Halgerda tesselata ( Bergh, 1880 )

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 : 844

Halgerda tesselata ( Bergh, 1880)

(®gure 11a)

Halgerda tesselata Bergh : Rudman, 1978: 65, ®gures 4c, d, 6; Carlson and HoOE, 1993: 16, ®gures 1±3.

Material. Chag96/30a, b: 15 mm, 25 mm; outer reef, Ile de la Passe, Salomon Atoll; 14 February 1996; at 8 m depth.

Description. The body was orange-yellow, with a reticulate pattern of raised ridges on the dorsal surface forming incomplete triangular shapes (®gure 11a). The areas between the ridges were dark brown with many small white spots. The foot was orange-yellow with a very dark brown, almost black, line on the metapodium. The long rhinophores had elongated tips; the clubs were dark brown, and the stalks were translucent cream with a thick dark brown line posteriorly. The orange rhinophore sheaths were short, and the gills were white, each with the rachis coloured dark brown externally.

Geographic distribution. Indo-West Paci®c: East Africa ( Eliot, 1905) to Australia (Rudman, 1978), Micronesia ( Bergh, 1880) and Guam (Carlson and HoOE, 1993).

Remarks. Halgerda tesselata has brown marks in the junction between the foot and mantle and a median line on the top of the metapodium. These are absent in the preserved material from Chagos but present in two specimens from Kenya (Yonow, unpublished, 10 and 25 mm preserved lengths); two specimens from the Maldives (11 and 15 mm preserved lengths, coll. R. C. Anderson and S. G. Buttress, 1996) are completely faded except for a little dark speckling in the dorsal depressions.