Re: Hypselodoris acriba or H. bayeri?

August 31, 2009
From: Wayne Atkinson

Concerning message #16899:

Dear Bill,
Further to Valda Bromfield's and Eveline Marcus' photos of Hypselodoris bayeri from the Virgin Islands I attach a couple of shots of the same animal, again from the Virgin islands. It seems this colour morph (if that is what it is) with the lines around the mantle is the norm here - I hope these are useful/of interest.

Locality: Mercurious Rock, 12 metres, Jost Van Dyke, BVI, Caribbean Sea, 28 August 2009, rock reef. Length: 2 inches. Photographer: Wayne Atkinson.

Wayne Atkinson

Atkinson, W.L., 2009 (Aug 31) Re: Hypselodoris acriba or H. bayeri?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Wayne,

More photos of these puzzling caribbean chromodorids are always welcome. Although photos alone will not resolve the puzzles, I have found them extremely valuable in the past when you are trying to formulate the question to ask. For example can the animals I am calling H. acriba and H. bayeri on the Forum be just colour forms of one species. And is the animal in Lureen Ferretti's recent message [#22617] also a colour form? One problem is that some of the existing species were not well described, and another problem is that species of Hypselodoris and Chromodoris are well-known mimics, with groups of similarly coloured species evolving in the same geographic region. As I mentioned earlier, [message #7999], Eveline Marcus considered your animal to be a colour form of  H. bayeri, while in Carribean Sea Slugs it is considered a possible form of H. acriba.

Your animal could well be associated with the bright blue sponge in  your photos - which I suspect is a species of Dysidea. Interestingly this is the same sponge which is illustrated in Carribean Sea Slugs as the food of Hypselodoris sp. 3 - which I suspect is part of the H. bayeri complex. However most species of Hypselodoris feed on dysideid sponges so we can't make too much of them feeding on the same sponge.

Sorting out problems like this can't be done in an a chair 1000s of km away. I suspect what is needed is a local research worker who is able to study populations over a number of years, and record colour variability, study anatomy and biology and has the help of dedicated amateurs who can make extra collections and observations. Visiting researchers, no matter how skilled, can only collect small samples in place and time, and as we can see from the present situation, this can lead to confusion rather than clarification.

  • Valdes, A., Hamann, J., Behrens, D.W. & DuPont, A. 2006. Caribbean Sea Slugs. Sea Challengers.

 Best wishes,
Bill Rudman

Rudman, W.B., 2009 (Aug 31). Comment on Re: Hypselodoris acriba or H. bayeri? by Wayne Atkinson. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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