Tambja amakusana Baba, 1967

Yonow, Nathalie, 2012, Opisthobranchs from the western Indian Ocean, with descriptions of two new species and ten new records (Mollusca, Gastropoda), ZooKeys 197, pp. 1-130 : 19

Tambja amakusana Baba, 1967 Plate 23

Tambja amakusana Baba, 1967: 15, fig. 3 (Japan); Marshall and Willan 1999: 56, fig. 87 (Great Barrier Reef); Pola et al. 2006: 510, figs. 10F, 13D, 15A-F (Japan, Papua New Guinea).

Material.

Maldives: 11 mm (6 × 2 mm pres.), Old Shark Point, Thilafalhu reef, south end of North Malé Atoll, 10 m depth, 14 August 1995, leg. RC Anderson & SG Buttress.

Description.

Animal dark to medium green with some relatively large white spots. Tail extremely long, almost half body length, and body appears to have been smooth. Five small multi-pinnate gills beige with purple tips; rhinophores beige suffused with purple; margins of rhinophore sheaths pale yellow. Flattened oral tentacles visible when crawling.

The preserved specimen is well relaxed: body light blue-green, gills and rhinophores white, rhinophores with 12 lamellae. Marshall and Willan (1990) state that there is no rhinophoral sheath; none is visible on the specimen but the rim of the right rhinophore is visible in Plate 23 where it catches the light. Baba (1967) described and illustrated the genital opening just below the right rhinophore whereas Pola et al. (2006) located it halfway between the gills and the rhinophore; in this specimen, an orange puckered pore also occurs halfway. The collectors noted that the animal laid a light pink spiral egg mass 4 mm in diameter its second night in captivity; it has barely more than three complete whorls laid close together (Plate 23).

Distribution.

Tambja amakusana is recorded for the first time from the Indian Ocean; all literature records to date are listed in the synonymy. The only similarly small species with purple tips to the gills and rhinophores is Tambja limaciformis (Eliot), but this species is usually brick to orange red, with many more white spots, occurring throughout the tropical Indo-West Pacific (e.g. Yonow 2008).