Myriotrochus antarcticus Smirnov and Bardsley, 1997

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 : 68

Myriotrochus antarcticus Smirnov and Bardsley, 1997

Figures 3 , 4 ; table 2

Myriotrochus sp. MoV 2039 O’Loughlin et al., 1994: 553, table 2. Myriotrochus antarcticus Smirnov and Bardsley, 1997: 109–111 , fig. 1, table 1.— O’Loughlin et al. 2009: 9.

Material examined. Holotype. Eastern Antarctica, 66º55'S 62º32'E, 113 m, M. O’Loughlin, 11 Feb 1993, NMV F69125 .

Other material. Western Antarctica, South Orkney Is, 60.82ºS 46.49ºW, 216 m, BAS stn PB–EBS–4, 18 Mar 2006, NMV F168638 (1) ; F168643 (1 whole, for molecular sequence, tissue code MOL AF 805 ); RBINS IG 31 459 (2 whole, for SEM figures); NHM 2010 . 48–49 (2); Weddell Sea , 71.25º S 13.00º W, 193 m, RBINS 628686 (1).

Diagnosis (following Smirnov and Bardsley 1997 for Prydz Bay holotype). Myriotrochid species up to 8 mm long; 12 peltato-digitate tentacles, up to 8–12 digits per tentacle, distalmost pair longest; lacking tentacle ossicles; calcareous ring comprising 10 plates, ventral plates not significantly longer than dorsal plates; two dorsolateral radial plates each with 2 prominent tapering anterior projections, remaining plates with single prominent tapering anterior projection; posterior margin of calcareous ring slightly undulating, not concave; ossicles myriotrochid wheels only, scattered sparsely and uniformly throughout body wall; wheels of one type, all teeth pointing to centre of hub; wheel ossicle diameters 140–150 µ m (for S Orkneys specimens 80–144 µ m; for Weddell Sea specimen 108–133 µ m), spokes 15–16 (for S Orkneys 13–16; for Weddell Sea 13–15), teeth 22–24 (for S Orkneys 19–25; for Weddell Sea 22–24), spokes/teeth % 66.7–68.2 (for South Orkneys 64–68; for Weddell Sea 60.8–65.2), hub diameter/wheel diameter % 18.0–18.6 (for S Orkneys 16.0–18.1), teeth length/wheel diameter % 18.0–18.6 (for S Orkneys 14.4–16.0).

Colour (preserved). Body grey, translucent; tentacles white.

Distribution. Antarctic shelf species; Eastern Antarctica, western MacRobertson Shelf, 113 m; Western Antarctica, South Orkney Is, 216 m; Weddell Sea, 193 m (range 113–216 m).

Remarks. For Myriotrochus antarcticus Smirnov and Bardsley, 1997 there are only minor morphological differences for the limited number of measurements for specimens from the Scotia Sea, Weddell Sea and Prydz Bay, suggesting a morpho-species with an eastern and western Antarctic distribution.

Figures

Figure 3. Photo of Myriotrochus antarcticus Smirnov and Bardsley, 1997, showing 12 peltato-digitate tentacles, calcareous ring with high anterior pointed projections, and wheels distributed throughout body wall (7 mm long; S Orkney Is, 216 m; RBINS IG 31 459).

Figure 4. Myriotrochus antarcticus Smirnov and Bardsley, 1997 (S Orkney Is, 216 m; RBINS IG 31 459). a, SEM of plates of the calcareous ring with prominent anterior projections and undulating posterior margin and canals, dorso-lateral radial plate (lower left) with two anterior projections; b, SEM of wheels from the body wall.