Royal flush sea slug (Akera bullata)

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



Akera bullata is a sea slug that reaches up to 6 cm in length and bears an external shell coloured white to pale brown. The shell is oval-shaped with a flattened tip and up to 6 whorls. The aperture of the shell is almost as long as the length of the shell itself. The well-developed head is marked anteriorly by an indent to give a tongue-like appearance, and extends into a pair of wide, lateral, flat, tentacular lobes. It bears lateral eyes, lacks an operculum and is coloured with blotched, purplish-brown streaks. The body is pale grey to orange but darker on the outer mantle surface and is marked by white or dark spots. The base of the body bears a very large foot that extends into two large lobed parapodia capable of encasing the dorsal and lateral region of the shell. In some individuals a short, white tentacle extends outwards from the posterior end of the shell.

Recorded distribution in Britain and Ireland

Akera bullata has been sighted at scattered locations on all British coasts.

Global distribution

The distribution of Akera bullata extends from the North Sea, Denmark, Norway and the Baltic to the Atlantic and the Mediterranean coasts of France and Spain.


Akera bullata inhabits soft, fine mud to muddy sand, in sheltered bays, from the lower shore to 370 m. It is often found with Zostera marina.

Depth range


Identifying features

  • Oval shaped shell that is flattened tip and has up to 6 whorls.
  • Shell is up to 4 cm long and coloured white to pale brown.
  • Shell aperture almost as long as shell length.
  • Head indented anteriorly, bears wide, flat lobes and marked with purplish-brown streaks.
  • Body pale grey to orange and up to 6 cm in length.
  • Base of body extends into two very large lobed parapodia.

Additional information

Akera bullata is herbivorous during the summer but feeds on sediment throughout the rest of the year. It is capable of swimming by use of its large, lobed parapodia. When disturbed it may excrete a purple coloured fluid from glands within the mantle. It reproduces throughout April to July.

Listed by

- none -


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  10. 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.

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  13. Thompson, T.E., 1976. Biology of Opisthobranch Molluscs, vol. 1. London: The Ray Society.


  1. Centre for Environmental Data and Recording, 2018. Ulster Museum Marine Surveys of Northern Ireland Coastal Waters. Occurrence dataset accessed via on 2018-09-25.

  2. Conchological Society of Great Britain & Ireland, 2018. Mollusc (marine) data for Great Britain and Ireland - restricted access. Occurrence dataset: accessed via on 2018-09-25.

  3. Conchological Society of Great Britain & Ireland, 2018. Mollusc (marine) records for Great Britain and Ireland. Occurrence dataset: accessed via on 2018-09-25.

  4. Fenwick, 2018. Aphotomarine. Occurrence dataset Accessed via on 2018-10-01

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

  6. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2024-06-16


This review can be cited as:

Richards, S. 2007. Akera bullata Royal flush 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 16-06-2024]. Available from:

Last Updated: 12/09/2007