Pseudostichopus mollis Théel, 1886

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 : 171-173

Pseudostichopus mollis Théel, 1886

Figures 1b, c , 9a, e , 10b, c , 11e, f

Pseudostichopus mollis Théel, 1886: 169–170 , pl. 10 figs 5, 6.— Ludwig, 1898: 7.— Perrier, 1902: 337–338.— Fisher, 1907: 691.— Ekman, 1925: 5, 28–36, figs 4, 5.— Ekman, 1926: 451–470, fig. Id.— Heding, 1940: 353–360.— Imaoka, 1978: table 1–1.— Imaoka, 1990: 148.— Gutt, 1991a: 147, 152, figs 3, 6, table 2.— Gutt, 1991b: 321, 324.— Thandar, 1992: 167.— Rowe, 1995: 285.— O'Loughlin, 2002: 304.

Pseudostichopus trachus Sluiter, 1901a: 15–16 .— Sluiter, 1901b: 52–53, pl. 5 fig. 1, pl. 8 fig. 8.— Perrier, 1902: 337–338.— Fisher, 1907: 693.— Ekman, 1925: 32–36.— Savel'eva, 1941: 74.— Djakonov, 1952: 127, 129.— Baranova, 1957: 239.— Djakonov et al., 1958: 366.— Imaoka, 1978: 384.— Cherbonnier and Féral, 1981: 383, 385, fig. 16.

Pseudostichopus nudus Ohshima, 1915: 230 .— Ekman, 1925: 32–36.— Heding, 1940: 353–359.— Djakonov et al., 1958: 367.— Rowe, 1995: 285 (as junior synonym of Pseudostichopus pustulosus ; non Pseudostichopus pustulosus Sluiter, 1901 ; new synonym).

Pseudostichopus (Trachostichopus) trachus .— Heding, 1940: 353–362, fig. 17.— Imaoka, 1978: table 1–2.— Thandar, 1992: 166.

Pseudostichopus (Pseudostichopus) dilatorbis Imaoka, 1978: 378–380 , 384, fig. 1 A–E, table 1–1 (part; paratypes non P. dilatorbis ; new synonym).

Pseudostichopus (Pseudostichopus) alatus Imaoka, 1990: 146–148 , fig. 1A–E (new synonym).

Meseres trachus .— Rowe, 1995: 285.— O'Loughlin, 1998: 497.— O'Loughlin, 2002: 300, 312, table 3 (new synonym).

Pseudostichopus pustulosus .— Rowe, 1995: 285 (non Pseudostichopus pustulosus Sluiter, 1901 ).

Material examined. Pseudostichopus mollis Théel, 1886 . Lectotype (designated here). Southern Pacific Ocean , off Chile, 52°45'S, 73°46'W, 448 m, Challenger stn 311, BMNH 2002.293 . Paralectotypes, type locality and date, 86.10.2.143 (3), 1956.10.3.6 (2); off Chile, 50°56'S, 74°14'W, 256 m, Challenger stn 309A, 86.10.2.142 (3); Southern Indian Ocean, off Marion I., 46°48'S, 37°49'E, 91–137 m, Challenger stn 144A, 86.10.2.144 (2).

Pseudostichopus trachus Sluiter, 1901 . Lectotype (designated here). Indonesia, Ceram Sea, 1°11'S, 130°09'E, 798 m, Siboga stn 161, ZMA V.Ech.H2496.2 (1). Paralectotype, Timor Sea, 8°50'S, 127°02'E, 883 m, Siboga stn 286, V.Ech.H2496.1 (1).

Pseudostichopus nudus Ohshima, 1915 . Neotype (designated here). North Pacific Ocean, Bering Sea, USA, Alaska, Aleutian Is , Bowers Bank , 54°33'N, 178°45'E, 1019–1068 m, RV Albatross, North-west Pacific Expedition, stn 4774, 4 Jun 1906, USNM E10787 . Same locality and date, 1008140 (4).

