Eubranchus exiguus
<p><em>Eubranchus exiguus</em> (Alder & Hancock, 1848)</p>
Eubranchus exiguus
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.)
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..
- 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.
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)
Body (excluding appendages)