Melanistic Chromodoris hamiltoni is H. regina

January 11, 2007
From: Bill Rudman

Concerning message #18677:

I have been puzzling over this identification for some time. I was pretty sure it was Chromodoris hamiltoni but if it was a Chromodoris the sponge the animals are clearly eating is a problem. It is a species of Dysidea, a genus of sponges which is not normally eaten by species of Chromodoris. On the other hand, it has similarities in colour to Hypselodoris regina and Erwin Koehler has sent photos [message #13953 ] of a quite similar looking pair of animals which I had previously identified as H. regina. In Erwin's photos they are feeding on the same sponge, a genus commonly eaten by species of Hypselodoris.

Although I would need to look at the anatomy to be certain, it seems as though these animals are a colour variation on Hypselodoris regina Interestingly, the only reference I have to feeding in C. hamiltoni is to it feeding on a species of Negombata [ as Latrunculia sp], a red sponge similar in appearance to the red sponges in the upper half of the photo (Pika & Faulkner, 1995). If it weren't for the everted buccal bulb of one of these animals on to the bluish Dysidea I would have considered this photo to be too ambiguous to identify either the nudibranch or the sponge.

• Pika, J. & Faulkner, D. J. 1995. Unusual chlorinated Homo-Diterpenes from the South African nudibranch Chromodoris hamiltoni. Tetrahedron, 51: 8189-8198.

Bill Rudman

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