Hypselodoris maridadilus & H. mouaci etc.

March 1, 1999
From: Clay Bryce


You made the mistake of mentioning, when you posted the page on Hypselodoris emma that you would post some info on H. mouaci, Hypselodoris maridadilus and Hypselodoris whitei in the near future. Any chance this email will hurry you along a bit - not that I'm pressuring you but would be really interested to read what you think of H.mouaci vs H. maridadilus.


Clay Bryce
Department of Aquatic Zoology (Molluscs)
Museum of Natural Science
Francis St.
Perth, 6000
W. Australia


Bryce, C., 1999 (Mar 1) Hypselodoris maridadilus & H. mouaci etc.. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/624

Dear Clay,
Your plaintive email jogged me into action.. although I wouldn't say that this will be the final word.

It looks to me that there are a pair of sibling species, one in the Indian Ocean (H. maridadilus) and one in the western Pacific (H. whitei). The major difference would seem to be the white upper (inner)edge to each gill and the white tip to the rhinophore in the western Pacific species. There is some colour variation in the western Pacific with specimens from the northern end of the range, Japan, Hawaii, Enewetak having a very opaque whitish background colour which is replaced further south by a series of opaque white or cream patches on a darker translucent background. I can't find distinctive differences in radular morphology.

Nathalie Yonow described a species, Hypselodoris centunculus from the Maldives in the eastern Indian Ocean. She describes white-tipped rhinophores, which are characteristic of H. whitei, but she describes the gills as orange, which is characteristic of H. marididalus. It is difficult from the accompanying photo to see whether there is a white edging to the upper (inner) edge of the gills, or whether the white tips to the rhinophores are a photographic artifact. At this stage I think we will need to wait for more material, or at least photos, to determine the colour variability across the eastern Indian Ocean. I have posted two pages, Hypselodoris maridadilus and Hypselodoris whitei, one for each geographic region. Any further photos gratefully received.

Bill Rudman.

Rudman, W.B., 1999 (Mar 1). Comment on Hypselodoris maridadilus & H. mouaci etc. by Clay Bryce. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/624

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