Chromodoris quadricolor (RuÈppell and Leuckart, 1830)

Yonow, Nathalie, Anderson, R. Charles & Buttress, Susan G., 2002, Opisthobranch molluscs from the Chagos Archipelago, Central Indian Ocean, Journal of Natural History 36 (7), pp. 831-882 : 852-853

Chromodoris quadricolor (RuÈppell and Leuckart, 1830)

(®gures 11e, f, 12A, B)

Doris quadricolor RuÈppell and Leuckart, 1830: 31 , pl. 9.

Chromodoris quadricolor: Rudman, 1977: 370 , pl. 1B rt, ®gure 19; Rudman, 1982b: 213; Yonow, 1989: 296, pl. 8.

Material. Chag96/16: 37 mm; inner reef between Ile du Sel and Ile Jacobin, Salomon Atoll; 12 February 1996; at 10 m depth. Chag96/42: 22 mm; inner reef of Ile Diamant, Peros Banhos Atoll; 19 February 1996; at 5 m depth. Chag96/51: 32 mm; inner reef of Grand Ile Mapou, Peros Banhos Atoll; 21 February 1996; at 4 m depth. Chag96/52a, b, c: live lengths not recorded; inner reef of Grand Ile Mapou, Peros Banhos Atoll; 21 February 1996; at 10 m depth; only three of nine individuals on patch of Halimeda algae collected. Chag96/87: 40 mm; inner reef of Nelson Island, Great Chagos Bank; 3 March 1996; at 26 m depth (radular preparation).

Description. Mantle wide, but not undulated, with a broad orange margin, the very edge of which was pale, and a thin submarginal white band (®gure 11e, f). Dorsal surface blue and black striped: one black band enclosed the area and one black median stripe ran back from rhinophores to anterior margin of gill pocket; in some specimens a pair of black stripes (continuous or incomplete) extended from behind the rhinophores to the sides of the gill pocket; in a few specimens additional black streaks were also present; the number of black stripes thus varied from three to ®ve, with additional streaks. Rhinophores orange; gills orange with limited ®ne white speckling on edges of plumes. Foot with orange ventral margin and blue and black stripes laterally.

The seven preserved specimens are very similar indeed, all retaining all the colours on the body and foot, with deeper orange gills and rhinophores. The radular formula of specimen 96/87 (40 mm alive) is 82 (1 3±4)3 62.0.62. The teeth are all denticulate on their outer sides (®gure 12A, B).

Geographic distribution. Western Indian Ocean: Chromodoris quadricolor has been recorded only from the Red Sea (Yonow, 1989) and Tanzania (Rudman, 1977, 1982b), so this record represents a signi®cant range extension.

Remarks. The variations in these specimens are within the range of variations seen in the Red Sea specimens, where the species is extremely abundant. In addition