Biodiversity & Conservation

A sea slug - Facelina auriculata

Facelina auriculata

Image Judith Oakley - Facelina auriculata on Ulva lactuca. Image width ca xx cm.
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Distribution map

Facelina auriculata recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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Facelina auriculata is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Mollusca Snails, slugs, mussels, cockles, clams & squid
Class Gastropoda Snails, slugs & sea butterflies
Authority (O F Müller, 1776)
Recent synonyms Facelina auriculata var. coronata
Map icon Recorded Distribution in Britain and Ireland Recorded from all round Britain and Ireland except east and southeast England.
Habitat information icon Habitat information Found under boulders in the intertidal and sublittoral on its prey species of hydroids, which include Tubularia sp., Obelia geniculata and Clava sp.
Text page icon Description Facelina auriculata is a slender sea slug up to 38 mm in length. It has a white body and numerous small purple cerata. The oesophagus is also visible just behind the rhinophores through the slightly translucent body. There are three pairs of processes at the front end of animal. Closest to the substratum are the short propodial tentacles, which are part of the foot, and are at 90° to the body in a relaxed animal. The much longer oral tentacles project from either side of the mouth and appear forward of the propodial tentacles in an extended animal. Behind the oral tentacles on the top of the animal are the rhinophores, which have a ribbed appearance.
Identifying features
  • White body up to 38 mm in length.
  • Back covered with numerous short cerata, which have a blue/purple hue and are streaked with white.
  • Propodial tentacles, long oral tentacles and annulate rhinophores present, all streaked with white.
  • Red oesophagus is visible through the body.
Additional information icon Additional information The taxonomy of Facelina auriculata is confusing. Until recently two varieties were recognised: var. coronata and var. curta. Facelina auriculata var. coronata is now synonymous with Facelina auriculata while var. curta is recognised as Facelina bostoniensis.

This review can be cited as follows:

Ken Neal 2007. Facelina auriculata. A sea slug. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 26/11/2015]. Available from: <>