The Marine Life Information Network

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


Blue spot slug (Polycera elegans)

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



A distinctive colourful sea slug. The smooth body is orange in colour with brilliant blue blotches that sometimes contain crimson flecks. It has 5 - 7 robust and feathery trilobed gills with iridescent blue-green lines along their ribs. The head may bear up to 22 finger-like projections. It can grow up to 4 cm in length although a maximum size of 4.8 cm has been recorded.

Recorded distribution in Britain and Ireland

Kilkieran Bay, Co. Galway; Sheep Haven, Co. Donegal; Skomer Island, Pembrokeshire; Lundy, south Cornwall.

Global distribution



Found on rocky coasts feeding on the erect bryozoan Bugulina turbinata and probably other species of Bugula.

Depth range


Identifying features

  • Orange colouration with large iridescent blue spots.
  • Rhinophores and gills without sheaths or accessory processes.
  • Frontal veil produced anteriorly into small digitiform papillae.
  • Up to seven large, trilobed gills.

Additional information

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Listed by

- none -


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

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

  3. 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.]

  4. Picton, B. E. & Morrow, C.C., 1994. A Field Guide to the Nudibranchs of the British Isles. London: Immel Publishing Ltd.

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


  1. NBN (National Biodiversity Network) Atlas. Available from:

  2. OBIS (Ocean Biodiversity Information System),  2023. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2023-03-28


This review can be cited as:

Wilson, E. 1999. Polycera elegans Blue spot slug. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 28-03-2023]. Available from:

Last Updated: 14/09/1999