Psolus parantarcticus, 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 : 28

Psolus parantarcticus sp. nov.

Table 1 , Figures 4 a–f.

Material examined. Holotype. Australia, Macquarie I., off Nuggets Point, 54°33.4'S 158°56.9'E, 108–135 m, ANARE, MV Nella Dan, Cochrane, T., 8 Dec 1986, NMV F60306 .

Paratypes. Type locality and date, NMV F176181 (1), NMV F160012 (4).

Other material. Australia, Macquarie I., 54°S 159°E, USNS Eltanin, 1968, USNM E33625 (1); Australia, Macquarie I., 112–124 m, USNS Eltanin, 1974, USNM E33647 (2).

Description. Psolus species up to 45 mm long, 31 mm wide, 12 mm high (damaged paratype NMV F176181, preserved); oval to round in form with low profile, slightly raised anteriorly; clear demarcation between the body wall scales and oral and anal openings which are both concave when tentacles are retracted; tentacles 10, 8 large, 2 small ventrally; 5 medium-sized oral valves, sometimes composite, with small body wall scales encroaching up to half the length, both scales and valves are granuliform; large, irregular dorso-lateral scales up to 9 mm long with finely granuliform ‘beaded’ surface and typically grey to pale brown colouring with distinct white margins (preserved); 4 to 5 clearly defined rows of significantly smaller scales on the ventral margin, less than 1 mm in length, often conspicuous due to their central darker brown colouring; sole with inner paired to single or zig-zag rows of larger tube feet and a peripheral band of closely placed, smaller tube feet, bare mid-ventrally but tube feet extend variably at oral and anal ends onto the mid-ventral line.

Dorsal and lateral ossicles consist of multi-layered plates only, up to 1.68 mm long. Sole ossicles consist of oval to rounded bowls up to 160 µ m long and 128 µ m wide with heavily knobbed raised margins and rarer central knobs, rounded perforations are typically smaller towards the edges with 2–3 larger central perforations up to 48 µ m wide; knobbed perforated plates up to 160 µ m long and 120 µ m wide sometimes present. Majority of tentacle ossicles are thin, curved, irregular perforated plates with bluntly spinous edges; largest tentacle ossicles are thick and triangular, slightly curved with surface knobs and up to 424 µ m long and 256 µ m wide.

Colour (preserved). Pale to dark brown or grey dorso-lateral scales with distinct white margins.

Distribution. Australia, Macquarie I.; 108– 135 m.

Etymology. From the Latin par (like), with reference to its superficial similarity to P. antarcticus .

Remarks. Psolus parantarcticus sp. nov. was initially assumed to be P. antarcticus , which is also present on Macquarie Island at similar depths. Closer examination of preserved specimens revealed significant differences including encroaching body wall scales on oral valves for P. parantarcticus , along with bowl-like ossicles in the sole and multi-layered ossicles only dorso-laterally. P. parantarcticus is distinguished from other Australian Psolus species by a combination of: close peripheral series of distinctly smaller ventral tube feet; finely granuliform ‘beaded’ body wall scales; bowl-shaped sole ossicles; multi-layered ossicles only dorso-laterally.

Figures

FIGURE 4. Psolus parantarcticus sp. nov. holotype (a – b, NMV F 60306): a, dorsal view; b, dorsal view (oral end, anal end); paratype (c – f, NMV F 176181): c, lateral view; d, ventral view (insert, smaller close series of marginal tube feet); e, bowl-like sole ossicle; f, tentacle ossicles.