Rostanga risbeci and R. atrata

Dear Nishina,
Risbec (1953) described a black dorid from New Caledonia which in all aspects of its external and internal anatomy would appear to be a species of Rostanga. He identified it with Doris atrata Kelaart and named it Rostanga atrata Kelaart. However as I have discussed previously (Rudman & Avern, 1989) Kelaart's species was not a species of Rostanga. Kelaart's species from Ceylon [Sri Lanka] was described as pure black with white tips to the rhinophores. No illustrations were published but Eliot (1906b, c) in his report on a re-examination of Kelaart's specimens and illustrations considers it to be synonymous with Dendrodoris nigra Stimpson.

It is difficult to identify Risbec's species with any described species but it could be Rostanga risbeci As Risbec's name Rostanga atrata is simply a misidentification it has no taxonomic status. Until further material is available from New Caledonia the identity of Risbec's species will be a mystery. Dr Baba wrote to me about his black Rostanga when he was preparing his paper. My feeling was that the shape of the radular teeth suggested it might be a black colour form of Rostanga dentacus, but we will need to examine more specimens and look at their natural history - egg ribbons, food sponges etc., before we can be sure one way or the other.

I am at the moment preparing some "Fact Sheets" on all the species of Rostanga. One problem with studying them is that they are difficult to identify alive because they are so similar in shape and colour. That is why I keep asking for information on egg ribbons and food sponges because we do know that these can be very useful identification tools.

• Rudman, W.B., Avern, G. (1989) The genus Rostanga (Nudibranchia: Dorididae) in the Indo-West Pacific. Zoological Journal of the Linnean Society, 96(3): 281-338.

Best wishes,
Bill Rudman