Chromodoris tritos
Yonow, 1994

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

DISTRIBUTION

Maldive Islands.

PHOTO

UPPER: C. tritos, Ellaidhoo Island, Maldives. size 4 cm, PHOTO: Erwin Koehler.
LOWER: For comparison here are photos of: A, C. geminus, Tanzania; PHOTO: Bill Rudman. B, C. kuniei, Great Barrier Reef, Queensland, PHOTO: G. Avern.

This animal has been recorded a number of times from the Maldives, off the southwest coast of India. In external shape and colour it is very similar to Chromodoris geminus, found only in the Indian Ocean, and Chromodoris kuniei, found only in the western Pacific. As I have reported earlier (Rudman, 1987) their ranges overlap in the Indonesian Archipelago, both species being found at Christmas Island.

The Maldives animal could be a pale colour form of either species. However Yonow, considers it to be a distinct species which she has named C. tritos. The only point of difference she notes concerns the morphology of the radular teeth. In the other two species, the outermost teeth are shorter and have a rounded tip. In C. tritos she states that scanning electron microscope photos show that the outer lateral teeth retain the hook shape of the inner teeth, rather than shortening and rounding off as in the other two species. However her photos suggest that the edge of the radular ribbon has curled under during the preparation of the SEM mount and rather than viewing the outermost teeth we are looking at some of the 'normal' inner teeth. At this stage I am not sure that C. tritos is a good species. I suspect it is a pale form of C. geminus.

Yonow (1994), refers to a letter of mine in which she says I record C. tritos from the Seychelles and from Christmas Island (Indian Ocean). I did not expect my correspondence to be interpreted this way, as neither of the finds I referred to in my letter applied to Yonow's colour form or species. The Seychelles record is an unidentifiable juvenile, and as I have reported earlier (Rudman, 1987) typical forms of both C. geminus and C. gleniei occur at Christmas Island.

References:
•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. (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.
•Yonow, N. (1994) Opisthobranchs from the Maldive Islands, including descriptions of seven new species (Mollusca: Gastropoda). Revue fr. Aquariol., 20(4): 97-130.

Authorship details
Rudman, W.B., 1999 (October 16) Chromodoris tritos Yonow, 1994. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/chrotrit

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