Phyllidia coelestis Bergh, 1905

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 : 45-46

Phyllidia coelestis Bergh, 1905 Plate 62

Phyllidia coelestis . - Yonow et al. 2002: 862, fig. 16b (Chagos) and references therein; Apte 2009: 171, fig. 2r (Laccadive Islands).

Phyllidia elegans . - Edmunds 1972: 82, fig. 4b (Seychelles) (non Phyllidia elegans Bergh).

Phyllidia varicosa . - Gosliner 1987: 90, fig. 152 (South Africa) (non Phyllidia varicosa Lamarck).

Phyllidia alia Yonow, 1984: 224 figs. 6C, D, 7A, 8F, G (Sri Lanka).

Material.

Madagascar: 65 × 25 mm (PK-C), Ampangorina, Nosy Komba, 1 m depth on Acropora , 30 January 1992, leg. P Kemp. - Tanzania: photographs of two individuals, Mafia Island, shallow water, 15 January 2005 and 04 July 2005, A de Villiers. - Seychelles: 32 × 12 mm (PK-FF), Lilôt, NW Mahé, 15 m on encrusted coral, 26 April 1992, leg. P Kemp; 32 × 15 mm preserved (NHMUK acc. no. 2222), slightly curled, east side of East Channel, Aldabra, 1 m depth in coral, 25 September 1967, leg. JD Taylor; 49 × 15 mm preserved (NHMUK acc. no. 2222), Passe Femme, Aldabra, in shallow water beneath coral, 29 November 1967, leg. JD Taylor. - Maldives: 23 × 11 mm preserved (NHMUK ref. M/02/B/42), Gan, 04 September 1964, PSD Maldive Islands Expedition. - La Réunion and Mayotte: numerous individuals photographed, 20-45 mm in length http://seaslugs.free.fr/nudibranche/a_intro.htm.

Description.

Ground colour granular blue-white with three black lines: median line containing orange-tipped tubercles, two smooth lateral lines. Lateral lines normally meet anteriorly, and extend to margin usually as U-shape, but remain separated posteriorly. Outside the black lines, mantle bears tubercles, black flecks, and smaller scattered pustules toward edge; larger tubercles may have orange tips. Rhinophores bright orange, up to 16 lamellae; row of orange tubercles originates behind each rhinophore. Ventrally, propodium notched or deeply concave; all specimens have long tapering oral tentacles, grooved laterally and bearing black pigment on dorsal surfaces extending ventrally onto bases.

Distribution/Remarks.

These specimens and photographed individuals belong to the typical form of Phyllidia coelestis , a commonly recorded species in the western Indian Ocean and occurring as far south as South Africa. Another group of specimens also identified as Phyllidia coelestis ( Brunckhorst 1989, 1993; Yonow 2011 as dark form) has a central oval region where the ground colour is black and only a marginal band around it is blue-white. The edge of the central black area is irregular and may form short rays extending a little way into the blue-white margin, identical to that of Phyllidia (Fryeria) picta (p. 56), but this form has not been found in the western Indian Ocean.