Phyllidia multituberculata Boettger, 1918

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 : 48-50

Phyllidia multituberculata Boettger, 1918 Fig. 20, Plate 66

Phyllidia multituberculata Boettger, 1918: 129, pl. 8 figs. 4 a–c (Aru Islands, Indonesia); Yonow 1996: 487, figs. 2 A–E, 3 A–G, 4B, tab. 1 (Seychelles and Mauritius).

Phyllidia ocellata . - Yogesh Kumar et al. 2011: 111, fig. 3b (India) (non Phyllidia ocellata Cuvier).

Material.

Typical form: Socotra: 30 × 16 mm pres. (St. 064, SAM1), Quatub Bay, 18 March 1999, leg. S Al-Moghrabi.

Black form: Maldives: single specimen 14 × 8 mm crawling (NY-167), Kudhiboli Tila, Felidhoo Atoll, 21 m depth, 15 January 1991, leg. N Yonow; two specimens together 28 × 20 mm and 30 × 21 mm both preserved, Maayafushi House Reef, Ari Atoll, 34 m depth, 18 December 1991, leg. H Voigtmann; 14 mm (MDV/AB/96/2), Cocoa House reef, South Malé Atoll, 16 m depth, 01 May 1996, leg. RC Anderson & SG Buttress; photos of one individual, 1986-1994, J Hinterkircher. - Sri Lanka: two pres. specimens 21 × 15 mm and 25 × 18 mm and photographs of a juvenile, Unawatuna, S of Galle, 26-28 December 2010, S Kahlbrock.

Description.

The Socotra specimen is of the typical form described and illustrated by Boettger, with five black patches on each side. This is the commonly occurring species in the Indian Ocean; see Yonow (1996) for descriptions, illustrations, and discussions. The white ring surrounding the black patch is visible in the preserved specimen and the oral tentacles are illustrated for comparison (Fig. 20A). The anterior margin of the foot is bilaminate, the head is visible, and the conical oral tentacles have a groove on their outer sides.

The Maldives and Sri Lankan specimens differ in colour pattern from the Socotra specimen but are identical to each other, completely black with numerous orange mushroom-shaped tubercles: some had a white ring at the base when alive (Plate 66), and still visible in the preserved specimens. Tubercles vaguely organized in longitudinal rows over dorsum, tubercles in central row largest. Rhino-tubercles present as well as single very large tubercle behind and between them. Margin orange, somewhat scalloped along inner margin bordering black, with single small tubercles aligned along edge. In Sri Lankan specimens, white submarginal line. Rhinophores deeper shade of orange than tubercles and margin, raised pocket rims also orange. Ventrally, foot of black and orange specimens deeply divided (convoluted for its entire margin in the largest specimen), head bipartite, separated oral tentacles digitiform (Fig. 20B), most similar to those of Phyllidia multituberculata form undula (fig. 5B in Yonow 1996). In smaller, more relaxed, Maldive specimen (NY-167), thickened anterior margin of foot concave, head barely visible, oral tentacles conical.

Remarks.

Dissection of the 28 mm Maldive animal shows that the digestive anatomy is typical for the genus (Fig. 20C). Significantly, it has a segmented asymmetrical pharyngeal bulb as described and illustrated for Phyllidia multituberculata and Phyllidia multituberculata form undula. This feature, in addition to the colour patterns, separates the Indian Ocean Phyllidia multituberculata from the Pacific Phyllidia ocellata Cuvier, which has a symmetrical pharyngeal bulb (e.g. Yonow 1996, Domínquez et al. 2007, Yonow 2011). Molecular studies are revealing cryptic species with more limited distributions for what were previously thought to be widely distributed variable species (e.g. for Bulla see Malaquias and Reid 2008, for Melanochlamys see Krug et al. 2008, and for Thuridilla see Carmona et al. 2011), and it is probable that molecular studies will reveal many more phyllidiid species than are currently accepted. It is therefore preferable to describe geographical and colour forms separately and clearly.