Synonym: Eubranchus farrani (Alder & Hancock, 1844)
Body (excluding appendages)
Up to 20 mm long, (to 23mm in Mediterranean). Elongate, with posterior often extending far beyond cerata . Translucent white, or greyish white, with scattered blotches and spots of orange or yellow surface pigment . Variants have whole body tinted orange, or brown flesh with orange pigment (Flickr), or the orange pigment ringed blue (ScotNud), or, in the case of juveniles, all white. (See ScottishNudibranchs for range of colour forms.)
Arranged in up to ten groups along each side, leaving much of of the dorsum exposed . Cerata frequently altering shape, but always moderately expanded, the larger ones more markedly. White, only faintly, if at all, revealing pale brown internal digestive gland. Occasionally surface brown instead of white (Flickr). Prominent subterminal orange or yellow band surrounds small white apical tip. Orange/yellow pigment band sometimes absent, or whole ceras orange/yellow.
No lamellae, but may be wrinkled. Orange distally , or entirely except for small white tip .
Broad slightly convex anterior edge. White, often with orange patch. Small black eyes set back from rhinophores . Oral tentacles distally, or entirely, orange, spaced widely apart on top of lip .
Linear, tapering gradually to a slender point at posterior. Anterior rather truncated and slightly wider than rest of foot, but no propodial extension or tentacles . Sole translucent white, revealing viscera and ovotestis lobules when fed and mature.
Key identification features
- Less than 20mm long.
- Cerata smooth, changeable, but always at least moderately inflated .
- Part of dorsum not concealed by cerata .
- Usually orange pigment blotches on body.
- Usually orange subterminal band on cerata.
- Rhinophores and oral tentacles, part or completely orange.
Eubranchus pallidus (Alder & Hancock, 1842))
Inflated smooth cerata distally white with sub-apical gold ring.
Mahogany and white pigment marks, never greenish.
Basal mahogany mottling on white translucent rhinophores and oral tentacles.
Band of mahogany two-thirds way up rhinophores and half way up oral tentacles.
Part of dorsum not concealed by cerata.
Eubranchus tricolor Forbes, 1838.
Cerata smooth, like flattened rugby balls.
Dorsum concealed by crowded cerata (up to 150).
Body pale yellow or greyish white.
Subterminal golden-yellow and white bands on cerata.
Inside cerata; indistinct red-brown digestive gland often tinged violet distally.
Rhinophores and oral tentacles; pale yellow-brown with paler tips.
Ecology and behaviour
Low water spring tides and sublittorally to 30m. Eats hydroids, including Obelia geniculata (EML). Simultaneous hermaphrodite. Spawn a curved ribbon (ScotNud), recorded in spring and summer.
References and links
Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.
Anderson, J. Scottish Nudibranchs (ScotNud) (Wide range of colour forms shown.)
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).