Enypniastes eximia Théel, 1882

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 : 229-231

Enypniastes eximia Théel, 1882

Enypniastes eximia Théel, 1882: 56–57 , pl. 8: 6–7. — Sluiter, 1901b: 77–79, pls. 2: 8–9, 5: 5. — Mitsukuri 1912: 215–218, pl. 7: 59– 60. — Heding, 1950: 118. — Pawson, 1976: 289, pl. 1a. — Pawson, 1982: 132, fig. 3a, c. — Ohta, 1985: 127–128. — Gebruk, 1989: 61–63, fig. 2: 6–7. — Miller and Pawson, 1990: 10–13, figs 1c, d, 4. — Bluhm and Gebruk, 1999: 181, fig. 6d. — Rogacheva et al., 2013: 611.— Gebruk et al., 2014: 165. — Wirawati and Setyastuti 2021: 464, fig. 5a, b.— Sigwart et al., 2023: 1–2, fig. 1. Enypniastes decipiens Koehler and Vaney, 1910: 95–96 , pl. 3: 1. Enypniastes globosa Hansen and Madsen, 1956: 58–59 , pl. 1: 4–5. Peniagone ecalcarea Sluiter, 1901a: 74–75 , pl. 10: 2. Enypniastes ecalcarea .— Heding 1950: 118, figs 1–4. Euryplastes obscura Koehler and Vaney, 1905: 71–72 , pl. 4: 7–9. Pelagothuria bouvieri Hérouard, 1906: 1–6 , fig. 2.— Hérouard, 1923: 94–99, pl. 6: 1. Planktothuria diaphana Gilchrist, 1920: 373–381 , figs 1–4. Enypniastes diaphana .— Billett et al. 1985: 400–403, fig. 2.

Material examined. NMV F296837 * (1) [IN 2021 V 04 005] ; NMV F296847 * (1) [IN 2021 V 04 013] ; NMV F308201 (1) [IN 2022 V 08 116] ; NMV F308208 (1) and NMV F308209 (1) [IN 2022 V 08 117] ; NMV F308331 (1) [IN 2022 V 08 195] .

Diagnosis of IOT material. Specimens fragile, gelatinous, and bulbous with a convex dorsal surface, flattened ventrally, wider anteriorly, and often translucent, with visible gut. IOT specimens reddish-brown to dark purple with a whiteish, translucent cover and up to 100 mm long and 35 mm wide ( NMV F308201 pre-preservation). Mostly light grey with some purple after preservation. Anus dorsal. Mouth ventral behind distinctive broad anterior cowl, up to 65 mm wide, made from a brim of fused tube feet, presenting as canal-like projections with processes at ends, often damaged, torn, and stringy in preserved specimens. Tentacles and canals in anterior cowl typically a darker maroon purple. IOT specimens are all damaged with few additional features, but when visible these include large leaf-like bifurcated tentacles, irregular dorsal papillae (fig. 14b), and two fin-like posterior lateral brims made from fused tube feet (fig. 14c). Ossicles, internal respiratory trees, and calcareous ring are all absent in this species.

Remarks. The previous six species of Enypniastes were all synonymised ( Gebruk, 1989) making E. eximia the only likely identification here. Descriptions of the type specimens ( Théel, 1882) and more complete collected specimens (e.g. Sluiter, 1901a; Wirawati and Setyastuti, 2021) include a typical body ratio of 1:2 (twice as long as wide), 12–14 canals in the anterior cowl, up to 20 leaf-like bifurcated tentacles, long dorsal papillae of varying number, and 8–15 fused podia creating the two fin-like posterior lateral brims. Some additional free lateral tube feet are noted in Sluiter, but Wirawati and Setyastuti note that tube feet are absent. Type specimens are 72 mm long and 32 mm wide, but species has been observed up to 250 mm in length ( Rowe et al., 2017). Despite damage, available morphology in IOT specimens matches previous reports, including ~1:2 body ratio, though occasionally more elongate. Based on 16S sequences, p-distances between samples here range from 2.3% to 6.6% (fig. S1). For Holothurians, this falls within the range of within-species divergence, so we are comfortable with identifying all specimens here as E. eximia .

Distribution. Cosmopolitan with global distribution including reports from as far north as the Aleutian Trench off Alaska, south to Antarctica, and from surface to hadal depths (6900 m Java Trench). Very common in north-east Atlantic.

Full bathymetric range. 0–6900 m (IOT 643–1991 m).

Type locality. South Pacific Ocean (off north-east New Zealand), 2030 m .

This species reported as widespread in Australia in AFD (January 2024) and recorded from surface to 2259 m in ALA (January 2024) including off Western Australia, New South Wales, Tasmania, and South Australia (Great Australian Bight). This IOT material agrees with worldwide distribution of the species .

References. AFD (2024), ALA (2024), Billett et al. (1985), Gebruk (1989), Gebruk et al., (2014), Miller and Pawson (1990), Rogacheva et al. (2013), Rowe, O’Hara and Bardsley in Byrne and O’Hara (2017), Sigwart et al. (2023), Théel (1882), Wirawati and Setyastuti (2021).