Thorunna florens-Color variation

November 11, 1998
From: Rebecca Johnson

5 November 1998
Dear Dr. Rudman,
As you know, I am working on the genus Thorunna and of the other small chromodorid genera. I recently received a photo of an animal from Bali that I think may be T.florens(unfortuately there is no specimen). I have your specimen of T. florens from Thailand C.162380 and its radula is quite different from either of the T.florens radulae you have published. This animal has an inner lateral tooth that is shorter and more curved than any of the other lateral teeth, more like T. africana. The animal from Bali is very similar in color to the animal from Hong Kong pictured in your 1990 paper on the C. aureomarginata color group, except it is much brighter in color and has red rhinophores and gills. I was hoping you could post a photo of T. florens from Thailand to help me figure out what I am looking at. I can probably post photos from Bali and the radula if it would be of interest to you.
Thank you very much.
Rebecca Johnson

Johnson, R., 1998 (Nov 11) Thorunna florens-Color variation. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Rebecca,
I have posted, at the top of this page, photos of the three colour "forms" of Thorunna florens including the one from Thailand you were inquiring about.

The Hong Kong colour form matches the "typical" Japanese specimens well, differing only to the extent that the purple submarginal line is broken up into a string of blotches in most reported Japanese specimens. At this stage I feel the Western Australian specimens have a colour pattern which can easily be derived from the Japanese pattern. In internal anatomy, including radular morphology, the Hong Kong and Western Australian specimens matched the Japanese material.

Concerning the Thailand specimen which you say has a differently shaped first lateral tooth. Until your message I had assumed that it was T. florens because the colour pattern was very similar to Japanese material, apart from the yellow lines being replaced by broader orange bands. One feature of T. florens appears to be the broad orange or yellow band around the anterior end of the mantle. This is present in the Thai specimen although it is difficult to see because the front of the mantle is damaged.

From memory, only two other species of Thorunna have broad orange red anterior mantle bands. By coincidence both are already illustrated in the Forum: Thorunna montrouzieri and Thorunna speciosus . Another species which looks something like the Thai specimen is Thorunna australis which I have just posted a picture of.

This doesn't solve the problem of the aberrant-toothed Thai specimen. I'm afraid I had only one specimen so there is little we can do but wait until more material turns up. Perhaps it represents a consistently distinct species, or perhaps it has an aberrant radula.

Concerning the Bali photo and the radula photo. I would very much like to see them and to include them in the Forum.

Best wishes
Bill Rudman.

Rudman, W.B., 1998 (Nov 11). Comment on Thorunna florens-Color variation by Rebecca Johnson. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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