Massinium magnum ( Ludwig, 1882 )

Samyn, Yves & Thandar, Ahmed S., 2010, Two new species in the phyllophorid genus Massinium (Echinodermata: Holothuroidea) with redescription of Massinium magnum, Zootaxa 2399, pp. 1-19 : 3-8

Massinium magnum ( Ludwig, 1882)

(figs 1A–E, 2A–H, 3A–N, 4A&B)

Thyonidium magnum Ludwig, 1882: 132 ; Lampert 1885: 170; Théel 1886: 146.

Phyllophorus magnus ; Ludwig 1889 –92: 347; Sluiter 1901: 112; pl. IV, fig. 5, pl. VII, fig. 1a–e; Domantay 1933: 38, pl. 2, fig. 11a–j; Domantay 1936: 399.

Neothyonidium magnum ; Heding & Panning 1954: 197, fig. 98; Clark & Rowe 1971: 182 (distribution);? George & George 1987: 246;? Rowe & Gates 1995: 312 (synonymy); Colin & Arneson 1995: 262, fig 1247; Gosliner et al. 1996: 283, fig. 1045; Erhardt & Moosleitner, 1997: 1151, 1152 (colour pictures); Forbes (ed.) et al.1999: 52; Massin 1999: 88, figs 72a–k, 73;? Lane et al. 2000: 491.

Neothyonidium magnum ; Cherbonnier 1980: 656, fig. 20A–Q; Féral & Cherbonnier 1986: 102, fig. 40T (non M. magnum ) (= M. albicans sp. nov.).

Thyone perissa H.L. Clark, 1938: 471 , fig. 43; Rowe & Gates 1995: 312 (synonymy).

Massinium magnum ; Samyn & Thandar 2003: 135, 141, 142 (passim).

Original name: Thyonidium magnum Ludwig, 1882 .

Name-bearing type: Holotype: NMNH-Leiden 1989 (calcareous ring with attached structures, introvert and tentacles only).

Type locality: Ambon, Moluccas, Indonesia.

Current status: Massinium magnum ( Ludwig, 1882) .

Material examined: NMNH-Leiden 1989 (holotype), Ambon (Molluccas, Indonesia), depth and collection data unknown, coll. E.W.A. Ludeking; ZMUA V. ECH.H.3431 (1 complete specimen), Siboga St. 213, Saleyer Reef ( Indonesia), up to 36 m deep, 26.ix.1899, coll. Siboga Expedition; ZMUA 3430 (3 specimens, one complete), Siboga St. 213, Saleyer Reef ( Indonesia), up to 36 m deep, 26.ix.1899, coll. Siboga Expedition; IG 28251/169 (calcareous ring and associated structures only), Kudingaieng Keke (SW Sulawesi, Indonesia), 14 m depth, 26.ix.1994, coll. C. Massin; NMNH ECH. 6090 (calcareous ring and associated structures only), Barang Lompo (SW Sulawesi, Indonesia), depth 3 m, 23.ix.1994, coll. C. Massin; IG 28455/ 51 (calcareous ring and associated structures only), Laing Island ( Papua New Guinea), depth 5 m, 16.x.1996, coll. C. Massin; IG 28455/54 (calcareous ring and associated structures only), Laing Island ( Papua New Guinea), depth 6 m, 17.x.1996, coll. C. Massin; AM J 13573 (one complete specimen and one calcareous ring and associated structures) (identified as N. perissum by F.W.E. Rowe), Heron Island (Queensland, Australia), depth ± 12 m, 12.xii.1979, coll. H. Silver; AM J 9490 (calcareous ring and associated structures only), Heron Island (Queensland, Australia), depth 10 m, 21.xi.1974, coll. N. Coleman.