Pseudostichopus (Pseudostichopus) alatus Imaoka, 1990 . Holotype. Japan, Tosa Bay , 350 m, H. Horikawa, 30 Jan 1989, OMNH Iv1188. Paratype. Tosa Bay, 390–410 m, Iv1189 (1).

Other material. North Pacific Ocean , Bering Sea , Alaska, Bowers Bank, 1068 m, USNM E10697 (1) ; off southern California , W of San Nicolas I., 825 m , 32416 (19); off Oregon , 44°36'– 46°01'N, 124°40'– 124°45'W, 320–466 m, USNM E16503 (13) ; E16734– E16742 (20); E16745, E167446 (6); E16749– E16752 (9); E16886 (3); E16888 (16); E53270 (2); off San Diego, 572 m, E2042 (2); 762 m, E02035 (4); 379–636 m, E17014 (1); 914–969 m, E17016 (1); 1587 m, 32410 (3); Costa Rica, 245 m , 18269 (2).

South Pacific Ocean, south-eastern Australian continental slope, 460–1200 m , AM J16749 (1); J16836 (1); J20028 (2); J22248 (1); J22938, J22939 (3); J22943 (2); J22955 (5); J22957 (1); J22960 (7); J22964 (1); J22967– J22969 (9); J22972 (1); J22974, J22975 (6); J23218 (1); J23220 (1); J23268 (1) ; NMV F80176 , F80177 (2), F80179, F80180 (5) ; TM H3111 (1); H3114 (2); W of Cape Sorrell , 972 m , H2004 (2); Tasman Sea, Lord Howe Rise , 1920 m , NMV F97692 – F97694 (4); New Zealand, Campbell I., 589–594 m , USNM E48604 (2); Chatham Is , 964–1067 m , E48641 (1); Antipodes Is , 384–397 m , E48665 (7); off Chile, 960 m , 1002911 (2); Macquarie I., NMV F89907 (1); F85036 (4); 900 m , F89908 (1); Strait of Magellan , 485 m , USNM E48639 (3); 256–320 m , E48666 (25); 769–869 m, E48656 (7).

Antarctica, Palmer Archipelago , 460–500 m, USNM 1005855 (1) ; 460–500 m, 1008441 (2); Antarctic Peninsula , 500–670 m , 1005856 (1); 630–650 m, 1022611 (2).

Description. Up to 225 mm long; body rounded in transverse section, frequently flat ventrally, high convex dorsally; sometimes thick to thin, rounded, ventrolateral brim, especially anteriorly; pygal furrow sometimes barely evident in largest specimens; body wall leathery, firm, thick to thin; anterior middorsal soft inconspicuous madreporite; ventrally frequently rugose, wrinkled with pockets and fine transverse ridges, folds and protuberances sometimes evident along ventrolateral margin, sometimes with raised multilobed tubercles pygally or midventrally or in lateroventral series, tubercles sometimes surmounted by tube feet, ventrum frequently encrusted with globigerines; papillae most evident dorsolaterally in sparse radial band, frequently 2 up to 4 wide, strongly tapered, somewhat whip-like, up to 5 mm long (170 mm long specimen), frequently withdrawn or lost leaving pits; double series of ventrolateral tube feet rarely externally evident; minute tube feet ventrally, rarely evident; ossicles in tentacles, tube feet, perianally; tentacle ossicles numerous to sparse, irregular rods, typically 120–240 µm long, frequently swollen mid-rod, some thin branches, rare blunt spines, branches rarely connecting to create perforations, lacking mesh ossicles, rare large irregular tuber-like ossicles, up to 380 µm long; tube feet ossicles predominantly irregular, smooth, rarely branched rods, frequently with swelling mid-rod, typically 100–130 µm long; pygal lobes with small globular mesh ossicles, difficult to detect.

Colour. Body, tube feet pale brown to off-white; tentacles, longitudinal muscles dark brown to brown; gonad tubules, respiratory trees pale brown.

