Up to 9mm long. Depressed dome profile [image1]. Outline elliptical, equally rounded at both ends . Whitish, tinted sandy or rosy, translucent mantle reveals long glistening internal spicules arranged transversely on dorsum, obliquely on subdorsum and radially on flanks. Internal eyes faintly visible through lens. Central area of dorsum shows orange or purplish viscera. Surface covered in long soft tubercles, unobtrusive as colourless transparent . Small reddish, orange, or purple-brown spots arranged in about six longitudinal lines between the gills and rhinophores, and about three concentric lines on the flanks .
Faintly yellowish with up to ten lamellae obliquely pointing upwards to the fore . Sometimes, a ring of tubercles forms a slight sheath around the rhinophore pit .
White anal papilla surrounded by up to 12 yellowish white translucent unobtrusive gills in a circle with small gap at posterior .
Flattened oral lobes form large white oral veil , may be tinted faintly brown near mouth.
Sole translucent white, clearly showing asymmetric orange-brown liver which extends forwards on the left of the animal . Anterior edge curves backwards around the mouth. Ample mantle extends well beyond foot and head, revealing its shining spicules when viewed ventrally.
Key identification features
- Very depressed profile. .
- Long soft non-spiculate tubercles on mantle. .
- Small spots arranged in lines on mantle. .
- Very translucent, revealing long aligned shiny spicules. .
- Asymmetric orange-brown liver extends forwards on left of animal .
- Length 9mm maximum, usually smaller.
- Profile convex.
- Small rounded spiculose tubercles on mantle.
- Brown marks scattered randomly on mantle.
- Translucent, revealing spicules near mantle periphery.
- Symmetric brownish yellow liver.
- Length 8mm maximum, usually smaller.
- Pear-shape purple-black liver visible through sole. [3Oi]
- Abundant small round-tipped tubercles on mantle (not swollen or club-shaped) [3Oi].
- Often, dark tubercular processes within gill circle. [5Oi]
- Scattered random brown freckles, and often black flakes, on mantle. [1Oi].
Ecology and behaviour
Low water spring tide and sublittorally to 15m. On hard substrate, on or near its prey, Schizomavella linearis (EML) on underside of stones. Spots on mantle resemble zooids of the bryozoan prey. Simultaneous hermaphrodite. Spawn; a thin pink line deposited in a tight neat spiral of about ten turns.
Distribution and status
Distribution beyond Britain, Ireland and north French coast (GBIF map) is uncertain because of possible confusion with similar species in Mediterranean and a large area of the Indo-Pacific (SSF). Regarded as rare in Britain, but probably overlooked as small, translucent and low profile. Occurs fairly regularly on Orkney shores.
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 fact sheets (SSF).
Thompson, T.E. 1976. Biology of opisthobranch molluscs 1. 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 maps and prey organisms
Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML)