Dermatobranchus gonatophora belongs to the nudibranch group referred to as Arminacea. This unnatural group has been referred to as many things by cynical taxonomists, I just call it the sea slugs lovers catch all for those species, which for the absence of certain significant taxonomic features get dubbed - "not any of the above." The only character that really united this desperate group is the presence of an oral veil. This group is in real need of a serious make over.
The Indo-Pacific seems to be the hot spot for arminid diversity, providing the home for many species. Two similar genera, within which this species resides are Armina and Dermatobranchus. Both are characterized by a series of longitudinal ridges on the dorsal surface.
Debelius in Nudibranchs and Sea Snails(1996) presents a dramatic collection of examples of these genera, including photos of two color phases of D. gonatophora(Page 295). Dave Mulliner's photo shown here (which also appeared in Coral Reef Animal of the Indo-Pacific, species # 617) is the more typical color of this species, which does display some variation.
Of particular note in Dave's photograph, is that this specimen is seen attacking one of its prey species, the soft coral, Eleutherobia grayi (see Coral Reef Animal of the Indo-Pacific, species # 73). Dermatobranchs also feed on penatulaceans (sea pens), usually on sand or coral rubble bottoms.
The large species, measuring up to 12 cm in length, has a wide distribution, which includes Okinawa (location of this photo), Indonesia, Thailand and recently, the Red Sea.
The Slug Site would like to acknowledge Dr. Bob Bolland in Okinawa and the The Okinawa Slug Site for making this weeks BOW possible. For those who haven't visited Bob's site, you are indeed missing out on one of the net's premier slug sites!! Dermatobranchus gonatophora was run previously on the Okinawa Slug Site and is well worth revisiting!!
David W. Behrens
Pacific Coast Nudibranchs
Send Dave mail at firstname.lastname@example.org