Acanthodoris rhodoceras

Photo taken at Catalina Island (California)
Photo courtesy of Elaine Jobin

Acanthodoris rhodoceras Cockerell and Eliot, 1905

Acanthodoris rhodoceras Cockerell and Eliot, 1905

Theodore Dru Alison Cockerell and Charles Norton Edgecombe Eliot chose the trivial name "rhodoceras" to call attention to this species red tipped rhinophores, "rhodoceras" meaning red horn. Originally described from San Pedro, California, the species geographic range now extends into the Gulf of California to Bahia de los Angeles, and north to the mouth of the Umpqua River in Oregon.

Like other members of the genus the dorsum is covered with tall pointed papillations. Its ground color is white, with a yellow marginal band followed by a black band. The gill and rhinophores are tipped in black. The rhinophores have a very distinctive opaque white line running up the posterior, to the red region, clearly seen in Elaine’s photo above.

Elaine’s specimen is an example of the color phase without black on the dorsal papillations. Often, specimens will have numerous, random papillations tipped in solid black as if dipped into ink. See also an image taken at La Jolla Shores, San Diego, California by SDUPS photographer Tracy Clark which is also illustrative of this color variation in addition to displaying A. rhodoceras's egg mass

Members of this genus feed on bryozoans, and Acanthodoris rhodoceras is reported to feed specifically on Alcyonidium sp.

Dave Behrens
Danville, Calif
Feb.. 2005

I have been diving for about 15 years and have been fascinated with underwater photography from the start. I am fortunate to live in Southern California and I dive locally at least once a week. I work as a Certified Registered Nurse Anesthetist to support my hobby.

Some of my most treasured moments are from the weeks, and probably months, which I spent with Jim or Cathy Church learning as much as I could about underwater photography. I have won awards from the Northern California Underwater Photographic Society, PADI project aware, the Coral Reef Alliance, and the California Department of Fish and Game. As a member of the Catalina Conservancy Divers I have helped to collect island research data, and, as far as I can tell I was the first girl to be the site leader for the Conservancy sponsored Casino Point Scuba Trail. I write regular “trip reports” for which include photos of my diving adventures. I use my trip reports to share as much of the ocean world as I can with others.

I have a Sea&Sea Housed Nikon F100, several Nikonos V’s, and an overworked slide scanner. I frequently take up to three camera set ups with me when I go out for a day of diving. That is, in part, why I had the “right lens” to capture this dorid with my Nikonos V while diving from one of our local dive boats, the Sundiver, this past weekend.

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Taxonomic information courtesy of:

David W. 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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