Oneirophanta brunneannulata, Xiao & Zhang, 2024

Xiao, Yunlu & Zhang, Haibin, 2024, Three new species and one new record of Deimatidae (Echinodermata, Holothuroidea, Synallactida) discovered in the South China Sea and the Mariana fore-arc area using integrative taxonomic methods, ZooKeys 1195, pp. 309-335 : 309

Oneirophanta brunneannulata sp. nov.

Figs 4 , 5

Type material.

Holotype. IDSSE-2018-0612-HS01, collected from the continental slope of the South China Sea, station SY157-HS01 (18°51.18'N, 114°24'E), depth 1340 m, 1 Jul. 2019, preserved in -80 °C

Type locality.

On the continental slope of the South China Sea, depth 1340 m.

Diagnosis.

Body elongated, color reddish brown, with darker tentacles and tube feet. Mouth and anus ventral. Tentacle 20. Ventrolateral tube feet ~ 37 pairs, each tube foot end with a brown ring, arranged in alternating three rows, bilateral symmetry. Dorsal papillae 23-26 on each body side, arranged in single rows. Ventrolateral papillae 9-11 on each body side. Midventral tube feet two and rudimentary. Deposits perforated plates, rods of varying shapes and few spatulated crosses.

Description of holotype.

External morphology. Body elongated, dorsum convex, ventrum flattened. 20 cm long, and 5 cm wide before fixation (Fig. 4A, B ). Skin reddish brown, with darker coloration on tentacles and tube feet, a brown ring at the end of each tube foot. Tentacle 20, never with ramified processes, circum-oral papillae absent. Ventrolateral tube feet ~ 37 pairs, placed in alternating three rows, bilateral symmetry. Midventral tube feet two and rudimentary, one placed on half the body, the other placed on a rear quarter of the body, and several small tube feet surrounding anus. Dorsal papillae 23-26 on each body side, arranged in single rows along dorsal radii, measuring 5-6 cm. Ventrolateral papillae 9-11 on each side, arranged in single rows, comparatively shorter than dorsal papillae, measuring 2.3-4.6 cm.

Ossicle morphology. Dorsal deposits only robust perforated plates present (Fig. 5A1-A3 ), 0.6-1.1 mm in diameter, with central holes tapering from the center to the end, some perforated plates with irregular central apophysis (Fig. 5A1 ). Papillae contain (1) robust spatulated rods (Fig. 5B1-B3 ), 0.8-1 mm in length and partially connected at the ends (Fig. 5B1 ); (2) spatulated crosses (Fig. 5B4 ); (3) Perforated plates with 2-4 large central holes, rather slender than dorsal, measuring an average 0.9 mm in diameter (Fig. 5B5, B6 ). Tentacle deposits slender and sturdy rods with open ramifications (Fig. 5C ), 0.4-0.6 mm in length. Tube feet with varying types of rods: (1) slender rods with open ramifications, 0.5-0.7 mm long (Fig. 5D1 ); (2) smooth spindle-shaped rods without spines, 0.7 mm in length (Fig. 5D2 ); (3) sturdy spatulated rods (Fig. 5D1, D3, D4 ), with rudimentary or enlarged ends, 0.5-0.9 mm in length. Numerous amorphous shaped, irregular broken deposits on ventrum (Fig. 5E1, E2 ).

Etymology.

The specific epithet Oneirophanta brunneannulata in Latin means brown rings. It is here used as a noun in apposition and refers to the distinctive brown rings around the tube feet.

Distribution.

Only in the type locality.

Remarks.

Oneirophanta brunneannulata sp. nov. differs from other species in the genus in possessing brown rings at the end of tube feet that are arranged in three rows along ventrolateral radii. O. brunneannulata sp. nov. is relatively similar to O. mutabilis in possession of plates and spatulated rods, but there are differences: (1) different diameters of perforated plates, 0.6-1.1 mm in O. brunneannulata sp. nov., but 2-3 mm in O. mutabilis , and some perforated plates in O. brunneannulata sp. nov. possess a central apophysis. (2) different types of deposits in tube feet, O. brunneannulata sp. nov. has various forms of spatulated rods and a few spindle-shaped rods, but lacks perforated plates, and there are perforated plates in addition to sturdy and spatulated rods in O. mutabilis . O. brunneannulata sp. nov. differs from O. setigera in having perforated plates on the dorsum and the ventrum, lacked spatulated crosses, and had a large number of tube feet that were arranged in three rows. Larger central perforations on perforated plates were in papillae, and the presence of spatulated rods and papillae were arranged in single rows along the dorsal radius (double rows along dorsal radius in O. conservata ) distinguished O. brunneannulata sp. nov. from O. conservata (Table 2 ).

Figures

Figure 4. Oneirophanta brunneannulata sp. nov. (Holotype: IDSSE- 2018 - 0612 - HS 01) A dorsal view B ventral view. Scale bar: 6 cm.

Figure 5. SEM images of Oneirophanta brunneannulata sp. nov. (Holotype: IDSSE- 2018 - 0612 - HS 01) A 1 - A 3 dorsal body wall B 1 - B 6 papillae C tentacles D 1 - D 4 tube feet E 1 - E 2 ventral body wall. Scale bars: 300 μm.