Pseudostichopus hyalegerus (Sluiter, 1901) O'Loughlin & Ahearn, 2005

O'Loughlin, P. Mark & Ahearn, Cynthia, 2005, A review of pygal-furrowed Synallactidae (Echinodermata: Holothuroidea), with new species from the Antarctic, Atlantic and Pacific oceans, Memoirs of Museum Victoria 62 (2), pp. 147-179 : 170-171

Pseudostichopus hyalegerus (Sluiter, 1901) comb. nov.

Figures 10a , 12n–p

Meseres hyalegerus Sluiter, 1901a: 12 .— Sluiter, 1901b: 50–51, pl. 5 figs 2–4.— Perrier, 1902: 359.

Pseudostichopus trachus .— Mitsukuri, 1912: 3–9, pl. 1 figs 1–5.— Ohshima, 1915: 227–228.— Mortensen, 1918: 80–81, fig. 16 (non Pseudostichopus trachus Sluiter, 1901 ).

Pseudostichopus (Trachostichopus) tachimaruae Imaoka, 1978: 380–382 , fig. 2A–E, table 1–2 (synonymy by O'Loughlin, 2002).

Pseudostichopus (Trachostichopus) japonensis Imaoka, 1978: 382–384 , fig. 3A–D, table 1–2.— Imaoka, 1990: 148 (synonymy by O'Loughlin, 2002).

Pseudostichopus molpadioides Ohshima, 1915: 228–229 , pl. 8 figs 6a–c.— Heding, 1940: 353–359.— Imaoka, 1978: 384, tables 1, 2.— Imaoka, 1990: 152.— O’Loughlin, 2002: 304–305 (new synonym).

Pseudostichopus arenosus Ohshima, 1915: 229 .— Heding, 1940: 353–359.— Imaoka, 1978: table 1–2.— O’Loughlin, 2002: 304–305 (new synonym).

Material examined. Meseres hyalegerus Sluiter. Syntypes. Indonesia, Banda Sea, 5°28'S, 132°00'E, 204 m, Siboga stn 251, ZMA V.Ech. H9499 (1) ; ZMA V.Ech. H2177/1 (6) ; ZMA V.Ech. H21772/2 (1, mounted on glass in alcohol) .

Pseudostichopus (Trachostichopus) tachimaruae Imaoka. Holotype. Japan, W of Kyushu , near Shimo-Koshiki I., 400–450 m, T. Imaoka, 27 Oct 1976, SMBL 311 . Paratypes. Type locality, date, SMBL 312 (2).

Pseudostichopus (Trachostichopus) japonensis Imaoka. Holotype. Japan Sea , off the Akita Prefecture, 200–300 m, S. Nishimura, 1972–1973, SMBL 313 . Paratypes. Type locality and date, SMBL 314 (3).

Other material. North-west Pacific Ocean, Japan, 350–400 m, USNM 1025085 (3); 300–450 m, 1025086 (17); NMV F101861 (5); 420 m, 1071801 (1); Sagami Bay, 128–553 m, Northwest Pacific Expedition, Albatross stn 5092, USNM E17147 (42); NMV F101855 (5); stn 4968, USNM 1001645 (1); stn 5069, 1001646 (1); stn 5093, 1001647 (1); stn 5055, 1001648 (5); stn 5094, 1001649 (7).

Eastern Australian continental slope, Tasman Sea and Bass Strait , 293–1100 m, NMV F80171 – F80175 (21) , F80178 (3), F80181 (19), F80448 (1); 3300–3350 m, AM J23009 (1).

Description. Up to 120 mm long; typically encrusted with dense mat of predominantly sponge spicules, with shells and globigerines; frequently densely covered with tubular, thin, branched, tangled, epibiote; body dorsoventrally depressed, subacute margin; body wall semi-gelatinous, firm, translucent to opaque, wrinkled with pits and raised protuberances all over body; short papillae on paired radii, sparse irregular double series dorsolaterally, more numerous in band ventrolaterally; papillae cylindrical at base, tapering distally, typically 2.0 mm long, 0.3 mm diameter (at base); gonad tubules predominantly unbranched, rarely singly branched, rarely bifid distally; ossicles in tentacles, papillae, pygal lobes; tentacle ossicles irregular, frequently spinous, elongate rods, branching rare, up to 340 µm long; papillae with rare irregular rods up to 100 Μm long; papillae sometimes with “endplates”, very irregular perforated plates or irregular mesh of branched rods, up to 70 Μm wide; pygal lobe ossicles single, large, elongate, up to 800 Μm long, comprising dense perforated mesh of branched rods connected with open mesh, bluntly spinous marginally.

Colour. Body grey to off-white; papillae pale brown to off-white.

