Cuthona caerulea
(Montagu, 1804)

Family: Tergipedidae


Commonly found in western Europe from the western Mediterranean and along the Atlantic coast to sweden and southern Norway. Thompson & Brown (1984) give references to localities in the western Atlantic from Sao Paulo, Brazil to Florida, USA. Usually sublittoral.


Two specimens from Cerbere, on the Mediterranean coast of France. Upper: crawling over the sponge Aplysina aerophoba. July 05, 2002. Site : La Ramere., Depth : 8m, Size : 10-12mm
Lower: July 01, 2002. Site : Les 3 moines., Size : 1cm. Photos: Marina Poddubetskaia

This brilliantly coloured animal grows to about 25mm long. It is quite variable in colour with Thompson & Brown (1984) summarising the variation in the cerata. The digestive gland duct can vary from black, or various shades of blue, to green. The ceratal wall always has a subterminal band of yellow, red or orange. Usually there is band below this of blue, turquoise or green, but it can sometimes be absent. There is a third band bleow this which is always the same colour as the top band, although it can often be fainter and fades towards the ceratal base. Like most tergipedids it feeds on hydroids.

Authorship details
Rudman, W.B., 2000 (May 20) Cuthona caerulea (Montagu, 1804). [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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