Is Ceratosoma magnifica (Eliot, 1910) a good species?

April 30, 2007
From: Bill Rudman

There has been a history of confusion surrounding the genera Miamira Bergh, 1875, Orodoris Bergh, 1875, Fracassa Bergh, 1878 and their included species. Some of the history of this is outlined in Valdes & Gosliner (1999) who proposed that this group are species of the chromodorid genus Ceratosoma. In their study they examined Ceratosoma miamirana [= Orodoris miamirana Bergh, 1875; Fracassa tuberculosa Eliot, 1903] and Ceratosoma sinuata [= Doris sinuata van Hasselt, 1824; Miamira nobilis Bergh, 1875].

PAINTINGS: Miamira magnifica: original illustrations from Eliot, 1910: Pl. 25.

Unfortunately they did not examine specimens of two other putative species, Miamira magnifica Eliot, 1910 and Miamira flavicostata Baba, 1940. Following Baba & Hamatani (1974), I have until now on the Forum considered all the various coloured forms of 'Miamira' to be part of one variable species [see message #19853] but the persistent use of the name 'Miamira magnifica' and 'Ceratosoma magnifica' in colour picture books is causing widespread confusion.

There is now a considerable number of records of the 'Miamira' group on the Forum and from those we can see there are two main groups. In one of these the background colour of the animals ranges from bright green to dull purplish brown and the whole body is covered with low rounded yellowish tubercles. Both the gills and the rhinophores are translucent greenish or brownish - depending on the background colour - and have scattered white spots. The anterior end of the mantle is trilobed with the central lobe being much longer than the other two. This colour form fits the original description of Ceratosoma sinuata very well and there can be no doubt of its identity.

The second colour form usually has a broad whitish margin to the mantle, the rest of the mantle being a reddish brown to bright purple with orange rounded ridges. The rhinophores usually lack white markings, but the gills are edged with opaque white lines. The front of the mantle does not have a prominent central lobe. This colour form fits the original description of Miamira flavicostata Baba, 1940. In many popular photo books the name Miamira magnifica or Ceratosoma magnifica is used for this purplish species.  

What is Miamira magnifica Eliot, 1910?  Unfortunately, like so many early descriptions it was based on a single preserved specimen. It was trawled off the Seychelles, and as Eliot notes 'this description was taken from the preserved animal some time after the colour drawing was made'. In the description he mentions greens and purples and white spots, but we have no idea whether these colours represent the live animal or are the result of the real pigments reacting to preservatives. If the greens are real colours then this would have to be C. sinuata because C. flavicostata does not have green coloration, but from the original drawings we can see that the mantle has a pattern of rounded tubercles and some short ridges. Eliot does note that the oral tube is a 'beautiful purple colour' and the rachis of the gills is a yellowish white, making 'a vivid contrast of colours' which may suggest C. flavicostata but we have little to go on.

Some authors have compared the number of radular teeth with animal length but these seem to have all been done with preserved animals. As specimens can shrink to half their living length in preservative, such comparisons based on so few specimens, seems valueless at present. Consideration has also been given to the size and number of the medio-dorsal mantle tubercles, but again these appear to be variable, some specimens having very low bumps and others very prominent erect horns.

From the available information it would seem there are at least two species in this group, one with rounded tubercles and white spots on the gills and rhinophores which we can identify with C. sinuata, and another species with a ridged pattern and distinctive white lines on the gills which can be identified as Baba's M. flavicostata - more appropriately known as Ceratosoma flavicostata. Eliot's description fits neither of these species well.

Is it possible that Eliot's M. magnifica is a third species? At present we have no record of a living 'flavicostata'- like animal from the western Indian Ocean, where M. magnifica was found. However there are three records on the Forum of 'sinuata'-like animals with yellow lines on the rhinophore clubs, one from South Africa [#2147] with white edged gills and two from the Red Sea [#13210, #6822] with red edged gills. Perhaps this is Eliot's species? At present I am recognising C. sinuata and C. flavicostata, because they are identifiable, and tentatively recognising C. magnifica for the few anomolous western Indian Ocean animals I mention above.

• Baba, K. (1940)  Miamira flavicostata n.sp., a nudibranchiate mollusc from Amakusa, Japan. Zoological Magazine, Japan 52(6), 239-240.
• Baba, K & Hamatani, I. (1974) On the synonymy of Miamira sinuata (van Hasselt, 1824) from Japan (Nudibranchia: Dorididae: Miamirinae). Venus, The Japanese Journal of Malacology 33 (2, August), 81-84.
• Eliot, C.N.E. (1910) Nudibranchs collected by Mr. Stanley Gardiner from the Indian Ocean in H.M.S. Sealark. Reports of the Percy Salden Trust Expedition to the Indian Ocean in 1905, under the leadership of Mr. J. Stanley Gardiner, M.A. Transactions of the Linnean Society, Zoology, series 2, 13(2), 411-439, Pl. 25.
• Valdes, A. & Gosliner, T. (1999) Reassessment of the systematic status of Miamira Bergh, 1875 and Orodoris Bergh, 1875 (Nudibranchia; Chromodorididae) in light of phylogenetic analysis. Journal of Molluscan Studies, 65:33-45.

Bill Rudman

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