Chromodoris alius
Rudman, 1987

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

DISTRIBUTION

Western Indian Ocean

PHOTO

Holotype. Ocean Rd. Beach, entrance to harbour, Dar es Salaam, Tanzania, September 1973. 40mm long alive. Photo: Bill Rudman.

Note added 7 March 2005: see message #13260 suggesting this species may be synonymous with C. aureopurpurea, C. albopustulosa, and C. rufomaculata, which would give it a wide Indo-West Pacific distribution.

The mantle is creamy-white with six irregular grayish translucent patches arranged as in C. rufomaculata but interconnected with other elongate translucent patches around the inner part of the mantle skirt. All over the mantle are small translucent pits each with a golden-yellow spot giving the mantle an uneven pitted appearance. At the mantle edge is a band of purple elongate marks and inside this a diffuse submarginal band of milky yellow.

The rhinophore stalks are translucent white and the clubs are dark brown or black with white edgings. The gills are translucent with white edging. The underside is all white except for the mantle edge where the purple shows through from the dorsum. The wide mantle skirt is thrown into a number of folds down each side. The gills are simple.

Chromodoris alius is very similar in colour to both C. rufomaculata and C. aureopurpurea. It differs from C. rufomaculata in that the golden yellow spots are each at the base of a translucent pit in C. alius, whereas in C. rufomaculata they are, if anything, slightly raised and usually on the white background pigmentation.

It differs from C. aureopurpurea in that it has a continuous yellow band inside the row of purple spots at the mantle margin, while in C. aureopurpurea each purple spot has a yellow cap around its inside edge. Also, in C. aureopurpurea the purple spots on the mantle are larger. The radula of C. alius is more like that of C. aureopurpurea than that of C. rufomaculata, but differs from the former in details of the denticulation.

The species has been recorded from Sth Africa, Tanzania and Reunion Is. suggesting that this species is an Indian Ocean endemic. The similarities in colour pattern and radular morphology to C. aureopurpurea suggest that they are a pair of closely related species, C. aureopurpurea being endemic to the western Pacific and C. alius to the western Indian Ocean.

Reference:
• Rudman, W.B. (1987) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris epicuria, C. aureopurpurea, C. annulata, C. coi and Risbecia tryoni colour groups. Zoological Journal of the Linnean Society, 90: 305-407.

Authorship details
Rudman, W.B., 2000 (June 22) Chromodoris alius Rudman, 1987. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/chroaliu

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