Haminoea cymbalum (Quoy & Gaimard, 1833)

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 : 4

Haminoea cymbalum (Quoy & Gaimard, 1833) cf. http://species-id.net/wiki/Haminoea_cf_cymbalumPlate 1

Haminoea cymbalum . - Rudman 1971: 558, fig. 1 (Fiji, Hawaii); Marshall and Willan 1999: 25 fig. 23 (Great Barrier Reef); Gosliner et al. 2008: 26 (Mozambique, Madagascar + West Pacific); Apte 2009: 165, fig. 1c (Laccadive Islands).

Material.

Maldives: two specimens approx. 20 mm length (MDV/AB/96/23), Vilufushi lagoon, Thaa Atoll, 3 m depth, 31 March 1993, leg. RC Anderson & SG Buttress. - La Réunion: photographs of numerous individuals http://seaslugs.free.fr/nudibranche/a_intro.htm.

Description.

Globose shell thin, transparent, too small to accommodate body completely; shell 15 mm, living animal up to 25 mm. Body pale green with large and small orange spots, part contained within the shell much darker green than both head and tail. Larger orange spots and patches underlying shell outlined with white or very pale green.

Infrequently, huge mating congregations are observed, with numbers of up to 100 individuals per m2 in February 2007 in La Réunion, which lasted approximately one week (P Bidgrain, pers. comm. and http://seaslugs.free.fr/nudibranche/a_intro.htm). These aggregations were not observed again until 2010, but with a much smaller number of animals, only 100 individuals in total (P Bidgrain, pers. comm.).

Distribution/Remarks.

Haminoea cf. cymbalum has been rarely recorded in the Indian Ocean; it is more common in the western Pacific. Difficulties arise with the name of this well-known species: both Burn (in Marshall and Willan 1999) and Carlson and Hoff ( Sea Slug Forum 1999) suggested that the shell representing the type in the MNHN (Paris) is not the same species; therefore this species would take the next available name, which is Haminoea simillina (Pease). Additionally, there are several other species differing in colour, radula, and gizzard plates, so further work is needed; deposits of individual specimens such as these in museums with their descriptions and photographs will ensure that enough material is made available for future workers.