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Aeolidiella alderi (Cocks, 1852)

Author & date of last revision: Ian Smith on 24 October 2012
Eolida soemmerringii auctt. [ICZN suppressed]; Eolis glauca Alder & Hancock, 1845 (part);

Notes

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.

Description

Body (excluding appendages)
Up to 37mm long. Usually translucent white, often revealing colour of pinkish ovotestis in posterior half [1]. Body may be strongly tinted yellow or red (SSF), but lacks mottling of surface pigment [2].

Cerata
About 15 obliquely transverse rows on each side of the body, mobile, and often held to reveal anterior half of the dorsum. Usually translucent white, but sometimes tinted red or yellow, revealing internal digestive gland of some shade of brown, varying with diet. Whitish cnidosacs partly obscured by white surface pigment at tips, but anterior group has unusually large cnidosacs occupying distal half, or more, forming a white ruff [3]. Rest of ceras has very faint traces of surface pigment. On red or yellow specimens, the surface pigment may be yellow.

Rhinophores
Smooth, usually white with white pigment distally. On red or yellow specimens rhinophores may be similar colour, with yellow distal pigment.

Head
Coloured as body. Eyes visible [2]. Oral tentacles with white distal pigment [2], or yellow pigment if body red or yellow. Space between oral tentacles about same as thickness of base [2].

Foot
Translucent white. Anterior expanded into short triangular propodial tentacles which continue the curve of the foot (not counter-curved) [1].

 

Key identification features

  • Distance between oral tentacles about same thickness as tentacle base.
  • Internal eyes visible through translucent body.
  • White or yellow pigment distally on rhinophores, oral tentacles and cerata.
  • Body translucent white, yellow, or red. Red ones may be confused with A. sanguinea (SSF).
  • Lacks opaque freckles on dorsum.
  • Front group of cerata make a white ruff, but A. glauca can be similar.
  • Cerata more loosely arranged than A. sanguinea.
  • Spawn; sinuous line of large ova deposited in loose indistinct circle. (Nembro)
  • Lacks planktonic veliger larvae. 
  • Anterior expanded into short triangular propodial tentacles which continue the curve of the foot (not counter-curved).

Similar species

  • Aeolidiella glauca 
  •  Eyes visible, oral tentacles spaced as A. alderi.
  • 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.

 

  • Aeolidiella sanguinea
  • Eyes visible, oral tentacles spaced as A. alderi.
  • No surface pigment on body, tentacles, or cerata.
  • Rhinophores have distinctly demarcated white tips.
  • Body translucent red, orange 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 non-sinuous spiral line.
  • Has planktonic veliger larvae.
  • Anterior convex and drawn out into distinct short counter- curved propodial tentacles [3As] 

 

  •  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.

Ecology and behaviour

Lower shore and shallow sublittoral. Eats anemones, including Actinithoe sphyrodeta (EML), Cereus pedunculatus (EML), Metridium senile (EML), Diadumene cincta (EML), Sagartia spp. (EML), Sagartiogeton lacerata (EML) and Parastephanauge pauxi. Before feeding, the anterior white ruff of cerata may elongate and shoot nematocysts into the prey. Simultaneous hermaphrodite. Spawn a sinuous line of large ova arranged in a loose indistinct circle (Nembro). No planktonic veliger stage.

Distribution and status

Mediterranean to Britain, frequent in Portugal (GBIF map). Uncertainty because of confusion with other Aeolidiella spp. Most records in GB & Ireland from Ireland and south coast of England (UK interactive distribution map.)
 

References and links

Alder, J. & Hancock, A. 1845-1855. A monograph of the British nudibranchiate mollusca. London, Ray Society.

Groeneveld, R. & Reijs, S. Dutch Sea slugs (Diverosa)

NEMBRO nudibranchs (Nembro)

Rudman, W.B. Sea Slug Forum (SSF)

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 map and prey organisms
Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML).
 

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Aeolidiella alderi. Typical specimen; white body and tentacles with distal pigment. Brown-filled cerata, except white anterior ruff. No pigment on dorsum. Triangular propodial tentacle continues curve of foot. Lough Hyne, Co. Cork, Ireland.
Image © Graham Day
Aeolidiella alderi. Typical specimen; white body and tentacles with distal pigment. Orange-brown filled cerata, except white anterior ruff. No pigment on dorsum. Eyes clearly visible behind rhinophores. May 2012. Worms Head, S. Wales.
Image © D.Kipling

Additional images

  • Aeolidiella alderi. Typical specimen; white body and tentacles with distal pigment. Pale brown filled cerata, except white anterior ruff. No pigment on dorsum. Eyes clearly visible behind rhinophores. May 2012. Worms Head, S. Wales.

GALLERY of larger images of this species.
All images copyright; see 'image details'.

Recorded UK distribution