Up to 8mm long. Broad oval outline [image5], discoid at rest . Low profile . Mantle covers whole body. Ground colour light, sometimes pinkish, often mostly concealed by brown pigment; grey-brown peripherally, but warmer brown dorsally due to orange-brown viscera showing through translucent mantle. Often, ground colour restricted to wide lines breaking brown pigment into blocks , especially round periphery, where pale lines alternate with dark blocks. Illustration in Alder & Hancock shows very little brown . Mantle has many small round-topped spiculose tubercles with translucent grey-brown coating. When viewed directly from above, the underlying light opaque interior of tubercle shows as pale spot outlined by grey-brown epithelium , occasionally with a smaller, dark, apical spot. Some pale tubercles connected to each other by lines of pale ground colour.
Apex truncated. Translucent pale greyish with up to nine widely spaced, robust, dark, oblique lamellae . At rhinophore base: the pit, three or four large splayed tubercles and surrounding area distinctly contrast (lighter or darker) with the adjacent mantle.
Up to 10 translucent grey-brown gills with base colour distinct from adjacent mantle . Black-brown tubercular processes within gill circle.
Large oral veil and large depression at orifice .
Nearly as wide as mantle. Sole translucent whitish, showing central elongate orange-brown, or brownish-salmon, liver . Anterior of foot rather truncate, may slightly curve back from mouth. Posterior tip may sometimes protrude beyond mantle.
Key identification features
- Orange-brown liver visible through sole .
- Mantle usually brown, peripherally dissected into blocks by wide, light, unpigmented lines .
- Around rhinophore base: pit, large tubercles and rim are distinctly lighter or darker than adjacent mantle .
- Lamellae on rhinophores thick and widely spaced .
- Tubercles may appear as pale spots with dark outline .
- Pear-shape purple-black liver visible through sole.
- Abundant small round-tipped tubercles on mantle (not swollen or club-shaped).
- Often, dark tubercular processes within gill circle.
- Scattered random brown freckles, and often black flakes, on mantle.
- Flat topped club-shape tubercles on mantle.
- Usually, no dark pigment marks.
- Club-shape tubercles with obtusely pointed apices.
- Usually, no dark pigment marks.
- Orange-brown liver visible through sole.
- Randomly arranged brown pigment marks on mantle.
- Brown pigment marks arranged in longitudinal lines on mantle.
- Asymmetric orange-brown liver extends forwards on left of animal.
- Very depressed profile.
- Long soft non-spiculate tubercles on mantle.
Ecology and behaviour
On lower shore and sublittorally. Feeds on Cellepora pumicosa (EML) and Porella concinna. Reproductive details unknown.
Distribution and status
Orkney, southern Sweden, Britain and Ireland, and Brittany (GBIF map). Scattered records around Britain and Ireland, but uncommon.
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).