Molpadiodemas sp.

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 : 256

Molpadiodemas sp. MoV. 7329

Material examined. NMV F296854 * (1) [IN 2021 V04 026] ; NMV F308204 * (1) [IN 2022 V08 117] ; NMV F308263 * (2) [IN 2022 V08 143] .

Diagnosis of IOT material. Small, soft, dorsoventrally flattened, up to 35 mm long, 16 mm wide and 4 mm high ( NMV F308204, preserved). Gelatinous and translucent to cream-coloured with central cavity visible. Off-white to grey when preserved. Mouth ventral, with orange/brown to yellow tentacles. Anus ventral with pygal furrow. Lateral edges are wavy or bumpy rather than smooth and a darker cream-yellow pre-preservation. Tube feet small and filamentous, not restricted to paired radii, but more matted ventrolaterally. Partial covering of sand and forams. Lateral skin on preserved specimen is flattened completely to look brim-like against the central circular gut tube. Tube feet still visible all over though more concentrated ventrolaterally. Lateral edge is almost ridge-like with concentrated flattened tube feet. Ossicles in tentacles are smooth to irregular, straight to curved rods, many perforated or twisted, some curved rods with plate-like mesh, up to 176 μm, but typically 80–104 μm long.

Remarks. Specimens clearly group together based on pre- and post-preservation morphology. With thread-like tube feet they again key closest to Molpadiodemas villosus or M. porphyrus using O’Loughlin and Ahearn (2005). Ossicles with simple or mesh rods are like M. villosus here but differentiated from that species by being more dorsoventrally flattened, translucent and partially covered in sand, and from M. porphyrus by colour and form. Preserved flattened form and rod ossicles rather than true plates distinguish this specimen somewhat from Molpadiodemas sp. MoV. 7335, but additional morphological and phylogenetic work is required to further define the group. We identify these specimens here as OTU Molpadiodemas sp. MoV. 7329.

Distribution. These specimen lots only: Indian Ocean, Australian IOT, Christmas and Cocos (Keeling) Island Territories, Max Seamount Stn., Rudist Seamount Stn., and Cocos (Keeling) Stn., 1113–1990 m.

References. O’Loughlin and Ahearn (2005).