Variation? in Chromodoris dianae

June 25, 2001
From: Bernard Picton

Hi Bill,
These Chromodoris dianae are a small selection of the ones I have seen over the years. I have my doubts as to whether it is one variable species. While the gills in 'true' C. dianae are variable in colour and the orange pigment spots at the edge of the mantle develop from nowhere in slightly larger individuals, the form with white gill bases abruptly changing to yellow tips seems different. There are other features which distinguish it from C dianae in my opinion. I'll call it C. cf. dianae in this message for clarity. In C. cf. dianae the whitish pigment all over the mantle is not areolate as it is in C. dianae and has a different 'consistency'. There is normally a black curved line across the front of the head and a circular black spot between the rhinophores, whilst in C. dianae there is a line of black spots which develop in the midline of the back and between the rhinophores - predominantly longitudinal rather than the transverse sort of marking in C. cf. dianae. C. cf. dianae also seems to be a broader animal even given the way nudibranchs change shape as they move.

I've re-read Dave and Terry's paper and I still think there are two entities here as you suggested in an earlier message. (I don't agree completely with the way you divided Lindsay's pictures! Only the first one from Hoga is definitely C. cf. dianae by my criteria and is probably the same individual as my chrdia3. This is a tricky problem, is anyone looking at DNA or enzymes?

My pictures as follows -
chrdia - Hoga, Indonesia, 1997
chrdia1 - Hoga, Indonesia, 1997
chrdia2 - Sipadan, Malaysia - 1992
chrdia3 - Hoga, Indonesia, 1997 - C. cf. dianae
chrdia4 - Bali - 1996 - C. cf. dianae
chrdia5 - Sipadan, Malaysia - 1992
chrdia6 - Philippines, 1983


Picton, B.E., 2001 (Jun 25) Variation? in Chromodoris dianae. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Bernard,
There's nothing like a good taxonomic tangle to stir the blood! Two questions arise if it turns out that there is more than one species. The first is: Which is the real C. dianae? - there is nothing in the original description to identify the colour form of the holotype. The second question is that if the variable form (not the yellow-tipped gill form) is the 'real' C. dianae, then how does it differ from some of the colour forms of Chromodoris michaeli in yesterday's message?

Best wishes,
Bill Rudman.

Rudman, W.B., 2001 (Jun 25). Comment on Variation? in Chromodoris dianae by Bernard Picton. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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