Caution: There is uncertainty among experienced malacologists about the identification of Aeolidiella spp. Recorders are advised to take clear photographs of their finds for future reference. It is hoped that the situation may be clarified by examination of radulae and DNA sequencing in the future.
Body (excluding appendages)
Up to 40 mm long. Pale translucent whitish, often with fawn (EML) or orange [1] suffusion of varying intensity and extent, occasionally golden [7]. Viscera sometimes show indistinctly brownish or greyish [6]. Dorsum has opaque freckles of white (ScotNud) or a whitish shade of the general body tint [1]. Cerata
Can sometimes conceal most of dorsum, but large amounts often exposed. About 15 closely arranged transverse rows on each side of the body. Translucent white or pinkish revealing pinkish [6], orange-brown [1], grey-brown (ScotNud), or green-brown internal digestive gland, with large white cnidosacs at the tip. Whitish cnidosacs often occupy over half of each of anterior cerata, forming a white ruff like that on A. alderi [3]. Extensive opaque whitish mottling on surface. Rhinophores
Smooth, sometimes slightly wrinkled. Tinted orange [3], of varying intensity, with cream-white apex and pigment flecks on distal part. Head
Translucent white or tinted orange [1], with area between rhinophores and oral tentacles often tinted even when body not. Internal eyes visible [6]. Opaque white internal mouthparts [2] often appear coloured by surface tint. Distance between oral tentacles at base about equal to thickness of tentacle base [1]. Oral tentacles often translucent white, even when rest of head tinted, with white flecks of surface pigment [6]. Foot
Broad; three times as wide as body, narrows to a short fine point at posterior [4].
Curved convex anterior continues into short slender propodial tentacles which may be counter-curved at times [4]. Sole almost transparent colourless, clearly revealing body and its overhanging cerata. Upper surface usually has white pigment flecks around the periphery [6].
Key identification features
Distance between oral tentacles at base about same as thickness of tentacle base [1].
Internal eyes visible through translucent body [6].
Anterior half of body copiously speckled with white pigment which is stained orange, yellow etc. if body so tinted [1].
White pigment speckles on oral tentacles, cerata and, distally, on rhinophores [6].
Body translucent white, anterior often translucent orange [1].
Often, overall pinkish appearance, especially if viewed through translucent foot [4].
Body broad in comparison with A. sanguinea and A. alderi [4].
Anterior cerata may be white and resemble white ruff on A. alderi [6].
Spawn, non-sinuous spiral line [8]; white contents divided into sections by clear breaks [9]; ova small so width of spawn line 5 or 6 times diameter of one ovum [10].
Distance between oral tentacles about 3 times thickness of tentacle base.
Internal eyes not, or barely, visible through opaque pigment.
Dense pigment on rhinophores and dorsum, so not translucent.
Pale triangular mark often in front of rhinophores.
Body broad. Length can be greater than 46mm.
Spawn; large convoluted ribbon, standing upright in water, deposited in spiral.
Has planktonic veliger larvae.
Ecology and behaviour
Sublittoral and occasionally low water spring tide at sheltered sites. Usually where some mud or silt present. Feeds on sea anemones, including Sagartiogeton spp. (EML), Sagartia spp. (EML), Cereus pedunculatus (EML) and Diadumene cincta (EML). Simultaneous hermaphrodite. Spawn deposited in a non-sinuous spiral line [8]; white ova contents divided into sections by several clear breaks [9]; ova small so width of spawn line 5 or 6 times diameter of one ovum [10]. Shelled veliger larvae drift as plankton before settling on the sea floor and transforming into adults.
Distribution and status
Denmark to Bay of Biscay (GBIF map). Widespread in Britain and Ireland, but usually in small numbers. Some old records aggregate A. alderi under A. glauca. (UK interactive distribution map)
References and links
Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.
Anderson, J. Scottish Nudibranchs (ScotNud).
Groeneveld, R. & Reijs, S. Dutch Sea slugs (Diverosa)
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)
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