Cladodactyla sicinski

O’Loughlin, P. Mark, Mackenzie, Melanie, Paulay, Gustav & VandenSpiegel, Didier, 2014, Four new species and a new genus of Antarctic sea cucumbers with taxonomic reviews of Cladodactyla, Pseudocnus, Paracucumidae and Parathyonidium (Echinodermata: Holothuroidea: Dendrochirotida), Memoirs of Museum Victoria 72, pp. 31-61 : 40

Cladodactyla sicinski (O’Loughlin, in O’Loughlin et al., 2013)

Dendrelasia sicinski O’Loughlin (in O’Loughlin et al.), 2013: 70–73, figs 1–3.

Figures 2 , 5 , 6 , 7 , 8 ; table 1

Material examined. Holotype of Dendrelasia sicinski . Western Antarctica, South Shetland Islands , King George Is, Admiralty Bay, 200–250 m, P. Presler and J. Siciński, 1 Mar 1980, NMV F189855 .

Other material.Western Antarctica, Elephant I. , 61.26°S 54.90°W, 158 m, RV Polarstern ANT–XXVIII/4 stn 191, 18 Mar 2012, NMV F193767 (1) ; 61.20°S 54.90°W, 63 m, Polarstern ANT–XXVIII/4 stn 190, 18 Mar 2012, NMV F193770 (1) ; 61.34°S 55.49°W, 155 m, stn 195, 19 Mar 2012, NMV F193768 (1) ; 60.88°S 55.45°W, 243 m, stn 208, 21 Mar 2012, NMV F193769 (1) ; 60.98°S 55.69°W, 92 m, stn 229, 24 Mar 2012, NMV F193771 (5) ; 61.14°S 55.69°W, 78 m, stn 230, 24 Mar 2012, NMV F193766 (1) ( UF tissue sequence code MOL AF 1298 ) ; South Shetland Is, 62.33°S 60.49°W, 119 m, stn 253, 29 Mar 2012, NMV F193772 (3) ( UF tissue sequence code MOL AF 1300 ) .

Description (emended). Body fusiform, cylindrical in mid-body, tapers roundly at both ends; preserved body up to 70 mm long, 28 mm diameter; body wall thin to thick, soft, leathery; 10 equal dendritic tentacles; calcareous ring evident and calcified in small specimens, but becoming decalcified in 15 mm long specimen, and thus no longer evident in larger specimens; dorso-lateral radial body wall thick, soft; tube feet on dorso-lateral radii in paired close zig-zag rows on each radius, series extended across dorsal inter-radius anteriorly and posteriorly to border an external brood-protecting marsupium, dorso-lateral radial tube feet smaller and more numerous than ventral tube feet, tube feet on dorso-lateral radii may be withdrawn into pits; tube feet on trivium larger and fewer than on bivium, ventral radial series in paired zig-zag rows, fewer in outer rows of ventro-lateral series; shallow median groove in flat longitudinal muscles; single polian vesicle; paired, unbranched tufts of hermaphroditic gonad tubules, gonoduct opens at pore in mid-anterior marsupium; lacking male genital papilla; respiratory trees arise from 3–4 basal sources, each with dendritic branches, extending about half length of coelom.

