Mexichromis multituberculata or M. katalexis?

Dear Philibert,

As you will see in earlier messages [#8655], my feeling is that Mexichromis multituberculata encompasses colour forms with orange and wine red mantle borders as well as the typical blue border. Nathalie Yonow's Mexichromis katalexis, with orange spots around the mantle border and wine red-tipped tubercles would seem to be part of the colour variation within this species. Yonow (2001) considers there are radular differences - the first two laterals are not as flattened as the other laterals - but she only had glass slide mounts of the radula so such differences could be as much to do with the thickness of the mounting medium as any real morphological difference.

We now have a lot of photos on the Forum showing colour variability in this group of the genus. I don't think there is much to be gained in pulling out one colour form and giving it a new species name. Your animal shows the problems in thinking that way. If we accept M. katalexis with red tipped tubercles and orange-yellow patches around the mantle border, we would have to make a new species for your animal with blue-tipped tubercles and an almost continuous yellow line around the edge of the border, and another for the form with red tips and red border etc, etc.

• Yonow, N. (2001) Results of the Rumphius Biohistorical Expedition to Ambon (1990). Part 11. Doridacea of the families Chromodorididae and Hexabranchidae (Mollusca, Gastropoda, Opisthobranchia, Nudibranchia), including additional Moluccan material. Zoologische Mededelingen uitgegeven Rijks Museum van Natuurlijke Historie te Leiden 75: 1-50.

Best wishes,
Bill Rudman