Prototrochus barnesi, O’Loughlin & VandenSpiegel, 2010

O’Loughlin, P. Mark & VandenSpiegel, Didier, 2010, A revision of Antarctic and some Indo-Pacific apodid sea cucumbers (Echinodermata: Holothuroidea: Apodida), Memoirs of Museum Victoria 67, pp. 61-95 : 71-73

Prototrochus barnesi sp. nov.

Figure 6 ; table 2

Material examined. Holotype. Antarctica, Scotia Sea , Shag Rocks, 53.63°S 40.91°W, 206 m, BAS stn SR–EBS–4, 11 Apr 2006, NMV F168637 .

Paratypes. Type locality and date, NHM 2010.54 (1) ; RBINS IG 31 459 (1, SEM).

Diagnosis. Myriotrochid species up to 3 mm long; 10 peltato-digitate tentacles, 7 digits per tentacle, including a distal terminal one; tentacle rods present, straight and curved, some with central swelling, some with swollen end, 40–170 µ m long; sparse myriotrochid wheels in body wall, slightly scalloped margin at each tooth; wheel ossicle diameters 72–104 µ m, spokes 13–15, teeth 22–27, spokes/teeth % 50–59, hub diameters 19–26 µ m, hub diameter/wheel diameter % 25–38, teeth length/wheel diameter % 12–20.

Colour (preserved). Off-white.

Distribution. Western Antarctica, Scotia Sea, Shag Rocks, 206 m. Etymology. Named for David Barnes (British Antarctic Survey), in appreciation of his role in the BAS BIOPEARL expeditions and the collection of specimens studied here.

Remarks. Belyaev and Mironov (1982) referred 12 species to their new genus Prototrochus . O’Loughlin and VandenSpiegel (2007) added three new Prototrochus species from the continental slope of Australia, all lacking tentacle ossicles. The only Prototrochus species recorded from Antarctica is Prototrochus bipartitodentatus ( Belyaev and Mironov, 1978) from the South Sandwich Trench at 7700–8100 m. This species lacks tentacle rods and has external teeth around the rim of the wheels. Prototrochus barnesi sp. nov. has wheels with internal teeth only, and has tentacle rods, a rare character for Prototrochus species. The only other Prototrochus species with tentacle rods is the similarly small Prototrochus minutus ( Östergren, 1905) , described from the coast of Korea at 60–65 m depth. Three diagnostic characters distinguish Prototrochus minutus from Prototrochus barnesi : sometimes distally and centrally branched tentacle rods; longer tentacle rods (mostly 140–200 µ m long); significantly larger wheels (mostly 100– 150 µ m diameter).

Figures

Figure 6. Prototrochus barnesi sp. nov. (Shag Rocks; RBINS IG 31 459). a, SEM of plates of the calcareous ring with prominent single anterior projections; b, SEM of wheels from the body wall; c, SEM of rods from tentacles.