Oneirophanta mutabilis mutabilis Théel, 1879

Oneirophanta mutabilis mutabilis Théel, 1879 View in CoL

Oneirophanta mutabilis Théel, 1879: 6–7 View in CoL , figs 4–6; Théel, 1882: 62–68, pls. 21: 2, 22, 31: 1–3, 36: 1, 2, 8–11, 37: 4, 13, 38: 11, 12, 40: 1–3, 41: 1, 2, 4, 42: 9, 43: 1, 6, 45, 46: 6, 7.— Perrier, 1902: 374–380, pl. 18: 10–15.— Clark, 1913: 232.— Grieg, 1921: 5, pl. 2: 1, 2.— Hérouard, 1923: 39–40, pls. 4: 10, 5: 3, 4.— Ekman, 1927: 364–366, figs 1, 2.— Agatep, 1967: 63–65, pl. 10: 1–7.— Rowe et al., 2017: 480.

Oneirophanta mutabilis mutabilis View in CoL — Hansen, 1967: 485–488, figs 3, 4.— Hansen, 1975: 24–32, figs 2–6.— Gebruk et al., 2014: 165.— O’Hara et al., 2020: add. file 1: sup. table S1 (list).

Oneirophanta alternata Perrier, 1900: 117–118 View in CoL .— Perrier, 1902: 380–386, pls. 14: 3, 4, 18: 16–22.

Oneirophanta alternata var. talismani Perrier, 1902: 386–388 View in CoL , fig. 6.

Material examined. NMV F296855 About NMV * (2) and NMV F296858 About NMV * (1) [IN 2021 V04 028] ; NMV F308159 About NMV (2) [IN 2022 V08 105] .

Diagnosis of IOT material. Body robust, elongated, roughly cylindrical. Preserved specimens from IOT are large, up to ~ 24 cm long, 4.5 cm wide and 4.5 cm high ( NMV F296855, largest specimen, preserved). Strongly raised dorsally, flattened ventrally, and rounded to almost square at anterior and posterior ends. Colour orange to pink or white with darker brown or orange tips to tentacles and tube feet, but specimens white when preserved. Body wall firm, skin thick. Dorsal surface crowded with long (2.3–11.2 cm long), tapered, non-retractile papillae, making the body wall hard to see. Conspicuous, large (e.g. 3 cm long and 1 cm wide) ventrolateral tube feet in single to paired zigzag series along each side, rare smaller midventral tube feet. Anus terminal, ventral. Mouth terminal, ventral, with 15–20 feeding tentacles that never fully retract. Tentacle disc margins with rounded digit-like knobs but not ramified (branching) processes. Ossicles include perforated plates in various stages of development and variably branching rods and crosses, more concentrated in appendages. Perforated plates single layered with larger perforations at the centre and smaller towards the edge, sometimes with small vertical spines and rudimentary mesh forming, sometimes imbricating but not multilayered. As an ossicle size example for the larger IOT specimen NMVF 296855 noted above, plate diameter ~ 0.45–0.7 mm (dorsal), ~ 0.48–1.5 mm (ventral), 0.6–1.1 mm (papillae) and branching rods up to ~ 0.4 mm (tentacle) and ~ 0.46 mm (tube foot).

Remarks. Specimens here key morphologically to Oneirophanta mutabilis mutabilis using Hansen’s Galathea Report and descriptions, though he mentions ossicle plates with smaller vertical spines but never a secondary layer of meshwork ( Hansen, 1975). We note some very rudimentary mesh here, though agree there is no true multilayering. The original type description ( Théel, 1879) also noted that plates can be crowded or imbricating. One smaller specimen ( NMV F308159) had less typical rods and crosses, though plates were still present. Distinguished from Oneirophanta conservata Koehler and Vaney, 1905 by fewer ventrolateral tube feet but more ventrolateral papillae. Distinguished from O. setigera by the presence of perforated plate ossicles.Tentacles have clear marginal knobs, distinguishing them from O. mutabilis affinis . Both sequenced IOT O.mutabilis mutabilis samples form a highly supported clade within the COI phylogeny, with no previous O. mutabilis mutabilis available for comparison (fig. S5).

Distribution. Largely cosmopolitan.

Full bathymetric range. 1006–6000 m (IOT 2298–2850 m).

Type locality (as O. mutabilis ). Southern Indian Ocean (southeast of South Africa), 2515 m .

Subspecies not recorded for Australia in AFD or ALA (January 2024), but many O. mutabilis records were further identified to subspecies O. mutabilis mutabilis in the NMV catalogue, making the Australian range 1006–3853 m and extending the shallow limits of the previous known depth range (2515–6000 m). In Australia this species is now known from off the eastern coast (north-east Tasmania to the Coral Sea in Queensland), the Great Australian Bight in South Australia, and the Australian IOT.

References. ALA and AFD (2024), Bribiesca et al. (2022), Byrne and O’Hara (2017), Gebruk et al. (2014), Hansen (1975), O’Loughlin (1998).