Roboastra gracilis
(Bergh, 1877)

Order: NUDIBRANCHIA
Suborder: DORIDINA
Superfamily: ANADORIDOIDEA
Family: Polyceridae
Subfamily: Nembrothinae

DISTRIBUTION

Tropical West Pacific.

PHOTO

Lizard Is, North Queensland, Great Barrier Reef, June 1979. Lower photo showing large enrolled oral tentacles. PHOTOS: Bill Rudman.

Relatively small nembrothid, growing to about 20-25mm in length. Characterised by the yellow longitudinal lines which are sometimes quite onscure. These lines consist of a series of glandular pits which secrete a bright yellow substance when disturbed. Although I have no feeding records this species is a member of a genus which hunts down and eats other opisthobranchs. The large oral tentacles (arrowed) are found in all members of Roboastra and are probably important in tracking down their prey, perhaps by following its mucus trail.

Reference:
• Bergh, L.S.R. (1877). Malacologische Untersuchungen. In: C.G. Semper, Reisen im Archipel der Philippinen, Wissenschaftliche Resultate. Band 2, Heft 11: 429-494, Pls. 54-57.

Authorship details
Rudman, W.B., 2000 (July 17) Roboastra gracilis (Bergh, 1877). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/robograc

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