Prototrochus taniae 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 taniae O’Loughlin sp. nov.

Figures 10a–d, 11; Tables 1, 2

Material. Holotype: Eastern Australia, New South Wales, 54 km ESE of Nowra, 34°53’S, 151°17’E, 996– 990 m, upper continental slope, mud, fine sand, fine shell, stn SLOPE 53, RV Franklin, G.C.B. Poore et al., 22 Oct 1988, NMV F59191 (with microscope slide of ossicles).

Paratypes: Type locality and date, F59192 (4, with 2 microscope slides of ossicles and 1 anterior body mount).

Description. Up to 7 mm long; calcareous ring and body diameter 1.0 mm; 10 peltato-digitate tentacles, each with 3 pairs of digits; calcareous ring symmetrical, dorsal and ventral plates subequal, 10 plates, radial and interradial plates with single long anterior spire, radially digitiform and distally rounded, interradially narrower and distally pointed, all plates with posterior indentations, lacking posterior projections; single dorsal madreporite; single ventral polian vesicle; branched gonad tubules.

Body wall ossicles massed wheels only, present dorsally and laterally, absent ventrally: average (37) wheel diameter 232 μ m (range 192–248 μ m); spokes thin, average 9 per wheel (7–10); wheel rim slightly angular rounded, not scalloped, rounded angles between spokes, flat across spokes; wheel hubs simple, lacking perforations, hub diameter 48 μ m for wheel diameter 248 μ m (20%), hub diameter 40 μ m for wheel diameter 208 μ m (19%); teeth distributed regularly around inner rim, all pointing towards hub, bluntly rounded, 2 sizes, longer teeth aligned with spokes, shorter teeth between spokes; for wheel diameter 240 μ m longer teeth 40 μ m, shorter teeth 32 μ m; when 9 spokes 27 teeth (33%), when 8 spokes 24 teeth (33%). Tentacles lacking ossicles.

Colour. Off-white, translucent; tentacles each with brown lateral bands.

Distribution. Eastern Australia, off southern NSW, upper continental slope; 996 m.

Etymology. Named for Tania Bardsley (formerly of the Marine Science Section of Museum Victoria), in appreciation of her personal collaboration in my holothuroid research, and her significant contribuiton to marine science systematics.

Remarks. Prototrochus taniae O’Loughlin sp. nov. is based on 1 complete and 5 small part-specimens. 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 angular rounded wheel rims, and 2 sizes of teeth, the longer teeth aligned with spokes, distinguish P. taniae sp. nov. from P. australis (Beljaev and Mironov) , P. burni sp. nov. and P. staplesi sp. nov ( Table 1). In the SEM images of the larger wheels in P. taniae Didier observed rare ones with rounded rims and subequal teeth, but the wheels were predominantly as described and illustrated with longer teeth over the spokes. Beljaev and Mironov (1981) reported no such character. Rare small wheels were observed in the SEM images of the paratype of P. taniae , some with a rim like P. staplesi sp. nov. and with more numerous spokes. The diagnosis here is based on large wheel comparisons. The lengths of the wheel teeth in the description above were measured to the edge of the rim (for wheel diameter 240 μ m longer teeth 40 μ m, shorter teeth 32 μ m). The SEM measurements (average 21.0 μ m) were measured to the inner rim (see fig. 10d).