Risbecia ghardaqana from Oman

October 30, 2000
From: Gordon T. Smith

Dear Bill,

I have been diving the north part of Oman (Musandam)[NW Indian Ocean] recently fairly frequently with practically no sightings of nudibranchs until recently.

I found a pair mating three days ago, please see attached photo [UPPER PHOTO].

I would like to confirm identification as Risbecia pulchella, however they did look more like Chromodoris annulata without the purple rings around the gills and rhinophores.

I have included a photo of a pair of Risbecia pulchella that I photographed near Muscat (Oman) 2 years ago.
Gordon T. Smith


Smith, G.T., 2000 (Oct 30) Risbecia ghardaqana from Oman. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3256

Dear Gordon,
This is an interesting find. In the western Indian Ocean there are at least three similarly coloured yellow-spotted chromodorids, two of which you mention in your message. Both those species have quite a wide Indian Ocean distribution, but the third, Risbecia ghardaqana is known only from the Red Sea. While I agree that the pair of animals in your lower photo from Muscat are R. pulchella, I suspect the mating pair from Musandam are Risbecia ghardaqana.
The yellow spots seem to be a bit small for R. ghardaqana but they are proportionally quite a bit larger and less densely spaced than in R. pulchella.

I would be interested in seeing a photo of the foot, if you have one, to see if it has a purple border. I would also like to know if you remember if the gills wriggled rhythmically as the animal crawled along. As with any photos you send to the Forum, I would be interested in some idea of size. As I am about to leave for a month's collecting, I will not be able to respond to any reply immediately, but anything you send will not be lost. It will just sit waiting patiently for my return. Good luck with sea slug hunting in Oman. There is little known from the region and any information and photos would be welcome.
Best wishes,
Bill Rudman.

Rudman, W.B., 2000 (Oct 30). Comment on Risbecia ghardaqana from Oman by Gordon T. Smith. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3256

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