ribbon of spawn recorded in most months. Shelled veliger larvae live as plankton before transforming into adult form.
Distribution and status
Iceland and White Sea to western Mediterranean and eastern USA. (GBIF map). Widespread records round Britain and Ireland. Usually found in small numbers. Occasionally locally common. (U.K. interactive distribution map.NBN.)
References and links
Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.
Rudman, W.B. Sea Slug Forum (SSF)
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 maps:
Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML)
The map provided here shows the distribution of the species based on Conchological Society data.