A fairly rare nudibranch to divers because of its association with flotsam and jetsam, the specimen shown here was one of three found ( by George Spalding of the UCSD dive club) hitch hiking on a plastic bag in Scripps Canyon. Referred to as a pelagic branch, this species is always found on floating debris such as logs and kelp rafts which are covered with the pelagic barnacle, Lepas, on which this aeolid feeds. It has also been found on an open ocean, surface dwelling jellyfish, the By-the-wind-sailer, Vellella.
The color of individuals is dependent on their diet, cream to brown when feeding on barnacles, purple when Vellella is eaten. The dorsal surface of this species is clear of cerata which are a unique sailshape (see Behrens, 1991).
Because of its pelagic existence the species is cosmopolitan, found in all northern seas. Unlike othe nudibranchs this species is found only with its food resourse. Its life cycle is quite interesting and far more problematic than other benthic species which can crawl around looking for more food. At the risk of violating the chicken before the egg dilemma, it literally feed until the food is gone, lay eggs, eggs hatch, planktonic larvae ride the currents until the right food is located, and in the middle of the ocean who knows how long that can take, then metamorphose into a juvenile, feed, grow and repeat the cycle again. When found it is often is very large numbers.
The above information courtesy of:
David W. Behrens
Pacific Coast Nudibranchs
Send Dave email at email@example.com