Risbecia ghardaqana from Hurghada, Egypt

October 16, 2007
From: Greg Brown

Concerning message #20755:

Hi Bill,
I've been reading the notes and doubts expressed about Risbecia ghardaqana and thought you might like to see a specimen I collected near the type locality whilst working at the Hurghada marine laboratory in 1980. I always took it to be a good match to Gohar & Aboul-Ela's described species although I also found the more common multi-gilled R. pulchella on the same reef within a few hours.
I've attached my photos of the two forms: Upper & middle photos - R. ghardaqana. Lower photo - R. pulchella.

Locality: Hurghada Marine Lab reef front, 10 m, Egypt, Red Sea, 08 April 1980, In daylight on reef rubble . Length: 48 mm. Photographer: Greg Brown (lab photos).



Brown, G.H., 2007 (Oct 16) Risbecia ghardaqana from Hurghada, Egypt. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20912

Dear Greg,
Thanks very much for these photos. This is the first photo I have seen of a yellow-spotted chromodorid which matches the original description of R. ghardaqana well. Important features are the small number of simple gills and the lack of any purple background 'smudges' on the mantle.

Since Gohar & Aboul-Ela (1957) discovered the new species while studying the embryological development of large populations of the similarly coloured C. annulata and C. pulchella, I have been puzzled by our inability to find it. Apparently it is must be quite rare, or at least rarely found. It was initially considered a species of Chromodoris, and externally it could easily belong to that genus, but its reproductive system, and the little we know of its radula and jawplates, suggest it is a species of Risbecia. We know nothing of the feeding behaviour of these three yellow-spotted species. It would be good to get photos of them feeding, to see if their choice of sponge matches what we know of their generic relationships.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Oct 16). Comment on Risbecia ghardaqana from Hurghada, Egypt by Greg Brown. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20912

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