Psychropotes dyscrita (Clark, 1920)

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

Psychropotes dyscrita (Clark, 1920)

Fig. 43

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 4; 7.0212°N, 149.9355°W; 5040 m deep; 02 Jun. 2018; Smith & Durden leg.; GenBank: ON400702 (COI); NHMUK 2022.83; Voucher code: CCZ_083 .

Description.

Single specimen, ~ 30 cm long (Fig. 43A ). Colouration of live specimen is yellow (Fig. 43A, B ), with reddish-light purple on ventral surface (Fig. 43C ). Tentacles 18, also reddish-light purple. Long, dorsal appendage with round end, slightly longer than the total body length, and developed very close to the posterior end of the body.

Remarks.

Gebruk et al. (2020) morphologically examined the specimen collected during the DeepCCZ and re-established the species Psychropotes dyscrita based on this specimen. The holotype was collected in Peru, at 5206 m depth, and the species is known from the Central Pacific Ocean at depths of 5040-5206 m ( Gebruk et al. 2020). Psychropotes dyscrita and P. moskalevi Gebruk & Kremenetskaia, 2020 are the two only known yellow species for this genus and were recovered as sister species (Fig. 34 ). The COI sequence for the DeepCCZ specimen is 1.1 ± 0.4% divergent (K2P distance) from specimens of P. moskalevi . Although this value seems low, the COI gene seems to be more conserved in the genus Psychropotes (1.1-13.4%, mean = 6.5%), with <2% interspecific divergence between some species pairs ( P. dyscrita - P. moskalevi , P. moskalevi - P. raripes Ludwig, 1893).

Ecology.

The specimen was found on the sediment seafloor of an abyssal plain in APEI 4 at 5040 m depth.

Comparison with image-based catalogue.

A very similar Psychropotes sp. morphotype (i.e., Psychropotes sp. indet., HOL_047) has been encountered in seabed image surveys conducted across nodule fields areas of the eastern CCZ (e.g., Tilot 2006), and in the Kiribati EEZ, where this taxon was the most abundant holothurian encountered ( Simon-Lledó et al. 2019d). In pioneer seabed image surveys conducted at the CCZ, prior to the re-establishment of the species ( Gebruk et al. 2020), this morphotype was typically classified as P. longicauda .Based on seabed imagery (e.g., without analysis of ossicles), it is not possible to determine whether HOL_047 specimens are P. dyscrita or P. moskalevi .

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 43. Psychropotes dyscrita (Clark, 1920). Specimen CCZ _ 083: A, B in situ images C lateral view D ventral view. Scale bars: 5 cm (A, B); 2 cm (C, D). Image attribution: Durden and Smith (A, B); Wiklund, Durden, Drennan, and McQuaid (C, D).