Identity of Chromodoris decora

September 14, 2007
From: Bill Rudman

Upper: Chromodoris decora [from Bergh, 1880: Plate B, fig 5]. Lower left: Chromodoris lentiginosa [from Pease, 1871: Plate 9, fig 1]. Lower right: Chromodoris ndukuei [from Risbec, 1928: Plate VI, fig 2].

Scott Johnson's recent messages [#20696, #20697] on the identity of Chromodoris decora have caused me to actually prepare a description for the Fact Sheet - which until now included only photos - and to post these scans of illustrations from early descriptions of this species and some other species which I consider synonyms.

Pease's description of Doris decora did not include an illustration but as I discuss in Scott Johnson's message with photos of Hawaiian specimens [#20697], his upper photo matches Pease's written description almost exactly:
"Dorsal region pale straw-colour, with a medial whitish longitudinal stripe, which is bifurcated posteriorly and dotted with purple. The margin of the mantle is bordered with white and dotted with purple; an intramarginal light red band, contiguous with a yellow one, which is dotted with purple ...."

I have included a scan of Bergh's (1880) illustration of Chromodoris decora as I am pretty sure it was seen by Pease. Both Pease and Bergh used material collected and painted by Andrew Garrett. As I have discussed elsewhere this dual arrangement sometimes led to confusion with both Pease in Hawaii and Bergh in Europe describing the same species [same specimens? illustrations?] with different names [see #1852 ]. In this case however Bergh has acknowledged Pease's name for the species.

Pease (1871) later described Chromodoris lentiginosa from Tahiti, which appears to be a specimen of the C. decora in which the bifurcating white line is not entire. He describes the 'median interrupted cream coloured stripe in which are disposed purple spots.... '.

Another name is Chromodoris ndukuei  Risbec, 1928, which surely represents an animal in which the white Y shaped median line has multiple branches. It looks very like the upper photo in Scottt Johnson's feeding photo in message #20701.

The other name, which I haven't illustrated is Chromodoris setoensis Baba, 1938 which is the colour form in which the Y-shape white line lacks purple spots. Baba himself (1953) suggested it should be considered a synonym of C. decora. I may be wrong, but all these forms seem to represent variations of one species. The most distinctive features of the pattern are the white line that encircles the gills and rhinophores and the the median line which bifurcates.

• Baba, K. (1938) Opisthobranchia of Kii, Middle Japan. Journal of the Department of Agriculture. Kyusyu Imperial University, 6(1): 1-19.
• Baba, K. (1953) Three new species and two new records of the genus Glossodoris from Japan. Publications of the Seto Marine Biological Laboratory 3(2): 205-211.
• Bergh, L.S.R. (1880): Malacologische Untersuchungen. In: C.G. Semper, Reisen im Archipel der Philippinen, Wissenschaftliche Resultate. Band 2, Suppl. 1, 1-78, Pls.A-F.
• Pease, W.H. (1860). Descriptions of new species of mollusca from the Sandwich Islands. Proceedings of the Zoological Society of London, 28: 18-37.
• Pease, W.H. (1871) Descriptions of new species of Nudibranchiate Mollusca inhabiting Polynesia. No.2. American Journal of Conchology. 7 (1): 11-19
• Risbec, J. (1928) Contribution a l'étude des nudibranches Néo-Calédoniens. Faune des Colonies Francaises 2(1): 328, pls.1-12.
• Rudman, W.B. (1984) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: a review of the genera. Zoological Journal of the Linnean Society 81: 115-273.
• Rudman, W. B. (1986) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Noumea purpurea and Chromodoris decora colour groups. Zoological Journal of the Linnean Society 86(4): 309-353.Baba, K. (1938) Opisthobranchia of Kii, Middle Japan. <i>Journal of the Department of Agriculture. Kyusyu Imperial University, 6(1)</i>: 1-19.

Bill Rudman

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