Phyllodesmium briareum
(Bergh, 1896)

Family: Glaucidae


Known from Tropical western Pacific and Indonesian Archipelago.


UPPER: southern end of Sek Island, Madang, March 1987. [20mm long preserved - WAM391-87]. PHOTO: F.E. Wells,
LOWER: Closeup of animals showing the development of ducts in the body wall and cerata to nurture zooxanthellae, which can be seen as lines of brown specks. Animal 25mm long alive, Tambuli Beach, Mactan Is, Cebu, 20m, March 1983, on Solenopodium stelleri (Fam: Briareidae) Philippines, March 1983. PHOTO: B.E.Picton

Phyllodesmium briareum, like other species of Phyllodesmium, feeds on soft corals and is very well camouflaged when crawling over or nestled between the polyps of the doft coral it is feeding on. It is reported to feed on a number of species of briareid soft coral including Solenopodium stelleri and Briareum stecheri (sensu MacFadyen, 1936). It is also reported from Pachyclavularia violacea a mat forming soft coral with purplish trunks and greenish brown polyps (See Rie Nakano's message below).

The name briareus was apparently given to it by Bergh because of its association with the soft coral Briareum.

As you will see from the Bernard Picton's photo on the right, P. briareum is one of the species of Phyllodesmium which has a symbiotic relationship with zooxanthella. The rows of brown specks in the photo are one-celled plants [zooxanthellae] which are nurtured in specialised ducts of the aeolid's digestive gland, where they continue to grow, reproduce and photosynthesise, providing nutrients for the aeolid.

• Rudman, W.B. (1991) Further studies on the taxonomy and biology of the octocoral-feeding genus Phyllodesmium Ehrenberg, 1831 (Nudibranchia: Aeolidoidea). Journal of Molluscan Studies, 57(2): 167-203.

Authorship details
Rudman, W.B., 1999 (November 25) Phyllodesmium briareum (Bergh, 1896). [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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