Molpadiodemas stet. CCZ_102

Bribiesca-Contreras, Guadalupe, Dahlgren, Thomas G., Amon, Diva J., Cairns, Stephen, Drennan, Regan, Durden, Jennifer M., Eleaume, Marc P., Hosie, Andrew M., Kremenetskaia, Antonina, McQuaid, Kirsty, O'Hara, Timothy D., Rabone, Muriel, Simon-Lledo, Erik, Smith, Craig R., Watling, Les, Wiklund, Helena & Glover, Adrian G., 2022, Benthic megafauna of the western Clarion-Clipperton Zone, Pacific Ocean, ZooKeys 1113, pp. 1-110 : 1

Molpadiodemas stet. CCZ_102

Fig. 35

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 4; 7.2701°N, 149.7827°W; 3552 m deep; 03 Jun. 2018; Smith & Durden leg.; GenBank: ON400708 (COI); NHMUK 2022.66; Voucher code: CCZ_102 .

Description.

Single specimen, ~ 32 cm long (Fig. 35A ). Body subcylindrical when alive, dorso-ventrally flattened in preserved specimen (L = 22 cm, W = 9 cm; Fig. 35E, F ), tapering distally; body wall is completely covered in sediment and globigerinas, firm, wrinkly, with transverse folds and ridges giving a partly serrated appearance to the margin; brim present; anus and mouth ventral (Fig. 35D, E ). Tube feet only visible on the ventral surface, cylindrical, and orange (Fig. 35C ). Dorsal surface is whitish and ventral is yellowish in preserved specimen, but heavily covered by sediment. Ossicles in tentacles; unbranched rods and branched rods, with branches intertwining at the ends creating irregular perforated mesh (Fig. 35B ).

Remarks.

COI sequence forms a clade with other species of Molpadiodemas including M. villosus ( Théel, 1886), M. morbillus O’Loughlin & Ahearn, 2005, M. crinitus O’Loughlin & Ahearn, 2005 and M. involutus (Sluiter, 1901). Closest is to M. morbilus (K2P 3.7-3.9%), and in the phylogenetic tree it is recovered in a well-supported clade with other species within the genus (Fig. 34 ), but species were not separated within the genus. Three species within the genus Molpadiodemas have been previously reported in the CCZ: M. altanticus (R. Perrier, 1898), M. villosus and M. helios O’Loughlin & Ahearn, 2005, with the latter species being recently described from the CCZ and so far not reported elsewhere ( O’Loughlin and Ahearn 2005). However, morphological characters of Molpadiodemas stet. CCZ_102 are not in accordance with the description of any of those three described species.

Ecology.

This specimen was collected on the sediment seafloor of a seamount in APEI 4 at 3552 m depth.

Comparison with image-based catalogue.

A very similar Molpadiodemidae morphotype (i.e., Molpadiodemas sp. indet., HOL_103) has been commonly encountered in seabed image surveys conducted across the eastern CCZ (e.g., Amon et al. 2017b) and in abyssal areas of the Kiribati EEZ, mostly in nodule field areas.

Figures

Figure 34. Phylogenetic tree of the class Holothuroidea. Concatenated (12 S, 16 S, 18 S, 28 S, COI, and H 3) median consensus BEAST tree with posterior probability (PP) and bootstrap (BS) values indicated. Only values of PP> 0.70 and BS> 50 are shown, with values of PP> 0.95 and BS> 90 indicated with a circle. Nodes not recovered on the RAxML tree are indicated with a hyphen. Sequences generated in this study are highlighted in violet.

Figure 35. Molpadiodemas stet. CCZ _ 102 A in situ image B tentacle ossicles C tube feet D dorsal surface E ventral surface of specimen before preservation. Scale bars: 2 cm (A); 20 μm (B); 1 cm (D, E). Image attribution: Durden and Smith (A); Bribiesca-Contreras (B, C); Wiklund, Durden, Drennan, and McQuaid (D, E).