Secondly, not having the benefit of the defensive cnidosac found in other aeolids,Phyllodesmium magnum is an example of a species that displays "autotomy" or the defensive behavior of casting off its cerata when attacked or disturbed. The autotomization of tissue or body parts is best recalled in lizards, who loose their tail when tugged on, brittle stars who drop the legs to facilitate rapid escape and other nudibranch species like Melibe, who cast off their cerata, and swim away leaving the cloud of cerata for the challenger. In Phyllodesmium magnum, the autotomised cerata produce a sticky epithelial secretion and wriggle around vigorously for a considerable length of time after dropping off, apparently causing sufficient distraction to deter further interest in the now even more naked nudibranch. See Bill Rudman's Sea Slug forum , for details.
Phyllodesmium magnum feeds on several octocoral species including
Sinularia, Sarcophyton and as seen in Mike's photo, Cespitularia. It is
widely distributed throughout the Indo-Pacific, with documented
observations from Tanzania, Australia, New Guinea, Indonesia, the
Philippines, New Caledonia, Hong Kong, Guam, Enewetak and Japan.
References of interest:
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.
Taxonomic information courtesy of Dave Behrens
David W. Behrens
Pacific Coast Nudibranchs
Send Dave mail at firstname.lastname@example.org