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

A sea slug (Facelina bostoniensis)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.
Only coastal and marine records shown



Up to 5.5 cm long with a translucent white body that is tinged rose-pink, Facelina bostoniensis is the largest facelinid nudibranch in British waters. The area surrounding the mouth is typically red and the red oesophagus is visible externally behind the rhinophores. The rhinophores bear up to 30 conspicuous lamellae and are shorter than the oral tentacles, which can be half the body length. The dorsal cerata are arranged in up to 8 clusters.

Recorded distribution in Britain and Ireland

Found all around the British Isles, but less common around the southeast coast of England.

Global distribution

Found on both sides of the North Atlantic Ocean. In Europe from southern Norway to the Iberian Peninsula and the Mediterranean.


Found sublittorally on species of the hydroid Tubularia, or intertidally on species of the hydroid Clava

Depth range


Identifying features

  • Body translucent white, with red oral area and oesophagus.
  • Oral tentacles longer than rhinophores, up to 1/2 length of body.
  • Cerata arranged in up to 8 clusters.
  • Cerata up to 1/3 to 1/2 body length.

Additional information

The taxonomic history of Facelina bostoniensis is complicated, and was only relatively recently recognised as being conspecific with Facelina auriculata var. curta. Facelina bostoniensis has a broader body, longer cerata, which can be 1/3 to 1/2 of the body length and lacks a blue irridescent sheen distinguishing it from Facelina auriculata

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Further information sources

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    This review can be cited as:

    Hosie, A.M. 2008. Facelina bostoniensis 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 17-08-2018]. Available from:

    Last Updated: 04/12/2008