Cyerce nigricans
(Pease, 1866)

Family: Caliphyllidae


Originally described by Pease from the `Pacific Islands', it is widely distributed in the Indo-West Pacific.


UPPER: Guam, Bile Bay, reef flat; 22mm long; 2 April 1971. Host: Chlorodesmis fastigiata. PHOTO: Clay Carlson.
LOWER: Reef flat near Gorgonia Hole, Heron Is, Great Barrier Reef, Queensland, May 1981. PHOTO: Bill Rudman.

Although most species of Cyerce, and the related genus, Polybranchia, are cryptically coloured, Cyerce nigricans breaks the rule. It is one of the 'icon' species of the Great Barrier Reef, often being used in tourist posters and brochures. As with many brightly coloured sea slugs this species produces distasteful secretions, and the cerata are easily cast (autotomy)when the animal is disturbed. Distasteful secretions and autotomy are two common defensive strategies sea slugs use against predatory fish.

I have put a 'species' or 'colour form' described by Bergh from Palau as Cyerce nigra, on a separate page. It seems to have consistent colour differences.

• Pease, W.H. (1866). Remarks on nudibranchiata inhabiting the Pacific islands, with descriptions of two new genera. American Journal of Conchology 2(2): 204-208.

Authorship details
Rudman, W.B., 1999 (July 6) Cyerce nigricans (Pease, 1866). [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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