Body (excluding appendages)
Usually up to 10 mm long, exceptionally 18mm. Translucent greyish white with many blotches of brown [image1] or olive surface pigment, and a few isolated random white marks.
Cerata
Usually 4 or 5, exceptionally 7, groups along each side of the dorsum. Each group usually has one large ceras with 0 - 2 smaller ones [2]. Specimens 2.5mm long may have very few cerata and much exposed dorsum [7]. Ceras is urn-shape [4], constantly expanding and contracting. Apex narrows rapidly to a nipple-like point. Transparent revealing yellowish, peach [2], pale brown or red [7] internal digestive gland which is noticeably narrower than the inflated ceras [5]. Apex has band of mingled brown and white surface pigment flecks around clear extreme tip, then narrow band of white flecks [2]. Rest of ceras has 2 or 3 indistinct encircling bands of brown or olive surface pigment flecks, like those on body, and scattering of white flecks.
Rhinophores [1]
Smooth, translucent whitish with opaque white apical band (extreme tip clear) and subapical brown band. Sometimes a second brown band.
Head
Oral tentacles about half length of rhinophores, and similarly banded, but much less distinctly, so white pigment may be almost absent [1]. Large mouthparts protrude well in front of foot.
Foot [3]
Anterior rather truncated, no propodial tentacles or lobes. Sole greyish white, edged by brown or olive line on the body.
- Almost always present where E. exiguus found.
- Small, frequently less than 6mm, usual maximum 8mm.
- Smooth slender cerata arranged singly.
- Brown digestive gland zig-zags between cerata.
Eubranchus doriae (Trinchese, 1874)
- Rarely recorded; south and west coasts GB & Ireland.
- Small, maximum length 12mm.
- Pronounced tubercles on surface of cerata.
- Olive or brown blotches on body, no zig-zag digestive gland.
Eubranchus cingulatus (Alder & Hancock, 1847)
- Up to 29mm long.
- Up to 10 rows of smooth slender cerata each side; about 10 per row.
- Olive or brown blotches on body, no zig-zag digestive gland.
Lower shore and sublittorally to 40m. On hydroids growing on stones, Laminaria fronds, piers etc. Eats Obelia geniculata (EML) on fronds of Laminaria hyperborea growing in moderate wave exposure, and many other hydroids, such as Laomedia flexuosa (WoRMS) on sheltered shores and in estuaries down to 7 ppt salinity. Simultaneous hermaphrodite. Kidney-shape transparent spawn capsules, each containing about 30 white ova [6], in spring and summer. Spawn capsules easier to detect, and more numerous, than adults, but difficult to distinguish from spawn of T. tergipes. Embryology and development uncertain because of confusion with other spp.. Probably a veliger stage and several generations p.a..
Baltic, Mediterranean, and Arctic to Spain and east USA (GBIF map). Densities of 200 /m² recorded in Netherlands. Scattered records; probably common all round Britain and Ireland, but overlooked as small size requires searching of hydroids under magnification. (UK interactive distribution map NBN.)
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 maps and prey organisms
Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML)