Peniagone 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 : 219

Peniagone sp. MoV. 7321

Material examined. NMV F308228 * (1) [IN 2022 V 08 122] .

Diagnosis of IOT material. Single, elongated grey-cream specimen, up to 110 mm long (120 mm including tentacles), 30 mm wide and 15 mm high (preserved). Thin, semitranslucent skin with longitudinal muscles and mud gut content clearly visible (fig. 9a). White when preserved. Typical Peniagone shape, raised dorsally and with a slight convex curve to the ventral surface. Anus dorsal, terminal. Mouth ventral on short neck with approximately ten flaccid, extended tentacles. Anterior velum present but too damaged to assess. Tube feet all removed. Body wall with a mixture of cross and rod ossicles. Dorsal and lateral body wall with irregular spinous branched rods and low, flattened Peniagone -style crosses. Crosses ~200 μm in diameter with a smooth central beam, four arms flat to slightly curved and often irregular in shape and length, and with or without four short thick spinous vertical apophyses. Ventral wall also had smaller spinous primary cross ossicles, with smooth central beams, four (2–4) short apophyses, and irregular, “wiggly” arms of uneven length (fig. 9g, h). Irregular spinous rods also present (fig. 9k–m). Tentacle ossicles with smooth to spinous irregular crosses, variably with four short apophyses, or apophyses-free, and rods (fig. 9n–q). Crosses with apophyses in both smaller and larger forms, and apophyses-free crosses in smaller and larger forms. Rods straight, curved to strongly curved variably smooth to spinous.

Remarks. A combination of external and ossicle morphology, particularly the low crosses and unique small spinous primary crosses with uneven arms, make this specimen distinctly different from other IOT Peniagone examined. Ossicles not like Peniagone sp. MoV. 7320 above, and not a match for original illustrations for P. mus (Djakanov, 1952) or redescription by Kremenetskaia et al. (2021). Here we identify specimen to OTU level as Peniagone sp. MoV. 7321; additional review of literature is required before this specimen can be confirmed as a new species.

Distribution. This specimen lot only: Indian Ocean, Australian IOT, Cocos (Keeling) Islands Territory, Investigator Ridge Abyssal Stn. , 4980–4990 m.

References (for genus Peniagone ). Djakanov (1952), Hansen (1975), Kremenetskaia et al. (2021), Théel (1882).