Prototrochus staplesi O’Loughlin, 2007

O’Loughlin, P. Mark, 2007, New apodid species from southern Australia (Echinodermata: Holothuroidea: Apodida), Memoirs of Museum Victoria 64, pp. 53-70 : 68

Prototrochus staplesi O’Loughlin sp. nov.

Figure 10f; Table 1

Material. Holotype. Eastern Australia, Victoria, 67 km S of Point Hicks, 38°24’S, 149°16’E, 1119 m, upper continental slope, fine mud, stn SLOPE 67, RV Franklin, G.C.B. Poore et al., 25 Oct 1988, NMV F94698 (microscope slide of wheel ossicles).

Description. Anterior body part; length 1.2 mm; calcareous ring diameter 1.0 mm; 10 peltato-digitate tentacles; calcareous ring symmetrical, 10 plates, dorsal and ventral plates subequal, radial and interradial plates with single long anterior spire, radially digitiform and distally narrowly rounded, interradially narrower and distally pointed, all plates with posterior indentations, lacking posterior projections.

Body wall ossicles massed wheels only: average (10) wheel diameter 136 μ m (range 112–152 μ m); spokes thin, average 8 per wheel (range 7–9); wheel rim slightly scalloped to straight across each tooth; wheel hubs simple, not perforated; hub diameter 24 μ m for wheel diameter 152 μ m (16%), hub diameter 16 μ m for wheel diameter 112 μ m (14%); wheel teeth subequal in size, distributed regularly around inner rim, not aligned with spokes, bluntly rounded, all pointing towards hub; teeth large, small 9 spoke wheel with 18 teeth (50%), large 8 spoke wheel with 20 teeth (40%); tooth length 16 μ m for wheel diameter 112 μ m (14%), tooth length 24 μ m for wheel diameter 152 μ m (16%). Tentacles lack ossicles.

Colour. Off-white, translucent; tentacles lacking brown spots.

Distribution. Eastern Australia, off eastern Victoria, upper continental slope; 1119 m.

Etymology. Named for David Staples (Marine Research Group of Victoria; Honorary Associate of Museum Victoria), in appreciation of his decades of generous and dedicated contribution to marine research and Museum Victoria, and his invaluable service to the Marine Research Group.

Remarks. Prototrochus staplesi O’Loughlin sp. nov. is based on a single small part-specimen. Tentacles, calcareous ring, and wheel ossicles are all present, and adequate for a specific diagnosis. The symmetrical calcareous ring, with single long anterior projection on each plate and 10 tentacles, wheels with evenly distributed teeth pointing towards the hub, and absence of rod ossicles, identify the new species as a Prototrochus Beljaev and Mironov, 1982 . The small diameter of the wheels, wheel rims slightly scalloped or straight across each tooth, small wheel hubs, and large teeth distinguish P. staplesi sp. nov. from P. australis (Beljaev and Mironov) , P. burni sp. nov. and P. taniae sp. nov. (below) ( Table 1).