Larger specimens lack mid-dorsal and mid-ventral body wall ossicles; 15 mm long specimen with prominently spinous rod, X-shape, Y-shape and branched forms up to 136 µm long. Tentacle ossicles predominantly perforated plates, some rods; plates thin, irregular, with denticulate margins, sometimes with fine surface spines, and larger central perforations; rods frequently with distal and lateral perforate developments and denticulate margin; plates and rods both up to 200 µm long. Introvert lacking ossicles. Dorsal tube feet endplates up to 480 µm diameter; tube foot support plates oval to sub-rectangular to pear-shaped to half-moon shaped, 2 large perforations centrally, margin denticulate to spinous to smooth, some with fine surface spines, up to 160 µm long. Ventral tube foot endplates up to 960 µm diameter, outer rim of endplate comprises fused irregular branched rods, not perforations, central perforations slightly larger than outer ones, tube foot support plates oval with surface and marginal spinelets, surface sometimes smooth, 4 large central perforations, 2 largest perforations adjacent, 2 smaller distal perforations, up to 208 µm long. Peri-anal body wall with plates, crosses, rods; single-layered perforated anal plates up to 320 µm wide, plates irregularly oval with marginal spines or denticulations, with or lacking surface spines, frequently 4 large central perforations in cross formation as described above; amongst the body wall ossicles small clusters of irregular distally spinous crosses of variable rod thickness, arms frequently bifid, sometimes with branches joined to create 8 perforations and slightly concave sub-rectangular plates, crosses up to 112 µm long; rare spinous or denticulate rods, with or without distal perforations, up to 96 µm long; all three peri-anal ossicle forms inter-grade.

Colour. Live: body and tentacles pale yellow, oral disc red. Preserved: body variably off-white to pale grey-brown; tentacle discs with paired brown markings anterior to each tentacle, sometimes fine brown spotting on the oral disc.

Distribution. Western Antarctica, South Shetland Is, Elephant I., 63– 250 m.

Remarks. The SEM images of peri-anal ossicles in the recent Susanne Lockhart collection of larger specimens of a species of Cladodactyla fromtheSouthShetlandIslandsaredistinctive. They are identical in general shape and form with the peri-anal ossicles from a smaller specimen from Admiralty Bay in the South Shetland Islands illustrated in O’Loughlin et al. 2013 for the new genus and species Dendrelasia sicinski O’Loughlin, 2013 . The small specimen from Admiralty Bay is morphologically conspecific with the larger specimens of the recent Lockhart collection. Dendrelasia is a junior synonym of Cladodactyla .

In specimens of Cladodactyla sicinski there is a distinct dorsal external marsupium. Indentations present in the soft inter-radial dorsal body wall within the marsupium suggest a prior presence of embryos or juveniles. Cladodactyla sicinski is distinguished from the other Cladodactyla species by the combination of: presence of a dorsal external marsupium; dorso-lateral radial tube feet series continuous anteriorly and posteriorly across the dorsal inter-radius to create a complete border to the marsupium; 10 equal tentacles; tentacle ossicles predominantly plates; absence of ossicles in the introvert; presence of tube feet support plate ossicles; presence of spinous crosses in the peri-anal body wall.

Figures

Figure 2. Maximum likelihood tree for Cladodactyla–Heterocucumis–Staurocucumis clade, based on COI sequences, T92+G+I model, 100 bootstrap replicates, Laevocnus laevigatus as outgroup. Filled circles>0.95 bootstrap support; hollow circles>0.70 bootstrap support.

Figure 5. Cladodactyla sicinski (O’Loughlin, 2013) (preserved specimen, NMV F193767). a, right lateral view; b, tentacles; c, dorsal view (marsupium surface); d, ventral view; e, photos of two live specimens (South Shetland Islands; NMV F193772; photos by Susanne Lockhart).

Figure 6. Photo of a live specimen of Cladodactyla sicinski (O’Loughlin, 2013) in situ in Fildes Bay on King George Island in the South Shetland Islands (photo taken by Dirk Schories (UACh) and used with permission).

Figure 7. SEM images of ossicles from specimen of Cladodactyla sicinski (O’Loughlin, 2013) (NMV F193767). a, tentacle ossicles; b, ventral tube foot ossicles with presumed to be residual body wall plate (top) and tube foot support plate (bottom); c, ventral tube foot endplate fragments with rim of fused outer marginal support rods.

Figure 8. SEM images of peri-anal spinous cross and spinous plate ossicles from specimen of Cladodactyla sicinski (O’Loughlin, 2013) (NMV F193771).