Unknown chromodorid from Brazil

Dear Armando,
If you have more photos of this animal it would be useful as I can't see the gills or the rhinophores clearly, and their colour is often important for identifications. There are a large group of blue chromodorids with white and yellow lines in the Atlantic, and the Mediterranean, and species are often difficult to identify.

In the last major review of these blue chromodorids (Ortea, Valdés & García-Gómez, 1996), a new species, Mexichromis molloi, was described from Venezuela, which is quite similar to your species. The mantle is blue with a white median line, and there is an orange-yellow mantle border, inside of which is a dark blue band and then a white band. The gills and rhinophores are blue and there is a single white line along each side of the blue body.

However your animal matches almost exactly Kempf's sketches of Mexichromis kempfi (Marcus, 1970), which I have copied alongside. What I can't see in your photo is the colour of the foot. If you have another photo or a memory of the foot colour I would be interested to know. If your animal is M. kempfi, the other animals I have identified on the Forum as this species seem rather different but I am pretty sure they are the same species. The major difference is that the lighter blue mantle colour present in your photo, is often absent. However in Phanor Montoya's photos from Colombia [#3209] the pale animals have a dark blue foot. Interestingly, they also show traces of the white line on each side of the foot, which is described for Mexichromis molloi, and suggests that it may in fact be another colour form of M. kempfi. Marcus described M. kempfi from the north coast of Brazil, so your photo extends the known range of the species further south. It is a very useful addition to the Forum as it is the first photo I have seen which matches Kempf's original sketch so accurately.

• Marcus, E. (1970) Opisthobranchs from northern Brazil. Bulletin of Marine Science, 24: 922-951.
• Ortea, J., Valdés, A. & and 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