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

A sea slug (Doto fragilis)

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



The body of Doto fragilis varies from light to dark brown with larger specimens tending to be darker. White patches or spots occur along the the sides of the body, particularly on the dorsum and on the margins of the oral veil, which is expanded into lobes. The rhinophores are long, slender and smooth, with trumpet shaped sheaths which flare at the outer rim. Up to 10 pairs of large tuberculate cerata are present in two rows along the sides of the body, each with up to 13 concentric circles of pale tubercles. Maximum recorded size is 34 mm.

Recorded distribution in Britain and Ireland

Found all around the British Isles.

Global distribution



Doto fragilis occurs up to 200 m depth. This species is known to feed on the hydroids Nemertesia antennina, Nemertesia ramosa, Halecium halecium and Halecium muricatum.

Depth range


Identifying features

  • Brown hue in skin but no dark surface pigment spots
  • White glands along flanks of body
  • Up to 10 pairs of cerata, each with up to 13 concentric circles of pale tubercles

Additional information

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Listed by

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Further information sources

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  1. 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.]

  2. Hunnam, P. & Brown, G., 1975. Sublittoral nudibranch mollusca (sea slugs) in Pembrokeshire waters. Field Studies, 4, 131-159.

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

  4. OBIS,  2018. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2018-09-25

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

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

  7. Thompson, T.E. & Brown, G.H., 1984. Biology of Opisthobranch Molluscs, vol. II. London: Ray Society.

  8. Thompson, T.E., 1972. Eastern Australian Dendronotoidea (Gastropoda: Opisthobranchia). Zoological Journal of the Linnean Society, 51(1), 63-77

  9. Thompson, T.E., 1988. Molluscs: Benthic Opisthobranchs. London: Bath Press. [Synopses of the British Fauna New Series), (ed. Doris M. Kermack & R.S.K. Barnes), no. 8 (second Edition)].

  10. WoRMS 2007. The World Register of Marine Species (WoRMS)., 2008-10-31


This review can be cited as:

Sweet, N. A. 2008. Doto fragilis 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 25-09-2018]. Available from:

Last Updated: 07/08/2008