Molpadiodemas translucens, 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 : 163-164

Molpadiodemas translucens sp. nov.

Figures 2c , 5n, o , 8m –p , 12e, f

Material examined. Holotype. Weddell Sea, Antarctic Peninsula, 64°07'S, 40°48'W, 4465–4557 m, RV Eltanin, USARP Cr 12 stn 1018, 21 Mar 1964, USNM E48652 .

Paratypes. Type locality and date, USNM 1008072 (5) ; NMV F101863 (2).

Other material. South-east Pacific Basin, 4575–4813 m, E49487 (2).

Description. Up to 79 mm long; body wall thin, soft, translucent; no body attachments; body typically rounded in transverse section, not elongate, tapered anteriorly and posteriorly, lateroventral margin sometimes subacute or slightly bulbous; complete body cover of small, cylindrical, soft, scattered tube feet, erect or lying on body, typically 0.3 mm long, 0.1 mm diameter, rarely contiguous over most of body, slightly more concentrated ventrolaterally, most concentrated and frequently contiguous pygally, typically 0.6 mm long, 0.2 mm diameter; longitudinal muscles flat, slightly narrow; ossicles in tentacles and gonads; tentacle ossicles abundant, variable in form, thin to thick tapered smooth distally bluntly pointed rods sometimes with central rounded thickening, rods with intertwined branched ends creating small perforations, rods with fused side branches creating small lateral perforations, fused branches sometimes creating large perforated irregular mesh, ossicles up to at least 520 Μm long; gonad ossicles abundant, predominantly thin lace mesh with irregular large perforations, not developed on primary thick rod, some irregular finely spinous thin rods with irregular branching closing to create perforations, ossicles up to 320 Μm long.

Colour. Pale greyish brown, with traces of mauve colouration; tube feet off-white to semi-translucent.

Etymology. From the Latin lux (light) and trans (through), referring to the translucent body wall.

Distribution. South-east Pacific Basin, Weddell Sea, Antarctic Peninsula, 4465–4813 m.

Remarks. Amongst Molpadiodemas species, the distinguishing characters are: translucent body wall; lace mesh gonad ossicles.

Figures

Figure 2. Characters of Molpadiodemas. a, drawing of transverse section of mid-body, hair-like tube foot cover, flat broadly attached longitudinal muscles (as for M. villosus); b, flat longitudinal muscles, gonad (upper left), respiratory tree (upper right) (M. porphyrus sp. nov., NMV F101871, paratype, 90 mm long); c, complete cover of tube feet (M. translucens sp. nov., USNM 1008072, paratype); d, drawing of part of gonad, branched tubules from common origin; e, gonad, flat longitudinal muscles (arrows) (M. villosus, BMNH 86.10.2.155, paralectotype); f, branched gonad tubules (M. violaceus, BMNH 86.10.2.145).

Figure 5. a–d, Meseres morbillus sp. nov., a, lateral view (USNM 1008093, paratype, 91 mm long); b, tentacles, ventrolateral tube feet “spotting” (NMV F101865); c, tentacles, digits (USNM E49243); d, calcareous ring (radial plate right half) (USNM 1008093, paratype). e–g, M. neovillosus sp. nov.; e, dorsal view (USNM 1008458, paratype, 71 mm long); f, pygal end, tube feet (USNM 1008458); g, ventrolateral tube feet (BMNH 86.10.2.151, holotype). h–k, M. pediculus sp. nov.; h, dorsal view, elongate form (USNM 1008318, holotype, 56 mm long); i, ventrolateral tube feet (NMV F104796, paratype); j, tentacles (holotype); k, broadly attached, relatively narrow, slightly thickened, longitudinal muscles (arrows) (paratype). l–m, M. porphyrus sp. nov. (USNM E38795, holotype, 114 mm long); l, dorsal view, thick rounded brim; m, gonad. n–o, M. translucens sp. nov. (USNM E48652, holotype, 78 mm long); n, dorsal view, longitudinal muscles visible through translucent body wall (arrows); o, tentacles.

Figure 8. Tentacle ossicles (SEM). a–d, Meseres morbillus sp. nov. (USNM E49251). e–f, M. neovillosus sp. nov. (USNM 1008458, paratype). g–h, M. pediculus sp. nov. (USNM 1008318, holotype). i–l, M. porphyrus sp. nov. (USNM E38795, holotype). m–p, M. translucens sp. nov. (USNM E48652, holotype). q–t, M. villosus, q–r (USNM E48640), s–t (USNM E9929). u–x, M. violaceus, u–v (USNM 1022608), w–x (USNM E49366).

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).