Distribution. Western Antarctica, Weddell Sea, 65°19'S, 56°48'W, 400 m ( Ekman, 1925); Weddell Sea, 340–470 m (Gutt, 1991); North and South Pacific Ocean, southern Indian Ocean, eastern Australian continental slope, Antarctic Ocean in Palmer Archipelago and off Antarctic Peninsula, 91–1587 m (this work).

Remarks. Théel (1886) listed “numerous” syntypes from Challenger stn 311. Six of these specimens (in three lots) were examined in the BMNH (Apr 2002), and one disintegrated specimen examined (Apr 2002) in ZMU (ZMA V.Ech.H2999). One of these specimens is designated as lectotype above. Théel (1886) also listed six specimens from stn 309A of which three were examined in the BMNH. Théel (1886) further listed two specimens from stn 144A, and both were present in the BMNH.

During an examination (Apr 2002) of holothurian types in the University of Amsterdam, a type specimen of Pseudostichopus trachus Sluiter was found to be registered as Pseudostichopus pustulosus (discussed above under M. pustulosus ). This specimen is designated the lectotype for P. trachus . O'Loughlin (2002) judged material referred to P. trachus by Mitsukuri (1912) and Ohshima (1915) to be M. hyalegerus , and raised doubts about determination of material as P. trachus by Heding (1940), Savel'eva (1941), Baranova (1957), Djakonov et al. (1958), and Cherbonnier and Féral (1981).

Significant features of the types of P. trachus are: large size, up to 180 mm long ( Sluiter, 1901b); slightly dorsoventrally depressed, flat ventrally, convex dorsally, pygal furrow, leathery wrinkled body wall, subacute pustulose margin with distinct small irregular protuberances; densely covered with globigerine attachments; tube feet all withdrawn, paired radial series ventrolaterally, small ones ventrally ( Sluiter 1901b), dorsal tube feet sparsely evident dorsally ( Sluiter, 1901b); cylindrical longitudinal muscles ("not round in cross section" according to Sluiter, 1901b), but seen here to be round but sometimes slightly flattened); long thin unbranched gonad tubules; "teeth" on posterior margin of radial plates of ring; tentacle ossicles irregular thick rods, sometimes branched, branches sometimes fused to create perforations, smooth or with large thorny spines, sometimes with central swellings, up to 200 Μm long; tube foot ossicles short smooth tapered rods, frequently with central swelling; body wall, gonads, respiratory trees lacking ossicles. The types were taken in Indonesia at 798– 883 m. In all respects, except the dorsal cover of globigerines and uncertain distribution of dorsolateral tube feet, P. trachus is indistinguishable from P. mollis . Many specimens of P. mollis have a dense ventral encrustation of globigerines, and quite wrinkled and pitted and ridged and pustulose ventrum and lateroventral edge. The presence of encrusting globigerines dorsally is considered to be not grounds for separating the species diagnostically. The various forms and sizes of the tentacle ossicles are noticeably similar for the P. mollis and P. trachus types, as are the teeth on the radial plates of the ring. The longitudinal muscles are cylindrical, and sometimes slightly flattened, in both species. The gonad tubules are uniquely long and thin and unbranched in both species. P. mollis is found on the Australian continentlal slope at depths similar to those of the P. trachus types. This study has shown that the degree to which the ventrolateral margin develops protuberances and serrations varies from strongly developed to non-existent within the same species such as in Pseudostichopus peripatus below. Similarly the ventrum may be relatively smooth or strongly pustulose with raised protuberances as observed here for P. mollis . P. trachus is thus judged here to be a junior synonym of P. mollis .

