Mexichromis multituberculata? from Oman?

Dear Darja,
The pointed tubercles on the mantle are similar to those of some Cadlinella, but this is a species of Mexichromis, and almost certainly the one we are calling Mexichromis multituberculata. However the more photos I see of this 'species' the more I wonder whether there is one variable species ranging in colour from purple to reddish spots and ranging in the degree the spots became raised into rounded tubercles and even pointed tubercles. When I first tried to identify a specimen of this purple spotted form [from India - Rudman, 1973] I concluded it was a form of C. mariei (Crosse, 1872) first described from New Caledonia. Until recently I have been happy to accept Baba's name M. multituberculata for animals with large pointed tubercles on the mantle, but the variability shown in photos on the Forum which I have variously identified as M. mariei, M. cf. mariei. M. multituberculata and M. cf. multituberculata make me wonder if they are all variations of one species. Even M. festiva and M. macropus are very similar [see Rudman, 1983].

If this form with pointed tubercles is considered distinct the Chromodoris sannio Bergh, 1890 is a much earlier name. It was described from Indonesia and the purple spots were described as being raised on vesicles. Charles Eliot (1905) reported similar animals from Muscat 100 years ago and identified them as C. sannio. So what should you call your animals? I would suggest you use Mexichromis multituberculata, but I suspect when this group is sorted out we will use M. mariei for them all, or perhaps M. sannio for the pointed ones.

If this species is quite common in your area, it would be worthwhile keeping a lookout for variability in colour and whether the spots vary from rounded tubercles to pointed papillae. If we are dealing with a variable species it would be nice to get some evidence of it in local populations.

• Bergh, L. S. R. (1890) Die Nudibranchien des "Sunda-Meeres". Malacologische Untersuchungen. In: C.G. Semper, Reisen im Archipel der Philippinen, Wissenschaftliche Resultate., 17, 873-992,Pls.885-889.
• Crosse, J. C. H. (1872) Description d'un genre nouveau et d'espèces inédite, provenant de la Nouvelle-Calédonie. Journal de Conchyliologie, 20, 148-154.
• Eliot, C. N. E. (1905) Nudibranchs from the Indo-Pacific. 1. Notes on a collection dredged near Karachi and Maskat. Journal of Conchology, 11, 237-256.
• Rudman, W. B. (1973) Chromodorid opisthobranch Mollusca from the Indo-West Pacific. Zoological Journal of the Linnean Society, 52, 175-199,177figs,172col.pl.
• Rudman, W. B. (1983) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris splendida, C. aspersa and Hypselodoris placida colour groups. Zoological Journal of the Linnean Society, 78, 105-173.

Best wishes,
Bill Rudman