Phyllidiopsis shireenae Brunckhorst, 1990

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 : 59-60

Phyllidiopsis shireenae Brunckhorst, 1990 Fig. 27, Plate 76

Phyllidiopsis shireenae Brunckhorst, 1990: 557, figs. 1-4 (N Queensland, Papua New Guinea, Solomon Islands); Domínguezet al. 2007: 97, fig. 7 (Papua New Guinea); Yonow 2011: 942 (Indonesia).

Material.

Maldives: three specimens 60 × 24 mm (NY-100), 75 × 25 mm (NY-98), and 95 × 33 × 20 mm (NY-99), Maaya Tila, Ari Atoll, 8-30 m depth, 17 May 1990, leg. N Yonow, photos H Voigtmann; 80 mm length (NY dive 42), Maaya Tila, Ari Atoll, 33 m depth, 18 January 1991, leg. N Yonow; individual 40 mm length (photographed but not preserved), Vihafushi Tila, Baa Atoll, 18 m depth, 7 March 1991, S Harwood; individual 30 mm length (photographed but not preserved), Vadhoo Reef, South Malé Atoll, 16 m depth, 3 April 1991, S Harwood; photographs of several individuals, Ari Atoll, approx. 20 m depth, late 1980s, H Voigtmann.

Description.

Body elongate oval, flexible and rubbery, with high profile. Ground colour semi-translucent pink with black line surrounding central region; four smaller perpendicular lines extending to margin in opposing pairs. Central region bears high median crest and lower lateral one either side. Crests composed of irregular granular compound tubercles, opaque in comparison with body. Rhinophores and anal papilla located within black oval. Rhinophores translucent pink, 12 to 19 oblique lamellae; anus conical, located on last tubercle of central crest, visible on larger specimen Plate 76; both extend through raised rims. Outside the black ellipse, a row of large tubercles is followed by a row of smaller ones, also compound and opaque pink-white in life. Metapodium projected beyond the mantle in life. Black band in crevice where hyponotum meets foot behind gills; this black line extends posteriorly along top of metapodium in one specimen. Gills black, genital opening a white swelling on right side. Propodium nearly divided in smaller specimens and notched in the largest. White head and fused oral tentacles, very short with groove on outer sides (figs. 27A).

Internally, three specimens from the Maldives proved to be identical (the fourth was badly preserved). One specimen (95 mm) everted its mouthparts completely during preservation (Fig. 27B, D). The mouth leads to a short oral tube which, in one specimen, is narrow and contracted like a concertina (Fig. 27C). Where it thickens into the pharyngeal bulb, there is a band of pigment, incomplete dorsally. The pharyngeal bulb is extensible, as evidenced by the specimen illustrated in Fig. 27D. A sharp demarcation exists where the pharynx joins the bulb; the bulb turns anteriorly and loops posteriorly, passing through the nerve ring. The posteriorly-directed portion is of equal length to the anteriorly-directed segment, and inserts into the oesophagus at a constriction. The oesophagus is a thicker banded tube leading into a sac-like structure with which it is continuous (the muscular oesophageal segment), and opens into the digestive gland. The pathway from the oesophagus to the digestive gland follows a Z-shaped route, located in the anterior quarter of the digestive gland. Almost in a continuous line with the oesophagus, a long muscle attaches and runs under the intestine and pericardium to emerge on the other side. The intestine then runs along the midline to the anus.

Distribution.

These records greatly extend the range of the species from the tropical western Pacific to the central Indian Ocean. It was previously described from eastern Australia, the Solomon Islands ( Brunckhorst 1990), Papua New Guinea ( Domínguez et al. 2007), and Ambon, Indonesia ( Yonow 2011). The internal anatomy of the I ndian Ocean specimens differs somewhat from Brunckhorst’s material, which is presented as a generalised figure, but it is unlikely that more than one species are involved: the detailed description and illustrations of the Papua New Guinea material are more comparable ( Domínguezet al. 2007).