Atagema alba

(O’Donoghue, 1927) Photo courtesy of Steve Gardner
La Jolla Shores, San Diego, California

Atagema alba (O’Donoghue, 1927)

Atagema alba is one of those California species that is not seen in years, and then someone comes across a population explosion. This has occurred this year in the San Diego and Channel Islands.

This strange little mouse-like dorid is easily identified by the irregular ridge down the midline and the three large extrabranchial lobes anterior to the gill. The fuzzy appearance of the dorsum is produced by caryophyllidia (tubercles with protruding spicules).

Little is known about the species, but I believe it is a sponge eater, like other Atagemas. It has been documented only from Monterey Bay south to Ensenada, Mexico. It has been collected in Scripps Canyon, San Diego at 120 feet (Jim Lance, pers. comm.).

Nice find Steve.

Dave Behrens
Gig Harbor, Washington
Aug, 2005

Addenda to Atagema alba by Hans Bertsch:

             Atagema alba has been found on the steep cliffs of Arbolitos, Punta Banda, south of Ensenada, Mexico. The walls are brilliantly covered with numerous invertebrates, especially the bright orange cup coral Balanophyllia elegans. The in situ picture of a 38 mm long animal was taken at 45 feet depth, 2 December 1984. I have not seen it since in my southern California/northwestern Baja California water diving. As Dave noted, this rare species ranges from the intertidal to 120 feet deep.

            Dave Mulliner took a portrait photo of this animal , illustrating its distinctive features, especially the lobes protruding posteriorly over the gills.

             The radula is the typical dorid sponge-eating shape, with smooth, curved hamate cusps. Terry Gosliner and I described the radula , anatomy, synonymy and distribution of this species in our 1986 paper.


Bertsch, Hans, and Terrence M. Gosliner. 1986. Anatomy, distribution, synonymy, and systematic relationships of Atagema alba (O’Donoghue, 1927) (Nudibranchia: Doridacea). The Veliger 29 (1): 123-128.

Hans Bertsch is well known to readers of the SlugSite both from underwater and above water activites. This photo of Rosa and him was taken recently on Gatún Lake, Panama, while on their way to visit the Smithsonian Tropical Research Institute preserve on Isla Barro Colorado.

Steve Gardner at La Jolla Shores
Steve uses a Olympus 5050Z in a Ikelite housing with two Ikelite DS 50 strobes.
For branchs, Steve uses Supermacro, F 8, ISO 100, 100/sec on Auto Focus.

Steve has been very active in the San Diego Oceans Foundation's 2005 Dive - a - Thon to raise money. You can help raise $25,000 for the San Diego Oceans Foundation by registering to participate in the 1st Annual Dive-a-Thon! The monies raised will help support our Foundation's ongoing projects and programs that include: Ships to Reefs, Underwater Research, Fisheries Enhancement, Marine Science Education, and pollution prevention programs! You have the opportunity to win AWESOME prizes like scuba equipment, dive trips, restaurant gift certificates, SeaWorld passes and so much more! You have the opportunity to win AWESOME prizes like scuba equipment, dive trips, restaurant gift certificates, SeaWorld passes and so much more! If you cannot participate yourself and want to help me, go to this link and support me or to the web page of the S.D. Oceans Foundation

Send Steve email at

Webmaster's Notes Steve has been on the mend the last few months from knee surgery but is back in the water now at his familiar diving haunts, the shores! I can't think of a more deserving cause or person to contribute to in behalf of!

The Webmaster
San Diego, Calfornia
August 2005

Puerto Vallarta, Mexico
March 2005

Ali Hermosillo and Dave Behrens

Author: Pacific Coast Nudibranchs
Co-Author Coral Reef Animals of the Indo Pacific
Proprietor of Sea Challengers Natural History Books

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