Psolidium wongae Ong & O’Loughlin, 2019

Ong, Joo Yong, Wong, Helen P. - S., O, P. Mark & Loughlin, 2019, Two new tropical psolid sea cucumbers from the Strait of Johor, Singapore (Echinodermata: Holothuroidea) with a key to Psolidium species from the tropical East Indian-West Pacific region, Raffles Bulletin of Zoology 67, pp. 206-216 : 213

Psolidium wongae Ong & O’Loughlin , new species ( Figs. 6–10 )

Psolidium species a.— Ong & Wong, 2015: 275, Table 1.

Material examined. Holotype: ZRC.ECH.0299, Singapore, CMBS spec. no. JS-0569, stn. DW55, East Johor Strait , north east of Pulau Tekong , north of Tanjong Pasir River, collected by rectangular dredge, 1°25.003′ to 1°25.097′N, 104°05.049′ to 104°04.997′E, 11.6–13.0 m, laterite gravel and dead shells, coll. Bertrand Richer de Forges et al., 22 October 2012.

Description. Thick scales dorsally and laterally up to 2.0 mm wide, thin ventral sole; irregularly oval ventrally with slight taper towards anal end; body 22 mm long, 14 mm wide mid-body, 7 mm high mid-body. Slightly elevated orally, no cone, lacking oral valves, small papillae present; slightly elevated anally, no cone, lacking valves, small papillae present. Ten dendritic tentacles, eight large, two ventral small. Cucumariid-type ring; radial plates with anterior notch for longitudinal muscle attachment, notch posteriorly, lacking posterior prolongations; inter-radial plates tapered to an anterior point, posterior indentation. Up to four tube feet penetrate each scale dorsally and laterally, discs about 0.1 mm diameter. Margin of the ventral sole fluted/ribbed due to attachment to a scallop ( Pectinidae ) shell and with up to about 10 tube feet in a diagonal series along each fluted ridge in the mid-body, some tube feet between the ridges in the grooves; overall diagonal and not transverse fluting and tube feet series; lacking discrete outer series of smaller marginal tube feet at the edge of the sole; tube feet along mid-ventral radius in more scattered series, some on fluted ridges; ventral tube feet disc diameters about 0.2 mm.

Single polian vesicle. Gonad tubules not branched.

Multi-layered ossicles (scales) and small plates dorsally and laterally, lacking cups; multi-layered ossicles irregular in form and size, up to 1.9 mm long; plates smooth with lobed margins, not knobbed, irregularly oval in form and size, 3–11 perforations, 76–156 µm long. Sole with knobbed plates, variable in form and size, up to about 20 perforations, variably knobbed around margin and on surface, plates 91–192 µm long. Dorsal tube feet with elongate perforated support plates up to about 160 µm long. Ventral tube feet with elongate, perforated, variably knobbed, curved support plates, 129–312 µm long. Tentacles with rod plates, rods and rosettes; plates narrow, elongate, perforated, curved, irregular margins, 92–284 µm long; curved rods with short branches distally, smooth or with a few blunt knobs, up to about 170 µm long; rosettes predominantly oval, compact, up to about 60 µm long.

Live dorsal colour mottled with light and dark grey-brown predominantly on the lower sides, and white with pale and dark grey-brown over the apex; tube feet discs white. Preserved dorsal and lateral colour granular white (presence of surface plates) over grey-black. Preserved ventral sole white. Tentacles and introvert white with close grey-black flecking.

Distribution. Singapore: East Johor Strait, northeast of Pulau Tekong, north of Tanjong Pasir River, 11.6–13.0 m.

Etymology. Named wongae in appreciation of the generous, gracious, considerable and much appreciated supportive contribution of Helen Pei-San Wong (of the Tropical Marine Science Institute of the National University of Singapore).

Remarks. Psolidium wongae Ong & O’Loughlin , new species, is distinguished from all other tropical East Indian– West Pacific Psolidium species in the key above and by the following combination of characters: a low profile; tube feet series around the periphery of the sole up to about 10 wide; an absence of smaller outer marginal tube feet on the sole; an absence of cupped cross ossicles dorsally and ventrally.

Figures

Fig. 6. Dorsal view of live holotype of Psolidium wongae Ong & O’Loughlin new species, (ZRC.ECH.0299; 22 mm long preserved).

Fig. 7. Lower right, ventral view of live holotype of Psolidium wongae Ong & O’Loughlin, new species (ZRC.ECH. 0299; 22 mm long preserved), showing artificial fluted ridges; upper left. Pectinidae shell showing hard fluted ridges

Fig. 8. Lateral view of preserved holotype of Psolidium wongae Ong & O’Loughlin, new species (ZRC.ECH. 0299; 22 mm long preserved).

Fig. 9. SEM holotype ossicle views for Psolidium wongae Ong & O’Loughlin, new species (ZRC.ECH.0299). A, plates from dorsal body wall; B, scale from dorsal body wall, showing canals for tube feet.

Fig. 10. Ossicles of holotype of Psolidium wongae Ong & O’Loughlin, new species (ZRC.ECH.0299), as viewed through the light microscope. A. Multilayered scale ossicle from dorsal wall; B, plates from dorsal body wall; C, plates from sole; D, knobbed plates from sole; E, rod plates from sole tube feet; F, knobbed plates from sole tube feet; G, plates from sole tube feet; H, supporting rod plates from sole tube feet; I, rod plate from sole tube feet; J, endplate from sole tube foot; K, supporting rod plates from tentacle; L, rod plates from tentacles; M, rosettes from tentacle.