Psychropotes depressa ( Théel, 1882 )

Psychropotes depressa ( Théel, 1882) View in CoL

Euphronides depressa — Théel, 1882: 93–96, pls. 26, 35: 5–6, 40: 7, 46: 4. — Ohshima, 1915: 244–245, fig. 1. — Ohshima, 1916–1919, with 3 figs.

Psychropotes depressa View in CoL .— Hansen, 1975: 106–111, figs 43–44. — Gebruk, 2008: 50, 51; Rogacheva et al., 2013: 599, fig. 17f, g. — Gebruk et al., 2014: 160–161.

Euphronides depressa var. minor Théel, 1886b: 2 View in CoL .

Euphronides cornuta Verrill, 1884: 217 View in CoL . — Verrill, 1885: 518, 538, figs 32–33. — Deichmann, 1930: 127–128. — Heding, 1940: 368.

Euphronides tanneri View in CoL — Ludwig, 1894: 39–44, pls. 3: 7, 4, 5: 17–19.

Euphronides auriculata Perrier, 1896: 901–902 View in CoL . — Perrier, 1902: 434–438, pls. 13: 1–2, 20: 12–13. — Grieg, 1921: 8–9.

Euphronides violacea Perrier, 1896: 902 View in CoL . — Perrier, 1902: 438– 441, pl. XX: 14. — Deichmann, 1930: 128–129. — Deichmann, 1940: 201–202. — Heding, 1942: 15–16. — Madsen, 1947: 16. — Deichmann, 1954: 384.

Euphronides talismani Perrier, 1896: 902 View in CoL . — Perrier, 1902: 441– 444, pl. XX: 15. — Hérouard, 1902: 30–31, pl. II: 19–22. — Deichmann, 1930: 129. — Heding, 1942: 15, fig. 15.

Benthodytes assimilis Théel, 1886b: 2–3 View in CoL .

Material examined. NMV F296865 About NMV * (2) [IN 2021 V 04 033] ; NMV F296881 About NMV * (1), [IN 2021 V 04 050] ; NMV F308148 About NMV * (1) [IN 2022 V 08 105] ; NMV F308194 About NMV (2) and NMV F308195 About NMV (2) [IN 2022 V 08 115] .

Diagnosis of IOT material. Medium to large violet specimens up to ~ 255 mm long, 45–75 mm wide and 50 mm high ( NMV F308195, preserved, widest at anterior brim). Unpaired, flaccid dorsal appendage, tapering from a wider base to narrow rounded tip, variable in size, approximately one quarter to one seventh of the length of the body in preserved specimens. Dorsal appendage placed at variable distance from the posterior end of the body, but typically one third of a body length from the end. Skin soft and smooth to wrinkled, thin dorsally, usually thicker ventrally. Light purple and pink dorsally, often with darker patches or sometimes semitransparent showing gut contents. Darker purple to rust-red around brim, tentacles, tube feet, and often ventrally. Body form elongate, dorsally raised, ventrally flattened, surrounded by a narrow to very broad brim of enclosed tube feet, sometimes with free filamentous tips, brim often wider anteriorly. Anus ventral, terminal (under brim). Mouth ventral. 18 retractile tentacles, rounded with marginal knobs on discs. Midventral tube feet present throughout nearly entire length of sole, semi-retracted, small to medium and conical, in paired to zigzag row. Up to four pairs of reduced (e.g. <5 mm) dorsal papillae ( NMV F308194, NMV F308195), but otherwise inconspicuous or retracted to bumps. Dorsal body wall ossicles are cross-shaped with four arms and one smooth central spine-like apophysis. Arms with gentle to strong curve, length variable (e.g. 136– 429 μm), distally spinous but with one or more additional vertical spines and occasionally some extra serrations projecting from the dorsal surface before the arm curves. Rarely a lot more spinous, with spines projecting from both dorsal and ventral surfaces (fig. 19g). Papillae ossicles similar. Ventral ossicles rods (e.g. 320–440 μm) and rare reduced crosses. Tentacles with straight to curved rod ossicles (e.g. 400–528 μm), spinous at ends and occasionally branching.

Remarks. Specimens resembled the original ( Théel, 1882) and Galathea Report ( Hansen, 1975) descriptions for Psychropotes depressa , and keyed closest to that species based on external morphology and ossicles, however placement and measurements for the dorsal appendage were more variable in IOT specimens. Two specimens, NMV F296881 and NMV F308148 (fig. 20k– m) were both bulbous and full of mud, with stretched, thin skin, and very tapered and narrow at the anterior once preserved. NMV F296881 was quite damaged and missing its dorsal appendage once preserved. Genetics (fig. S1) confirm these specimens fit with other IOT P. depressa , and both morphologies are shown in the accompanying figures.

Distribution. Cosmopolitan. *

Full bathymetric range. 957–4200 m * (IOT 2289–3100 m).

Type locality. North Atlantic Ocean (south of Portugal), 1993– 2515 m .

*Reported from Atlantic and Pacific to 4200 m by Rogacheva et al. (2013), but as cosmopolitan to 4060 m by Gebruk et al. (2014). Hansen (1975) is a mix of both.

This species previously recorded for Australia in AFD (Lord How Rise) and from the eastern coast of Australia off Bermagui in NSW to the Coral Sea in Queensland at depths of 1761– 2902 m in ALA (January 2024). This IOT material represents a geographic and bathymetric range extension for the species in Australia and new record for the Indian Ocean (no records for this region on the Ocean Biogeographic Information System [ OBIS], January 2024) .

References. Gebruk et al. (2014), Hansen (1975), OBIS (2024), Rogacheva et al. (2013), Théel (1882).