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

Solar-powered sea slug (Elysia viridis)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.



Elysia viridis has a delicate leaf-shaped body up to 5 cm in length which tapers posteriorly. This species is commonly vivid green, and occasionally bright red or brown. Tiny glistening red, blue or green spots are also present. Both body length and colour are determined by diet. White patches may be found on the edges of the projections of the foot (parapodium) and around the eyes, and black markings may sometimes be present on the head and body. The parapodium is broad, with lobed or frilled edges and extends almost the entire length of the body, containing visible green chloroplasts. Lateral parapodial "wings" may be outstretched or held over the body. The head bares conspicuous propodial tentacles and a pair of enrolled rhinophores that open ventrally and usually have white distal ends (anus present under right rhinophore). Digestive diverticula which contain ingested chloroplasts, ramify and can be visible through the surface of the body, parapodia and rhinophores.

Recorded distribution in Britain and Ireland

This species probably distributed throughout the British Isles, although most records are from the western coats.

Global distribution



This species can be found on the underside of macroalgal fronds in shallow water and rock pools. Elysia viridis feeds usually on Codium sp. or Cladophora sp. in European waters.

Depth range


Identifying features

  • Body up to 5 cm long.
  • Commonly vivid green, occasionally bright red or brown.
  • Tiny glistening red, blue or green spots.
  • Enrolled rhinophores.
  • Parapodia broad and extends most of body length.
  • Lateral parapodial 'wings' outstretched or folded over dorsum.

Additional information

Elysia viridis is very similar to the sea hare in its soft winged body and colouration, although Elysia sp. is flatter with no oral tentacles. Elysia viridis is known as a 'sap-sucking slug' and feeds only on a single or limited food source (stenophagous). It ingests the chloroplasts unharmed and uses them for photosynthesis which benefit the slugs food supply (a process known as klepoplasty). Chloroplasts account for the colouration of the animal.

This species has a 12-15 month life-span and is sexually mature when 1.2 cm in length. It produces benthic egg masses from April to October which hatch as planktonic veligers. This species may also tolerate low salinity levels.

Listed by

- none -

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. Crothers, J.H. (ed.), 1966. Dale Fort Marine Fauna. London: Field Studies Council.

  4. Dipper, R., & Powell. A., 1984. Field guide to the water life of Britain. London: Reader's Digest Association Limited.

  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. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  8. Jensen, K.R., 1989. Learning as a factor in diet selection by Elysia viridis (Montagu) (Opisthobranchia). Journal of Molluscan Studies, 55, 79-88.

  9. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line]

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

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

  12. Trowbridge, C.D., 2000. The missing links: larval and post-larval development of the ascoglossan opisthobranch Elysia viridis. Journal of the Marine Biological Association of the United Kingdom, 80(6), 1087-1094.


This review can be cited as:

Rowley, S.J. 2006. Elysia viridis Solar-powered 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 22-09-2018]. Available from:

Last Updated: 19/09/2006