Ceratosoma flavicostatum
(Baba, 1940)

Order: NUDIBRANCHIA
Suborder: DORIDINA
Superfamily: EUDORIDOIDEA
Family: Chromodorididae

DISTRIBUTION

Western Pacific

PHOTO

Upper: Coffs Harbour region, northern New South Wales, November 1990. AM C164521. Lower: Jibbon Head, Port Hacking, Sydney, NSW, Nov. 1981. Photos: Bill Rudman.

Note added 4 July 2007: The name is changed today from C. flavicostata to C. flavicostatum - see message #20101.

This species has often been identified as Miamira magnificum Eliot, 1910, but there is considerable confusion surrounding the identity of that species. Until now I have, like Baba & Hamatani (1974), considered all the various coloured forms of 'Miamira' to be part of one variable species of Ceratosoma [see message #19853]. As outlined in a separate message [#19854] I am now recognising Ceratosoma sinuatum and Ceratosoma flavicostatum as separate species, and separating a few western Indian Ocean animals as possible specimens of C. magnificum.

Ceratosoma flavicostatum usually has a broad whitish margin to the mantle and the rest of the mantle is a reddish brown or even 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. In both this species and C. sinuatum there can be up to three large tubercles in the dorsal midline between the gills and the rhinophores. If present, the most posterior one, just in front of the gills, is the longest, often standing much taller than the gills.

C. flavicostatum was first described from Japan and has been reported since from many parts of the tropical western Pacific. The name flavicostatum [= yellow ridges] indicates one of the most obvious characters of this species.

• 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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