Thai fried egg nudibranch?

March 16, 2005
From: Alyson Browett

I learned about nudibranchs from a couple I met on my way home from Costa Rica in 2002 -- too late to search for them while diving.

However, while in Koh Tao, Thailand, in mid-July 2004, I spotted two at about 10-15 meters depth. Koh Tao is in the Gulf of Thailand, and we were about 200 meters from shore. My husband, trying out underwater photography for the first time, got a minimally recognizable shot (attached).

I began calling them fried egg nudibranchs without knowing anything about them. I just came across your site while searching for information on nudibranchs, and I have to say that this is one of the best sites on the Web (and I design information Web sites for a living).

Locality: Koh Tao, Thailand, Gulf of Thailand. Depth: 10-15 meters. Length: large: 6 in. small: 3 in. 21 July 2004 reef. Photographer: John Ralph

I'm interested in knowing any more information about my fried egg nudibranchs!

Alyson Browett
Purcellville, VA, USA

Browett, A.M., 2005 (Mar 16) Thai fried egg nudibranch?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Alyson,
Your two animals are phyllidiid nudibranchs - and both have a 'fried egg' colour pattern.. The larger is Phyllidia varicosa and the smaller one is, I think, Fryeria menindie. You can find more about the individual species on their respective Fact Sheets and accompanying messages. One interesting point your photo illustrates is that during the day, the phyllidiids are almost the only sea slugs which show themselves out on the reef. They are well protected from possible fish attack by very noxious chemicals they store in small glands in their skin, which they obtain from the sponges they feed on. There is a whole field of natural products chemistry which has built up to study the way animals have evolved the ability to make defensive chemicals and for others to steal them for re-use. The impetus for the research is not so much because of an seoteric interest in this field of evolution, but because these powerful molecules may turn out to cure some nasty human ailment.

Glad you like the site. We are in the middle of an upgrade at the moment - hopefully when I get some time I will put in some guides to make it easier for novices to do some self identification - or at least get down to a family grouping.
Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Mar 16). Comment on Thai fried egg nudibranch? by Alyson Browett. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Phyllidia varicosa

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