Benthodytes marianensis Li, Xiao, Zhang & Zhang, 2018

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

Benthodytes marianensis Li, Xiao, Zhang & Zhang, 2018

Fig. 45

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 7; 5.1043°N, 141.8865°W; 4861 m deep; 25 May. 2018; Smith & Durden leg.; GenBank: ON400682 (COI); NHMUK 2022.82; Voucher code: CCZ_019 .

Description.

Single specimen (Fig. 45 ). Body is elongated, ~ 49.4 cm, dorso-ventrally flattened with flat ventral surface and inflated dorsal surface; anteriorly depressed and tapering posteriorly; colouration in live specimen is dark violet. Two irregular rows of large conical papillae running along the paired dorsal ambulacra.

Remarks.

The COI sequence is identical to the holotype of B. marianensis (K2P genetic distance = 0%) collected in the Mariana Trench at 5567 m depth ( Li et al. 2018). These two sequences are also recovered together in the phylogenetic tree (Fig. 34 ). The species is only known from this location. Morphological characters are also concordant with the original description, including an uncommon, very peculiar, cross-shaped, dorsal ossicle (Fig. 45B ).

Ecology.

The specimen was found on the sedimented seafloor of an abyssal plain in APEI 7 at 4860 m depth.

Comparison with image-based catalogue.

CCZ_019 resembles a Benthodytes sp. morphotype (i.e., Benthodytes sp. indet., HOL_111) encountered in seabed image surveys conducted across nodule fields areas of the eastern CCZ ( Amon et al. 2017b) and the Kiribati EEZ. However, the vivid dark/violet colouration of HOL_011 (contrasting with background bright sediment) can constrain the visibility of papillae features in in situ photographed specimens, potentially making these hard to differentiate from other Benthodythes sp. morphotypes in vertically-facing seabed imagery.

Family Elpidiidae Théel, 1882

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 45. Benthodytes marianensis Li, Xiao, Zhang & Zhang, 2018. CCZ _ 019: A in situ image B dorsal ossicles including peculiar cross-shaped ossicle C ventral ossicles. Scale bar: 5 cm (A); 100 µm (B, C). Image attribution: Durden and Smith (A), Kremenetskaia (B, C).