Molpadiodemas involutus (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 : 160-161

Molpadiodemas involutus (Sluiter, 1901) comb. nov.

Figures 3m –o , 4u–x

Meseres involutus Sluiter, 1901a: 11–12 .— Sluiter, 1901b: 49–50, pl. 8 fig. 6.— Perrier, 1902: 359. ( Meseres convolutus ) [lapsus].— O'Loughlin, 2002: 306, fig. 2e, tables 1, 3, 4.

Pseudostichopus globigerinae Hérouard, 1923: 23–25 , pl. 4 fig. 6.— Mortensen, 1927: 386–388.— Deichmann, 1930: 87, 90.

Pseudostichopus (Pseudostichopus) globigerinae .— Heding, 1940: 353–360.— Imaoka, 1978: table 1–1.— Thandar, 1992: 167.

Pseudostichopus villosus .— Hansen, 1956: 47–48 (part; non Pseudostichopus villosus Théel, 1886 ).

Pseudostichopus (Pseudostichopus) dilatorbis Imaoka, 1978: 378–380 , 384, fig. 1 B–E, table 1–1 (new synonym).

Meseres globigerinae .— O’Loughlin, 2002: 305, tables 1, 3 (new synonym).

Material examined. Meseres involutus Sluiter. Lectotype (designated here). Indonesia, Sawu Sea, 10°49'S, 123°23'E, 918 m, Siboga stn 300, ZMA V.Ech.H1052. Paralectotype. Seram Sea, 3°27'S, 131°01'E, 567 m, Siboga stn 173, ZMA V.Ech.H1051 (1).

Pseudostichopus globigerinae Hérouard, 1923 . Lectotype (larger syntype, with pygal furrow, designated here). North Atlantic , off Newfoundland, 46°18'N, 50°42'W, 4380 m, Monaco stn 2964, 20 Jul 1910, MOM (examination via pers. comm. by M. Bruni at MOM). Second syntype, type locality and date, MOM.

Pseudostichopus (Pseudostichopus) dilatorbis Imaoka, 1978 . Holotype. Japan, W of Kyushu , near Shimo-Koshiki I., 400–450 m., SMBL 309 .

Other material. Pacific Ocean , eastern Australia, Tasman Sea, Lord Howe Rise, 1423 m, AM J23326 (1) ; off Newcastle , 2984–3058 m, J16833 (1); off Nowra, 1650–1750 m, NMV F80451 (1) ; Japan, East China Sea, off Kagoshima, 420 m, USNM 1071585 (3) , NMV F104793 (2) ; 300–330 m, USNM 1071802 (1) ; Galapagos , 3667 m, USNM E950 (1).

Atlantic Ocean, West European Basin, 4426–4435 m, USNM 1005340 (8) ; NMV F101850 (2); off South Carolina, 2100 m , USNM E41392 (3) ; NMV F101851 (1); Gulf of Mexico, 1668 m , USNM E46796 (3); off Louisiana, 2063–2085 m , USNM 1008165 (2) ; NMV F101869 (1); 1829 m , USNM E46798 (2); 1646 m , E46799 (1).

South Atlantic Ocean , Argentina, Buenos Aires, SE of Mar Del Plata, 5208–5223 m, USNM 1005317 (1) ; 1008207 (1); off Falkland Is, 5687–5801 m, E49256 (5); E49359 (1); Scotia Sea, 2250–2404 m, E49295 (2).

Description. Up to 155 mm long; typically encrusted with globigerine or small stone attachments; body usually dorsoventrally depressed; flat ventrally, low convex dorsally; margin subacute, partly serrated because of transverse creasing of body wall, sometimes narrow rounded brim; body wall thin to thick, firm, wrinkled, with small digitate projections on low reticulate ridges; raised protuberances ventrolaterally, pygally; close cover of thin cylindrical tube feet, sometimes larger and more evident and reddish-brown in ventrolateral band, sometimes matted, typically 1.0 mm long, 0.2 mm diameter, up to 3.0 mm long, 0.5 mm diameter; multiple branching gonad tubules; ossicles in tentacles only, sometimes not detected; ossicles unbranched rods with thick central swelling and branched rods, branches frequently intertwining at ends or joining laterally to create irregular perforated mesh, ossicles up to 330 Μm long.

Colour. Body grey to off-white; tube feet sometimes reddish-brown ventrolaterally.

Distribution. Indonesia, Seram and Sawu Seas, 567–918 m ( Sluiter, 1901a); eastern Australia, Tasman Sea, 1423–3058 m ( O’Loughlin, 2002); Japan, W of Kyushu, 400–450 m ( Imaoka, 1978; as P. dilatorbis ); East China Sea, off Kagoshima, 300–420 m (this paper); Galapagos Islands, 3667 m (this paper); northern Atlantic Ocean, off Newfoundland, 4380 m ( Hérouard, 1923, as P. globigerinae ); West European Basin, 4426–4435 m; western Atlantic Ocean, off South Carolina, Gulf of Mexico, 1646–2100 m; southern Atlantic Ocean, off Argentina, 5208–5223 m; Falkland Is, 5687–5801 m; Scotia Sea, 2250–2404 m (this paper).

