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 46 mm long. Slender in comparison with A. glauca. Translucent reddish orange (Flickr), orange (SSF) or yellow (Flickr), often paling towards posterior. No surface pigment marks.
Cerata
Neatly arranged roundly tipped cerata cover most of body, except, often, a narrow dorsal strip running its length [image2]. Arranged in about 15 rows on each side. Translucent blood-red, orange or yellow revealing orange-brown [1] to red internal digestive gland, and white cnidosac at tip. No surface pigment.
Rhinophores
Bases closely positioned. Often wrinkled [2].Same colour as body, or a more intense hue, with distinctly demarcated white tips. No surface pigment.
Head
Often transversely wrinkled, coloured as anterior of body, no surface pigment, internal eyes visible. Oral tentacles coloured as head, with white tips, and longer than rhinophores [3]. Space between oral tentacles about same as their thickness at base.
Foot
Anterior convex and drawn out into distinct short counter- curved propodial tentacles [3]. Sole translucent white. Short slender posterior tip often protrudes beyond cerata.
The three species of Aeolidiella in GB and Ireland are difficult to distinguish. Well focussed photographs are recommended for confirmation of records.
- Distance between oral tentacles at base about same thickness as tentacle base. [3]
- Internal eyes visible through translucent body [2].
- No surface pigment on body, tentacles, or cerata.
- Rhinophores have distinctly demarcated white tips.
- Body translucent blood-red, orange [1] or yellow, including surfaces of cerata. .
- Body slim in comparison with A. glauca and Aeolidia papillosa.
- Cerata arranged tightly and neatly, often with narrow uncovered dorsal strip running whole length of body.
- Cerata more bluntly tipped than other Aeolidiella spp.
- Spawn; a spiral non-sinuous line.
- Has planktonic veliger larvae.
- Anterior convex and drawn out into distinct short counter- curved propodial tentacles [3].
- Aeolidiella alderi
- Eyes visible, oral tentacles spaced as A. sanguinea.
- White pigment distally on rhinophores, oral tentacles and cerata; no other pigment.
- Body translucent white, yellow, or red. (Red ones may be confused with A. sanguinea.(SSF)
- Body slim in comparison with A. glauca and Aeolidia papillosa.
- Cerata more loosely arranged than A. sanguinea.
- White anterior ceratal ruff shows clearly on some specimens.
- Spawn; sinuous line loosely arranged in rounded patch (Nembro).
- Lacks planktonic veliger larvae.
- Anterior expanded into short triangular propodial tentacles which continue the curve of the foot (not counter-curved).
- Aeolidiella glauca
- Eyes visible, oral tentacles spaced as A. sanguinea.
- Anterior half of body copiously speckled with white pigment which is stained orange, yellow etc. if body so tinted.
- White pigment speckles on oral tentacles, cerata and, distally, on rhinophores.
- Body translucent white, anterior often translucent orange.
- Often, overall pinkish appearance, especially if viewed through translucent foot.
- Body broad in comparison with A. sanguinea and A. alderi.
- Anterior cerata may be white and resemble white ruff on A. alderi.
- Spawn; a spiral non-sinuous line, white contents divided into sections by breaks (Diverosa).
- Has planktonic veliger larvae.
- Aeolidia papillosa
- 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.
Low water spring tide and sublittorally on hard substrate. Feeds on sea anemones; reports include Sagartia spp. (EML), Sagartiogeton undata (EML), Diadumene cincta (EML), Cereus pedunculatus (EML), Aiptasia couchi and Actinea equina (EML). Simultaneous hermaphrodite. Spawn; a non-sinuous spiral line. Veliger larval stage in plankton before metamorphosis.
Ireland, west coast of Britain and Atlantic coasts of Portugal and France (GBIF map). The rarest of the three Aeolidiella spp. found in Britain; very few confirmed records (UK interactive distribution map. NBN).
The map provided here shows the distribution of the species based on Conchological Society data.
Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.
Groeneveld, R. & Reijs, S. Dutch Sea slugs (Diverosa)
Rudman, W.B. Sea Slug Forum (SSF)
Thompson, T.E. 1976. Biology of opisthobranch molluscs 1. 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)
Acknowledgement
The help and advice of Dr Bernard Picton and Dr Julia Nunn are gratefully acknowledged, but their endorsement of every detail is not implied.