A sea slug (Aldisa zetlandica)

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



The mantle is usually white or translucent white with white specks, but has also been recorded as greenish grey (Picton & Morrow, 1994). The gills and rhinophores are also white in colour, with bushy gills which are fully retractable into a pocket. The body is elongate oval with high sides, and the dorsum is covered with large and small conical tubercles. It has short blunt auriculate tentacles on the head. The sides of the foot are tall, and whilst the mantle is not wide it covers the head and foot. Blue or brown digestive glands (the gut) may be seen through the body. Maximum recorded size 35 mm.

Recorded distribution in Britain and Ireland

Reported from Shetland, western Scotland and the west coast of Ireland.

Global distribution

Reported from Shetland south to the Azores.


Found subtidally, this species was originally found through dredging in deep water in Shetland. May occur in depths from 25 to 1900 m but mainly between 70 to 320 m. Also reported from sponge rich areas amongst Axinellid sponges.

Depth range


Identifying features

  • White-translucent body with white specks
  • Rounded profile
  • 5 bushy gills
  • Dorsum covered with large and small conical tubercles
  • Foot is more elongate and narrower than other Aldisa species

Additional information

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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. Millen, S.V. & Gosliner, T.M., 1985. Four new species of dorid nudibranchs belonging to the genus Aldisa(Mollusca: Opisthobranchia), with a revision of the genus. Zoological Journal of the Linnean Society

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

  4. Picton, B.E. & Costello, M.J., 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. [CD-ROM] Environmental Sciences Unit, Trinity College, Dublin.

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

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

  7. WoRMS 2007. The World Register of Marine Species (WoRMS). http://www.marinespecies.org, 2008-10-31


  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-07-21


This review can be cited as:

Sweet, N. A. 2008. Aldisa zetlandica A sea 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 21-07-2024]. Available from: https://marlin.ac.uk/species/detail/173

Last Updated: 24/07/2008