Psolus steuarti, Mackenzie, Melanie & Whitfield, Emily, 2011

Mackenzie, Melanie & Whitfield, Emily, 2011, An overview of the Australian psolid sea cucumbers (Echinodermata: Holothuroidea: Psolidae) with the description of 5 new species, Zootaxa 3037, pp. 21-36 : 33-35

Psolus steuarti sp. nov.

Table 1 , Figures 7 a–f.

Material examined. Holotype. Australia, Victoria, 38º28'41''S – 38º28'40''S, 149º34'48''E – 149º35'13''E, RV Southern Surveyor SS01/2000 stn 158, epibenthic sled 1426–1509 m, 17 Apr 2000, NMV F157398.

Remarks. Distribution for Ceto cuvieria taken from Australian Biological Resources Study (2011). Distribution ranges for Psolidium species follow O’Loughlin & Maric (2008). Distributions for Psolus salottii , Psolus springthorpei and Psolus steuarti are limited to single occurrences recorded for the type specimens so are not a true reflection of range at this stage. Habitats where recorded are a generalization only, based on collection data from material examined by O’Loughlin & Maric (2008), and by the authors for this paper.

Paratype. Type locality, depth and collection date, NMV F157399 (1) (damaged).

Description. Psolus species up to 27 mm long, 17 mm wide and 6 mm high (holotype, preserved); low profile raised and rounded orally with flattened oral opening rather than cone, tapered anally with slightly apical anal opening; tentacles 10, 8 large, 2 small ventrally; clear demarcation between body wall scales and 5 very distinct oral/anal valves, irregular sizes; coarsely granuliform dorso-lateral scales, typically off-white colouring with distinct white margins (preserved), up to 7 mm long covered with thick granules, ventral margin scales significantly smaller; sole with single outer peripheral series of distinctly small tube feet and larger inner series of zig-zag to irregular double rows of tube feet, bare mid-ventrally.

Large multi-layered ossicles (scales), up to 2.5 mm long dorso-laterally, also irregular shallow cups up to 64 µ m wide, rim finely knobbed with digitiform spines, and single-layered perforated plates up to 240 µ m long with surface and marginal knobs. Sole with thin, flat, perforated plates, irregularly curved at edges with fine knobs on margin and variably on surface, up to 272 µ m long by 240 µ m wide with up to 30 perforations. Tentacle ossicles consist of thick, curved, large and small perforated plates up to 360 µ m long with digitiform margins; curved, perforated support plates and smaller dendritic branch endplates ~72 µ m long also present.

Colour (preserved). Off-white.

Distribution. Australia, Victoria, 38º28'41''S – 38º28'40''S, 149º34'48''E – 149º35'13''E 1426–1509 m (type material only).

Etymology. Named for Frank Steuart in appreciation of his contribution to marine invertebrate research over three decades through fieldwork and leadership, as occasional president, with the Marine Research Group of The Field Naturalists Club of Victoria, and for his curatorial work on the molluscan collection in Museum Victoria.

Remarks. Psolus steuarti sp. nov. is distinguished morphologically from other Australian Psolus species by a combination of: thick granules on dorso-lateral scales; shallow, finely knobbed cups with digitiform margins present dorsally; and perforated knobbed plates in the sole.

Figures

FIGURE 7. Psolus steuarti sp. nov. holotype (a – c, NMV F 157398): a, dorsal view; b, lateral view (insert, thick granules); c, ventral view; paratype (d – f, NMV F 157399): d, sole ossicle; e, dorsal ossicles (multi-layered scales, perforated plates and cups); f, tentacle ossicles.

Tables

TABLE 1. Distribution of Australian species of Psolidae Forbes, 1841.

Species	Distribution	Depth range	Habitat
Ceto species
Ceto cuvieria (Cuvier, 1817)	Southeast of Flinders I., South Australia to Shark Bay, Western Australia	15–66 m	On sponge
Psolidium species
P. berentsae O’Loughlin & Maric, 2008	Queensland, Lizard I.	6–18 m	Under or among coral rocks and rubble
P. granuliferum H. L. Clark, 1938	SW Western Australia to SE Tas- mania	4–37 m	On coralline foliose algae, under rocks
P. hutchingsae O’Loughlin & Maric, 2008	Northern New South Wales	12–15 m	On rock, sponge, ascidians
P. karenae O’Loughlin & Maric, 2008	South Australia	3–12 m	Under or among rocks
P. laperousazi O’Loughlin & Maric, 2008	SE Tasmania to South Australia	1–10 m
P. m a r s h a e O’Loughlin & Maric, 2008	Western Australia to South Aus- tralia	5–14 m	On granite reef, under rocks, on coralline red algae, brown algae or sponge
P. mccallumae O’Loughlin & Maric, 2008	Western Australia, off Point Cloates	100 m	On hard substrate
P. minutum (H. L. Clark, 1938)	Eastern Tasman Sea	1–10 m	Under rocks, sandy bottom
P. nigrescens H. L. Clark, 1938	New South Wales, Broken Bay to Batemans Bay	0–11 m	Estuarine, mud sediment, on live and dead mussels
P. oloughlini sp. nov.	Tasmania, King I., Bass Strait,		Shallow sub-littoral zone
P. parmatum (Sluiter, 1901)	Indonesia to NW Western Austra- lia,	95–487 m	On coral sand, hard substrate and rubble
P. r a v u m Hickman, 1962	SE Tasmania to W South Austra- lia	0–15 m	Under rocks, littoral
P. spinuliferum (H. L. Clark, 1938)	NW Australia, Darwin to Perth	0–22 m	On coral rubble covered with sponges and algae, on mixed algal zone and reef flat under thin layer of sand
Psolus species
P. antarcticus (Philippi,1857)	Magellanic region of South America, South Georgia, Macqua- rie I.	100–1666 m
P. parantarcticus sp. nov.	Macquarie I.	108–135 m	Often attached to shells
P. salottii sp. nov.	South Australia and Southern Ocean north of Macquarie I. (sin- gle occurrences)	772–820 m and 400–600 m respectively
P. springthorpei sp. nov.	Queensland (single occurrence)	1330–1380 m	On rock, coarse sand and shell
P. s t e u a r t i sp. nov.	Victoria (single occurrence)	1426–1509 m