Protaeolidiella atra
Baba, 1955

Family: Aeolidiidae


Tropical Indo-West Pacific


UPPER: On its food, the athecate hydroid, Solanderia fusca, 27mm long.
MIDDLE: Solanderia colony stripped of all polyps, with three Protaeolidiella egg masses.
LOWER: showing how well camouflaged Protaeolidiella is on Solanderia, 20mm long. Heron Is, Great Barrier Reef, Queensland, June 1983.
PHOTOS: Bill Rudman.

Protaeolidia atra is a rather unusually shaped member of the Aeolidiidae, perhaps with reduced cerata and relatively narrow shape so that it is better camouflaged on the hydroid colonies on which it lives. Its internal anatomy is quite interesting as it has developed ducts of the digestive gland in the body wall as well as the cerata. This is unique in aeolids without zooxanthellae symbiosis and I have suggested that this is to replace the digestive gland volume lost when the number of cerata were reduced.

See message below for a discussion on whether P. atra and P. juliae are distinct species, the latter having a white line down the dorsal midline.

• Baba, K. (1955) Opisthobranchia of Sagami Bay. Supplement. Iwanami Shoten, Tokyo.
• Baba, K. (1992) Comment on the taxonomy of Protaeolidiella atra Baba, 1955 and an allied species from Japan. Report of the Sado marine Biological Station, Niigata University, 22: 29-35.
• Rudman, W.B. (1990.) Protaeolidiella atra Baba, 1955 and Pleurolidia juliae Burn, 1966; one species, two families (Nudibranchia). Journal of Molluscan Studies, 56(4): 505-514.

Authorship details
Rudman, W.B., 1999 (April 1) Protaeolidiella atra Baba, 1955. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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