Synallactes stet. CCZ_153

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

Synallactes stet. CCZ_153

Fig. 39

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 4; 6.9704°N, 149.9426°W; 5009 m deep; 06 Jun. 2018; Smith & Durden leg.; GenBank: ON400714 (COI); NHMUK 2022.69; Voucher code: CCZ_153 .

Description.

Single specimen (Fig. 39A ). Body cylindrical, white, ~ 4 × as long as wide (L = 10 cm, W = 2.7 cm), flattened proximally and rounded distally; flattened ventral surface. Two rows, upper and lower, of lateral, small, conical, thin processes, similar to those around the proximal edge (Fig. 39D ). There is a row of yellowish, very small, tube feet in the mid-ventral surface, along the odd ambulacrum (Fig. 39E ). Skin firm but translucent. Colour on live and preserved specimen is white. Ossicles abundant on dorsal body wall, spatulated crosses only with a long spinous apophysis, end of arms spatulated with holes (Fig. 39B ). Ventral ossicles also spatulated crosses with a long spinous apophysis, smaller, sometimes with more than four arms, also spatulated ends of arms with holes (Fig. 39C ).

Remarks.

The closest matches for the barcoding gene COI sequence are published sequences from the genus Bathyplotes (89.9% similarity), also within the family Synallactidae . The sequence is distinct from the only sequence of Synallactes sp. (GenBank accession number: KX874365.1) included in the phylogeny (Fig. 34 ), and they were not recovered as a monophyletic group. The DeepCCZ specimen was recovered sister to species of Bathyplotes , with Synallactes sp. recovered separately from the other genera in the family Synallactidae , concordant with previous results ( Miller et al. 2017). Despite this, the specimen was assigned to the genus Synallactes based on external morphological characters that are concordant with those described from the genus. Species of Synallactes have previously been reported in the CCZ: Synallactes profundus (Koehler & Vaney, 1905) and Synallactes aenigma Ludwig, 1894; the latter being associated with manganese substrates. External morphology does not resemble to S. profundus .

Ecology.

This specimen was found on the sedimented seafloor of an abyssal plain on APEI 4 at 5008 m depth.

Comparison with image-based catalogue.

A very similar Synallactidae morphotype (i.e., Synallactes sp. indet., HOL_007) has been commonly encountered in seabed image surveys conducted across nodule field areas of the eastern CCZ (e.g., Amon et al. 2017b), but not in abyssal areas of the Kiribati EEZ, where synallactid specimens were very rarely encountered.

Family Deimatidae 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 39. Synallactes stet. CCZ _ 153 A in situ image B ossicles from dorsal skin C ossicles from ventral skin D dorsal view of specimen before preservation, E ventral view. Scale bars: 2 cm (A); 50 μm (B, C); 5 mm (D, E). Image attribution: Durden and Smith (A); Bribiesca-Contreras (B, C); Wiklund, Durden, Drennan, and McQuaid (D, E).