Synonyms
Polycera ocellata Alder & Hancock;
Body
Up to 20mm long. Edge of reduced mantle forms a short frontal veil, cleft at centre, with about 8 short pale lobes [image1]. Mantle edge continues from veil as a tuberculated ridge along each side to rear of gills, terminating in large, bright white, slightly branched branchial lobe [2]. Ground colour of body dark brown to olive green or grey-green, broken into a network by numerous broad low pale tubercles. Translucent, showing fawn viscera near gills. Colours paler on juveniles [10].
Rhinophores
Tall, coloured as body, smooth conical base, 7- 9 widely spaced yellow tinted lamellae [6] . Apex produced with low domed summit. On 2mm juveniles, stem shorter, 6 lamellae [5].
Gills
Three, or five, near highest point of dorsum [4]. Partially tripinnate, pale shade of body colour, often with fawn marks.
Head
Ventrally, semicircular, yellowish mottled dull green [7]. Surrounds of mouth swollen, meeting to form a Y. Folded, flattened, rectangular, lateral oral-lobes [3]. Dorsally, mantle edge forms lobed veil [1].
Foot
Sole yellowish mottled dull green [7]. Translucent; fawn viscera visible through sole below gills. Propodial expansion can extend [3] and contract [4]. When animal viewed laterally, upper surface of foot periphery forms grey-white band sprinkled with dull green around base of body [4]. Foot often folded together [8] when removed from thin stemmed polyzoan prey.
Palio dubia (EML)
- Small isolated tubercles, not breaking ground colour into a network.
- 12 or 13 closely packed lamellae on short stout rhinophore.
- Sublittoral, rarely if ever intertidal. (Many records confuse/combine P.dubia and P.nothus.)
On lower shore, and sometimes sublittorally to 30m, feeding on Bowerbankia spp. (Natuurlijkmooi) Difficult to detect on shore; best sought by examination under magnification of sessile polyzoans in water. Simultaneous hermaphrodite. Spawn mass a laterally compressed cylinder (Seaslugforum) deposited April - September in a loose angulated coil, whitish or tinted rose.
Britain, Ireland, southern Sweden and coasts up to Arctic Circle on both sides of North Atlantic, but some off-shore records may be P. dubia ( GBIF map). Mediterranean records uncertain because of confusion/combining of P. dubia with P.nothus, but correctly identified 2011 from Croatia [9]. Scattered finds around Britain and Ireland, but probably under recorded because of its camouflage. (UK interactive distribution map.NBN.)
Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.
Johnston,G. 1838. Miscellanea zoologica. Ann. Mag. nat. Hist. 1: 114-125. Free PDF (page 124) at http://biodiversitylibrary.org/bibliography/4227#/summary
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).