Distribution. West Pacific, Indonesia, Banda Sea, 204 m ( Sluiter, 1901a); Japan, Sagami Sea, 141–564 m ( Mitsukuri, 1912, as P. trachus ); Japan Sea, south of Honshu, 128–553 m ( Ohshima, 1915, as P. trachus ); 200–300 m ( Imaoka, 1978, as P. japonensis ); Hokkaido, Shiribeshi, 714 m ( Ohshima, 1915, as P. molpadioides ), Kyushu, Koshiki Is, 781 m ( Ohshima, 1915, as P. arenosus ); 400–450 m ( Imaoka, 1978, as P. tachimaruae ); eastern Australia, Tasman Sea and Bass Strait, 293–1100 m (this work).

Remarks. Eight of the eleven syntypes were present (Apr 2002) in the ZMA and examined. All were taken from the same locality, and the establishment of a lectotype is not necessary.

The characters of Meseres hyalegerus are consistent with the diagnosis of Pseudostichopus , and M. hyalegerus is reassigned to Pseudostichopus .

The types of Pseudostichopus molpadioides Ohshima, 1915 and P. arenosus Ohshima, 1915 cannot be located (see Introduction). The principal characters of Pseudostichopus molpadioides given by Ohshima (1915) are: up to 52 mm long; cylindrical form; pygal furrow; covered by sand, foraminiferans, some sponge spicules; 20 tentacles; tube feet in double rows on paired radii, most numerous ventrolaterally, up to 2.0 mm long; unbranched gonad tubules; irregular spiny ossicles perianally, up to 200 µm long; tube feet support rods up to 120 µm long, endplates up to 140 µm wide; lacking gonad ossicles. Ohshima (1915) considered that Pseudostichopus arenosus closely resembled P. molpadioides , the two species differing only in minor differences in the form of tentacle ossicles and absence of tube feet support rods in P. arenosus . In this study the detection of tube foot support rods in P. hyalegerus was not consistent, and the differing details of tentacle ossicle form in P. hyalegerus fell within the variations reported by Ohshima (1915). P. arenosus is considered here to be a junior synonym of P. molpadioides . The only characters distinguishing P. molpadioides from P. hyalegerus are the typical cover of predominantly sponge spicules in the latter, and possible differing form of perianal ossicles. The drawing of a perianal ossicle for P. molpadioides by Ohshima (1915) is identical with a fragment of the large perianal ossicles found in M. hyalegerus . A variation in body cover from predominantly to only some sponge spicules is considered here to be not diagnostically adequate for distinguishing the species. P. molpadioides and P. arenosus are thus junior synonyms of P. hyalegerus .

O'Loughlin (2002) considered P. tachimaruae and P. japonensis to be junior synonyms of M. hyalegerus , based on the descriptions by Imaoka (1978). The types were examined in this work, and the pygal lobe mesh ossicles unique to P. hyalegerus were found in paratypes of both P. tachimaruae and P. japonensis . The synonymies are confirmed here.

Amongst Pseudostichopus species, the distinguishing characters of P. hyalegerus are: encrusting mat of sponge spicules and other attachments; ossicles in the papillae and pygal lobes.

Figures

Figure 10. a, Pseudostichopus hyalegerus, sponge spicule cover (P. japonensis, paratype, SMBL 314, junior synonym, 29 mm long). b–c, P. mollis; b, rugose ventrum (TM H3111, 145 mm long); c, calcareous ring (TM H2004). d–e, P. papillatus (RAS, syntype, 27 mm long); d, dorsal view of paired radial tubercles; e, ventrolateral view, tube feet. f–h, P. peripatus; f, ventral view, marginal tubercles, grit attachment, transverse creases (NMV F101840, 60 mm long); g, ventral view, marginal tubercles, grit attachment, transverse creases (NMV F101839, 45 mm long); h, cylindrical muscles (arrows), gonad tubules (P. tuberculatus, holotype, OMNH Iv1190, junior synonym). i, P. tuberosus sp. nov. (USNM E16721, holotype, 115 mm long), ventral view, lateroventral tubercles (arrow).

Figure 12. Gonad ossicles (SEM). a–d, Meseres villosus (USNM E9929). e–f, M. translucens sp. nov. (USNM E48652, holotype). g–h, Pseudostichopus peripatus, g (USNM 12198), h (USNM E48638). i–l, P. tuberosus sp. nov. (USNM E16721, holotype). m, P. aemulatus (USNM 1025525, paratype). Posterior lobe ossicles (compound microscope). n–p, P. hyalegerus, n–o (NMV F80181), p (NMV F80178). Tentacle ossicles (compound microscope). q–t, M. ustulatus sp. nov. (NMV F101858, paratype).