Remarks. Sluiter (1901a) described two syntypes, and both were examined during a visit to the University of Amsterdam (Apr 2002). One is designated above as the lectotype.

Hansen (1956) considered P. globigerinae to be a junior synonym of P. villosus . O'Loughlin (2002) rejected the synonymy on the evidence that P. villosus never has tufts of tube feet on tubercles along the posterior margin, or a globigerine cover, or translucent body wall. A further synonymy was not suggested. Based on the description by Hérouard (1923), on observations communicated by Michèle Bruni (MOM), and on photographs by Francisco Solis-Marin (UNAM) of a tentacle ossicles slide prepared by Gustav Cherbonnier (MNHN box 108 slide 44), the characters of the larger syntype are: up to 30 mm long; body completely covered by globigerines; body wall thin, soft, translucent; pygal furrow present; villous-like cover of unequal and unevenly distributed small tube feet, rare midventrally, in tufts on posterior ventrolateral tubercles creating serrated appearance; flat longitudinal muscles; lacking gonad; and tentacle ossicles branched closed mesh fragments. O’Loughlin (2002) noted that there was inadequate descriptive information to confirm any synonymy, but in the light of further data P. globigerinae is considered here to be a junior synonym of M. involutus .

Hérouard noted that there was no pygal furrow on the 15 mm long smaller syntype of P. globigerinae , and M. Bruni observed a cylindrical longitudinal muscle. The smaller of the two syntypes is not conspecific with P. globigerinae , but cannot be identified. The larger syntype is designated above as lectotype.

The description of P. dilatorbis by Imaoka (1978) refers to the external characters of the large paratypes and the internal characters of the holotype. The holotype has the diagnostic characters of Molpadiodemas ; the paratypes those of Pseudostichopus . Although the holotype lacks tentacles ossicles, several specimens of Pseudostichopus dilatorbis recently donated by Tohru Imaoka yielded abundant tentacle ossicles and possess external characters similar to those of M. involutus . Pseudostichopus dilatorbis is considered here to be a junior synonym of Molpadiodemas involutus . The two paratypes of P. dilatorbis are much larger (up to 180 mm long) than the holotype, and are very close in appearance and diagnostic characters to the types of Pseudostichopus trachus Sluiter, 1901 , which is considered below to be a junior synonym of Pseudostichopus mollis . The paratypes are referred below to P. mollis .

Material determined here extends the distribution of M. involutus from the western Pacific Ocean into the eastern Pacific Ocean, northern and southern Atlantic Ocean and Scotia Sea.

Amongst Molpadiodemas species, the distinguishing characters of M. involutus are: body wall with small digitate projections on low reticulate ridges; margin partly serrated because of transverse creasing of body wall; cylindrical tube feet most evident in ventrolateral band; tentacle ossicles rods and mesh on primary rods; typical dense cover of globigerines.

Figures

Figure 3. a–b, M. atlanticus (NMV F101845, 210 mm long); a, ventral view; b, small epibiotes on body wall. c–e, M. constrictus sp. nov. (USNM 1022815, paratypes); c, dorsal view (51 mm long); d, ventral view (51 mm long); e, tube feet. f–g, M. crinitus sp. nov. (USNM 1023615, holotype, 96 mm long); f, ventral view; g, ventrolateral tube feet. h, M. depressus, pygal furrow, gelatinous body, lateral brim (NMV F101849). i–k, M. epibiotus sp. nov. (USNM 1008183, holotype, 110 mm long); i, ventral view, posterior taper; j, ventral mouth, epibiote concavities (arrows); k, ventral view, epibiote concavity (left arrow), few tube feet (central arrow). l, M. helios sp. nov., tentacle digits, tube feet (lower right) (USNM E31104, paratype). m–o, M. involutus (NMV F101850, 40 mm long); m, ventral view, serrated margin; n, dorsal anterior view, globigerines attached; o, posterior ventrolateral tube feet.

Figure 4. Tentacle ossicles (SEM). a–d, Meseres atlanticus, a–c (USNM E49466), d (USNM 1020067). e–h, M. crinitus sp. nov. (USNM E48662). i–l, M. depressus (USNM E53279). m–p, M. epibiotus sp. nov. (USNM 1008310, paratype). q–t, M. helios sp. nov., q–r (USNM E31104, paratype), s–t (USNM E31117, paratype). u–x, M. involutus (USNM E49256).