Psolidium aequm, Davey, 2013

Davey, Nicola, 2013, The Psolidae of New Zealand and some additions to the Macquarie Ridge fauna (Echinodermata: Holothuroidea: Psolidae), Memoirs of Museum Victoria 70, pp. 51-67 : 60-62

Psolidium aequm sp. nov.

http://zoobank.org/urn:lsid:zoobank.org:act:3EC47623-6ED4-

442B-887C-C4454A26A2A1

Table 1, Figures 2, 5A–B, 8A–H.

Material examined. Holotype. New Zealand, Hikurangi Margin: NIWA 68136 (1) Stn SO 191-2/138, 41.78°S 175.40°E, 1043–1059 m, RV Sonne, 18/02/2007.

Paratypes. NIWA 32023 (29), same as holotype locality and date.

Other material. Hikurangi Margin: NIWA 26413 (8) Stn TAN0616/79, 41.78°S 175.39°E, 1040–1053 m, 13/11/2006; NIWA 26414 (7) Stn TAN0616/83, 41.78°S 175.39°E, 1050–1053 m, 13/11/2006; NIWA 32259 (37) Stn SO191-2/149, 41.78°S 175.40°E, 1055 m, 19/02/2007; NIWA 34955 (9) Stn TAN0616/79, 41.78°S 175.39°E, 1040–1053 m, 13/11/2006.

Description. Psolidium species up to 10 mm long, 5.5 mm wide, 5 mm high. Profile moderately low, anal and oral ends commonly raised, no discrete oral or anal valves or plates. Dorsal and lateral scales continuous over body wall, up to 1.5 mm wide, decreasing in size towards the ventral sole. Scales orally and anally smaller, less granular than other scales and paler in colour; dorsal and lateral scales brown, with a 0.25 mm pale grey to white margin; scales on ventral margin up to 0.5 mm wide and lighter in colour, imbricate. Dorsal and lateral tube feet small, inconspicuous, few visible. Tentacles 10, 8 + 2 (ventral smaller). Sole naked midventrally, peripheral series of closely set large tube feet in a single row, sometimes extending onto midventral radius anteriorly and posteriorly; no complete outer series of small peripheral tube feet but on some specimens few smaller tube feet scattered around ventral margin.

Dorsal and lateral ossicles large multilayered perforated plates (scales) with tube feet holes, sometimes with marginal thickening, secondary layering and anastomosing towards outer margins, up to 1580 µm wide with small inconspicuous tube foot canals up to 45 µm wide; large thick, single-layered plates up to 120 µm long with a smooth surface; tube foot support plates thin, rare (due to few dorsal or lateral tube feet) single-layered plates, curved, variably smooth or finely knobbed and relatively curved, up to 80 µm long and with up to 8 perforations. Ventral ossicles flat to slightly curved single-layered perforated plates up to 125 µm long, one side of plates knobbed, other side completely smooth, commonly with 4 perforations (up to 13). Perforations mostly uniform in size but sometimes a few smaller marginal perforations present; margin of plates sharp and angular. Tentacle ossicles long, thick rods, sometimes perforated at either end, less commonly perforated in the middle, rods up to 300 µm long, variable in shape, from straight to curved, rarely with a ‘bend’ centrally but most commonly with a slight curve, blunt spines sometimes present on either side of centre, sometimes a cluster of perforations at the end of a rod. Smaller single-layered perforated plates, up to 80 µm long, perforations inconsistent in size, shape and arrangement, ranging from flat to curved.

Colour. Preserved: pale to dark brown with grey, light brown or white margins around dorsal and lateral scales. Tentacles brown.

Distribution. New Zealand, Hikurangi Margin, 1040–1059 m.

Etymology. The species name is Latin, meaning equal, to reflect the characteristic regular perforations in the ventral ossicles.

Remarks. Psolidium aequm sp. nov. differs from other Psolidium species by a combination of the ventral ossicles having predominantly four (sometimes more) uniform perforations, the presence of a few outer ventral peripheral tube feet, the presence of tentacle rod ossicles, commonly with perforations through the middle as well as blunt spines on either side of the middle.