Zygothuria thompsoni (Théel, 1886)

Mackenzie, Melanie, Davey, Niki, Burghardt, Ingo & Haines, Margaret L., 2024, A report of sea cucumbers collected on the first dedicated deep-sea biological survey of Australia’s Indian Ocean Territories around Christmas and Cocos (Keeling) Islands (Echinodermata: Holothuroidea), Memoirs of Museum Victoria (Mem. Mus. Vic.) 83, pp. 207-316 : 249-250

Zygothuria thompsoni (Théel, 1886)

Holothuria thomsoni Théel, 1886a: 184–185 , pl. 10, figs 8, 11. Holothuria thomsoni var. hyalina Théel, 1886a: 185 . Mesothuria thomsoni (Théel, 1886) . — Östergren, 1896: 350–351. Zygothuria thomsoni (Théel, 1886) . — Gebruk et al., 2012: 331–

333, fig. 20, table 15. Zygothuria thompsoni (Théel, 1886) .— SolÍs-MarÍn, 2003: 277

(incorrect spelling).

Material examined. NMV F308198 * (2), [IN 2022 V 08 116] .

Diagnosis of IOT material. Elongate to oval specimens ~ 12 cm long x 4.2 cm wide, damaged, and atypically flattened or empty. Cream-coloured thin, wrinkled skin, but with some grey flecks and brown patches in places. Sole clearly defined by well-spaced series of tube feet on each ventrolateral margin, bare midventrally. No sign of dorsal papillae. Anus terminal. Mouth ventral to terminal. Small ossicle tables with predominantly three-armed pillars linked by two transverse beams and topped by three spires. Spires mostly broken but some indication that they are short compared with stem of pillar, and spinous. Bases typically ~240–290 μm, thick to thin, irregular with wavy edges and 12 or more elongate to oval or round perforations of varying size. No obvious placement of perforations based on size seen here. Rare thin, symmetrical hexagonal bases ~260 μm in diameter with six pentagon-shaped perforations (fig. 27f).

Remarks. Prominent tube feet on ventrolateral radii rather than tube feet scattered over entire body distinguish these specimens as Zygothuria not Mesothuria . Specimens key closest to Z. connectens or Z. thomsoni using Gebruk et al. (2012), but with ossicles a closer match to figures of Z. thomsoni (Théel, 1886) as redrawn in the same paper.

Distribution. Pacific Ocean, Indian Ocean (Australian IOT), (and as Z. thomsoni var. hyalina from southern Indian Ocean with limited confidence).

Full bathymetric range. 1991–5307 m (IOT 1957–1991 m).

Type locality. North-west and mid-north Pacific, 3375–5307 m.

This species not previously recorded from Australia in AFD or ALA (January 2024) .

This IOT material represents a geographic and bathymetric range extension for the species, previously only known from its type location, though with limited confidence.

References. AFD (2024), ALA (2024), Gebruk et al. (2012), SolÍs-MarÍn (2003).