Hypselodoris bilineata? from Senegal

Dear Valerie & Marina,
I agree these are very interesting animals. I think they also illustrate that we still have a lot to learn about the Atlantic 'blue chromodorids'. They certainly have similarities in colour to H. bilineata, but the distinctive feature in that species seems to be the median double yellow line on the dorsum. Edmunds (1982) identifies animals from Ghana, with white lines inside the yellow lines as H. bilineata, and Ortea et al (1996) do the same with animals from Senegal. In the animals in your message there are no median yellow lines, although there is a single median row of yellow dots in one animal. Instead the prominent feature are the fine yellow dots scattered all over the central part of the mantle and the sides of the body. 

I don't know if you have a copy of Ortea et al (1996), but although I am puzzled by some of the decisions in that revision, it is the best summary available. In that they have a photo (Fig 7E) of a juvenile of H. malacitana which has the same basic colour pattern as your animals, although the spots are a little larger.

I am posting a number of messages today on 'blue chromodorids'. I hope some local experts can give us their opinions.

• Edmunds, M. (1981) Opisthobranchiate Mollusca from Ghana: Chromodorididae. Zoological Journal of the Linnean Society, 72(2): 175-201.
• Ortea, J., Valdés, A. & García-Gómez, J.C. (1996) Revisión de las especies atlánticas de la familia Chromodorididae (Mollusca: Nudibranchia) de grupo cromático azul. [Review of the Atlantic species of the family Chromodorididae (Mollusca: Nudibranchia) of the blue chromatic group.] Avicennia, 1996, Suppl. 1: 1-165.

Best wishes,
Bill Rudman