The “Type” for P. nudus nominated by Ohshima (1915), and given USNM Cat. No. 34150, cannot be traced (see Introduction). A neotype, selected from Ohshima’s original material, is designated above. P. nudus has all but one of the distinguishing characters of P. mollis : firm, leathery body wall; potentially large sac-like form; small tapered tube feet on the paired radii; cylindrical longitudinal muscles; very long unbranched gonad tubules, in series along gonoduct; tentacles with irregular rod ossicles; tube feet with small rod ossicles with central swellings; absence of gonad, respiratory tree, posterior lobe ossicles. Ohshima (1915) distinguished P. nudus by a midventral band of tube feet which were each surrounded by pustular protuberances. A prominent midventral band of tube feet arising from protuberances was seen in a number of specimens in this study, but other specimens showed a range of ventral conditions intergrading with P. mollis . Small tube feet are present ventrally in P. mollis , and in some specimens become evident and in some arise from irregular swollen protuberances. P. nudus is also considered here to be a junior synonym of P. mollis .

Rowe (1995) considered P. nudus to be a junior synonym of P. pustulosus . This synonymy is rejected above (see M. pustulosus ). Rowe (1995) identified material from off Newcastle on the eastern Australian slope as Pseudostichopus pustulosus . All Australian slope material has been examined and none determined as P. pustulosus . Material from off Newcastle (AM J16749) was determined as P. mollis . Ludwig (1894) referred material to P. mollis , but illustrated ( Ludwig, 1894, pl. 9 figs 5–9) ossicles from the genital tubules that are similar to those in the gonads of P. peripatus (see below). At least some of the material was not P. mollis , which consistently lacks gonad ossicles.

The two paratypes of P. dilatorbis have all the diagnostic characters of P. mollis , and are so assigned (see above).

The distinctive features of the two type specimens of P. alatus are: up to 115 mm long; pale brown to white, opaque body encrusted with sponge spicules, foraminiferans, shell, sand; 19 pale brown tentacles; tube feet on paired radii, more numerous ventrolaterally; very small tube feet ventrally; long thin unbranched gonad tubules in series along gonoduct; ossicles in tentacles only, not in gonads or tube feet; tentacle ossicles irregular rods about 150–400 µm long, frequently with fairly large spines, rare branching. The types of P. alatus exhibit all of the characteristics of P. mollis and P. trachus , and these observations are confirmed by the description of Imaoka (1990). P. alatus is considered here to be a junior synonym of P. mollis .

Amongst Pseudostichopus species, the distinguishing characters of P. mollis are: leathery brown body wall; typical absence of a dense cover of globigerines or sponge spicules; distinct papillae on the paired radii; absence of gonad ossicles.

Figures

Figure 1. Characters of pygal-furrowed Synallactidae. a, ventral mouth and anus (M. helios sp. nov., USNM E31104, paratype, 91 mm long); b, ventral peltate tentacles, polian vesicle (P. mollis, TM H2004; anterior end dissected off); c, respiratory tree (P. mollis, TM H2004); d, drawing of dorsal posterior pygal furrow; e, posterioventral view of pygal furrow and anus (M. violaceus, BMNH 86.10.2.150); f, anterior dorsal madreporite (arrow) (P. peripatus, USNM 1008159); g, drawing of calcareous ring (radial plate right, as in P. spiculiferus); h, calcareous ring (M. crinitus sp. nov., USNM E48644, paratype); i, calcareous ring (M. violaceus, BMNH 86.10.2.145).

Figure 9. Characters of Pseudostichopus. a, drawing of transverse section of mid-body (as in P. mollis); b, cylindrical longitudinal muscles detached from calcareous ring (P. tuberosus sp. nov., NMV F101864, paratype); c, dorsolateral radial papillae (P. elegans, NMV F97447, papillae up to 8 mm long); d, drawing of part of gonad, unbranched tubules, arising separately along gonoduct; e, two series of unbranched gonad tubules along gonoduct (P. mollis, TM H2004); f, gonad (P. tuberosus sp. nov., paratype, USNM 1008333).

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 11. Tentacle ossicles (SEM). a–b, Pseudoshichopus aemulatus (USNM 1025525, paratype). c–d, P. elegans (USNM E16505). e–f, P. mollis (USNM E48656). g–h, P. tuberosus sp. nov. (USNM E16721, holotype). i–l, P. peripatus, i (USNM 12198), j (USNM E38794), k (USNM E38796), l (USNM E49349).