Phyllodesmium horridum
(Macnae, 1954)

Family: Glaucidae


Southern tip of South Africa from Cape of Good Hope to Sodwana Bay.


Brazenhead, Eastern Cape, South Africa, 25m, July 2001. 40mm long. Photo: Valda Fraser.

Body translucent cream to orange, with viscera showing through. There is an opaque white median dorsal band, of irregular width, running along the back of the animal, and an opaque bluish-white band along the upper side of each ceras.

Some authors consider this South African species to be synonymous with Phyllodesmium serratum, which is known from Australia and Japan, but I have shown consistent differences (Rudman, 1991) which suggest they should be considered distinct species. The most distinctive external difference is the broad opalescent or opaque bluish-white dorsal band down each ceras in P. horridum which has no equivalent in P. serratum, and in P. horridum the denticles on the radular teeth are much coarser than in P. serratum.

Gosliner reports that this species feeds on the gorgonian Melitodes.

• Rudman, W.B. (1981) The anatomy and biology of alcyonarian feeding aeolid opisthobranch molluscs and their development of symbiosis with zooxanthellae. Zoological Journal of the Linnean Society, 72: 219-262.
• 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., 2001 (August 9) Phyllodesmium horridum (Macnae, 1954). [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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