Psychroplanes Gebruk, 1988

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 : 219-222

Genus Psychroplanes Gebruk, 1988

Diagnosis. (translated from Gebruk, 1988). Body ovoid, length to width ratio ~2:1. Dorsally convex, body height equal to or exceeding body width. Dorsal ambulacral appendages include a velum and 1–2 pairs of small papillae behind this. Tube feet 5–10 pairs. Calcareous ring pieces with seven pairs of arms. Dorsal ossicles are crosses with well-developed apophyses. Number of apophyses varying: one central apophysis arising from centrum of the cross, and one apophysis on each of the arms can be present. Ventral ossicles also cross-shaped with varying number of apophyses.

Remarks. A rarely seen deep-sea genus known from mostly circumtropical and moderate latitudes. There are currently four accepted species of Psychroplanes worldwide, which had all been previously assigned to Peniagone ( Hansen, 1975; WoRMS, 2024). This genus was erected to account for ossicles unique within Elpidiidae , robust crosses with arms arising from a single central point rather than a central beam ( Gebruk, 1988). While the genus is not currently reported from Australia in ALA, Psychroplanes rigida (as Peniagone rigida ) was collected from the eastern Australian abyss off New South Wales in 2017 (NMV Catalogue, 2024). Four lots of Psychroplanes convexa are recorded here from the IOT voyages at depths of 2973– 4990 m. Diagnosis from translation of the original Russian (Antonina Kremenetskaia, pers comm., 2024).