Ophiocymbium cf. rarispinum Martynov, 2010

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

Ophiocymbium cf. rarispinum Martynov, 2010

Fig. 52

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 1; 11.2518°N, 153.6059°W; 5206 m deep; 10 Jun. 2018; Smith & Durden leg.; GenBank: ON400727 (COI); NHMUK 2022.73; Voucher code: CCZ_197 .

Description.

Single specimen, with white arms and greyish blue disc in situ (Fig. 52A ). Disc is flattened and somewhat pentagonal; brownish when alive and white after preservation (Fig. 52B, D ). Dorsal disc surface is covered by minute, thin, imbricated scales covered by a thin skin, not obscuring the scale margins; few granuliform spinelets scattered on the dorsal surface (Fig. 52B ). Small, oval, radial shields, approx. as long as wide, arranged diagonally and touching proximally; distal margin extends beyond the disc margin (Fig. 52D ). Ventral surface of the disc covered by scales similar to the ones on the dorsal surface, but lacking spinelets; gonads are visible through the thin scales (Fig. 52C ). Each jaw bears two or three apical papillae, and three oral papillae on each side; two distalmost are block-shaped while the third distalmost is spiniform. Oral shield is triangular, longer than wide, rounded proximally; separated from the first lateral arm plate by the wing-shaped adoral shield. Supplementary oral shield, wider than long, located on the distal margin of the oral shield. Two adoral shield papillae, with one placed in the middle of each shield, resembling arm spines in shape and size. Arms are slender, ≥ 3 × as long as the disc diameter. Dorsal arm plates triangular, with rounded distal margin and slightly convex distal edge, separated from preceding plates by lateral arm plates; first two dorsal arm plates absent but arm segments covered by thick skin with smaller plates embedded (Fig. 52D ). Adjacent lateral arm plates are slightly separated by soft tissue; each lateral arm plate bears four long arm spines, similar in size; only two arm spines present in the first three arm segments and three on subsequent two arm segments. First ventral arm plate is small, broad and triangular, with the rest being pole-axe shaped and separated from the preceding plate except for the first two segments. Tentacle pores are large throughout the entire length of the arm, with no tentacle scales except for the first arm segment, where there is one attached to the lateral arm plate and resembles a small arm spine.

Remarks.

In the phylogenetic tree, the specimen from the western CCZ is recovered as closely related to Ophiocymbium tanyae (Fig. 50 ). Ophiocymbium rarispinum was described from the Izu-Bonin Trench, between 6740 and 6850 m depth (ZMMU D-798), and no genetic sequences have been published. Morphological characters are concordant with the description of O. rarispinum , but differs in the length of the arms, the number of oral papillae and the number of arm spines.

Ecology.

The specimen was found crawling on the abyssal sediments of APEI 1 at 5206 m depth.

Comparison with image-based catalogue.

A similar Ophiuroidea morphotype (i.e., Ophiocymbium sp. indet., OPH_013) has been encountered in seabed image surveys conducted across nodule fields areas of the eastern CCZ, but not in the abyssal areas surveyed within the Kiribati EEZ.

Superorder Euryophiurida O’Hara, Hugall, Thuy, Stöhr & Martynov, 2017

Order Ophiurida Müller & Troschel, 1840 sensu O’Hara et al. 2017

Suborder Ophiurina Müller & Troschel, 1840 sensu O’Hara et al. 2017

Family Ophiopyrgidae Perrier, 1893

Figures

Figure 50. Phylogenetic tree of Ophiuroidea. Concatenated (28 S, and COI) 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 52. Ophiocymbium cf. rarispinum Martynov, 2010. Specimen CCZ _ 197 A in situ image B dorsal surface before preservation C detail of ventral surface, jaws and ventral arm plates D detail of dorsal arm plates. Scale bars: 1 cm (A, B); 5 mm (C); 2.5 mm (D). Image attribution: Durden and Smith (A); Wiklund, Durden, Drennan, and McQuaid (B-D).