information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

A sea slug (Acteon tornatilis)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.
Only coastal and marine records shown



Acteon tornatilis is a primitive sea slug within a thick, opaque, pink, external shell of up to 2-3 cm that is marked by 1-3 white bands on the body whorl and one white band on the remainder. Either side of each band is a narrow margin of dark pink. It is able to withdraw the whole of its body into its shell which is then sealed by an amber-coloured operculum. The shell aperture accounts for two-thirds of the shell length. Inside the lip of the shell is a distinctive tooth. The head of Acteon tornatilis has four large lobes and a cephalic disc that is used in burrowing through clean, fine sand together with a small foot that has blunt, propodial tentacles. Inside of the shell are folded mantle flaps.

Recorded distribution in Britain and Ireland


Global distribution




Depth range


Identifying features

  • Thick, opaque, shell coloured pink.
  • Body whorl is marked with 1-3 white bands.
  • Remaining whorls marked with 1 white band.
  • Each side of the white bands has a narrow margin of dark pink.
  • Distinctive tooth on inside of lip.
  • Head has four large, flattened lobes.

Additional information

Acteon tornatilis is a carnivore, feeding on tubiculous, infaunal polychaetes, including Owenia fusiformis and Lanice conchilega. Acteon tornatilis was previously been known as Tornatella fasciata (pre-1950). Four species of the Acteon genus are found in Europe.

Listed by

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Further information sources

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  1. Allen, J.A. 1962. The fauna of the Clyde Sea area. Mollusca. Millport: Scottish Marine Biological Association.

  2. Bruce, J.R., Colman, J.S. & Jones, N.S., 1963. Marine fauna of the Isle of Man. Liverpool: Liverpool University Press.

  3. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

  4. Foster-Smith, J. (ed.), 2000. The marine fauna and flora of the Cullercoats District. Marine species records for the North East Coast of England. Sunderland: Penshaw Press, for the Dove Marine Laboratory, University of Newcastle upon Tyne.

  5. Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins.

  6. Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press.

  7. Laverack, M.S. & Blackler, D.M., 1974. Fauna & Flora of St. Andrews Bay. Scottish Academic Press (Edinburgh & London).

  8. National Biodiversity Network (NBN) Atlas website. Available from:  Accessed 01 April 2017

  9. Thompson, T. E. & Brown, G. H., 1976. British Opisthobranch Molluscs. London: Academic Press. [Synopses of the British Fauna, no. 8.]


This review can be cited as:

Richards, S. 2008. Acteon tornatilis A sea slug. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 17-08-2018]. Available from:

Last Updated: 08/05/2008