Holotype description (after Ludwig 1882: 132, amended herein): Holotype consists of only the calcareous ring with its associated structures; length of complete fragment (excluding tentacles and Polian vesicles) 75 mm. Colour yellowish-brown, tube feet and tentacles darker brown. Mouth encircled by welldeveloped brownish-white peristomial membrane; tentacles 20, in two distinct circles, outer circle with five pairs of large (25–45 mm) tentacles, alternating with inner circle of five pairs of small (5–7 mm) tentacles; shaft large tentacles pale-brown with one dark banding proximally; tips large tentacles darker brown; shaft small tentacles uniform pale brown; tips small tentacles darker. Tube feet of introvert distributed in two radial rows over most of introvert length, decreasing in size proximally, where they also scatter over interradial areas. Calcareous ring (see Heding & Panning 1954: 197, fig. 98a) 70 mm long, tubular, spirally coiled, broken into a mosaic of small pieces camouflaged by a thick enveloping membrane; radial and interradial plates fused over about two thirds of length of calacreous ring; radial plates with deep anterior notch, posteriorly prolonged, bifurcating, processes fused with processes of neigbouring radial plates; interradial plates anteriorly pointed. Polian vesicles four, 150–180 mm long, tubular. Stone canal 20 mm long, ending in small truncated madreporite.

Ossicle assemblage. Introvert with tables and scarce rosettes (figs 1A, 2A). Tables with circular to ovoid to irregular disc with smooth rims and perforated by four large central holes and usually a single circle of alternating smaller holes, occasionally two. Table discs 60–80 Μm long and 55–60 Μm wide; spire low to moderate, of two pillars united by one to two cross-bars, ending in 4–6 tooth-like projections, sometimes subdivided. Rosettes 55–70 Μm long. Tube feet of introvert with numerous rosettes (figs 1B, 2B) and perforated irregular rods, sometimes forming plates (figs 1C, 2C). Rosettes 35–45 Μm long and 20–40 Μm wide, complex with distal endings swollen, not anastamosing. Rods 90–180 Μm long, with some large perforations and more smaller ones, ending with irregular branched projections. Peristome with numerous rosettes only (figs 1D, 2D), 30–65 Μm long, complex, roundish to elongate, endings distinctly swollen, never anastomosing. Shaft and tips of small and large tentacles with rosettes only, similar in size and shape to those of peristome (figs 2E–H). Longitudinal muscles of introvert devoid of ossicles. Gonoduct with rosettes, 25–30 Μm long, and lattice-like deposits, 80–100 Μm long (fig. 1E).

Remarks. Regrettably, the holotype lacks the main body of the animal and although its description is accurate, it is not accompanied by illustrations. Amongst the subsequent workers who examined the holotype only Heding & Panning (1954) provided a figure of its calcareous ring, but they too did not illustrate the ossicles, apart from two table deposits copied from Domantay (1933). Sluiter (1901) and Domantay (1933) accurately described complete specimens, but failed to illustrate the ossicle assemblage in detail, thus adding to the difficulty in correctly assigning specimens to M. magnum .

Therefore, to avoid confusion over the identity of M. magnum we have here re-described the type, supplementing it with a description of a complete specimen below.

Description of complete specimen [ZMUA V.ECH.H.3431]: Specimen entire, well-preserved. Body wall firm, but not thick (1–4 mm), slightly rough to the touch. Body form cylindrical, U-shaped, slightly contracted. Introvert well-extended, attached to main body by narrow, proximal end. Body length along ventral surface 118 mm, along dorsal surface 90 mm, height of mid-body 60 mm, length of introvert 85 mm, length of constricted proximal part 13 mm. Colouration of body and introvert uniform yellowish-white. Tube feet of body wall yellowish, numerous, retracted, scattered more or less evenly over dorsal and ventral radial and interradial areas, suckers small. Tube feet of introvert brownish, aligned in radial areas in two welldefined rows, except proximally where they also occur in interradial areas, absent in distal 30 mm. Tentacles 19, nine large, 10 small, arranged in two circles; large tentacles in outer circle, ± 60 mm long, in pairs in radial areas; small tentacles, in inner circle, ± 10 mm long, in pairs in interradial areas. Tentacles well branched, shaft yellowish-brown, some tentacles slightly banded; branches uniform dark brown. Anus retracted into body, presence or absence of anal teeth not determined. Calcareous ring 80 mm long, tubular, fragmented into a mosaic of small pieces obscured by thick membrane; radial and interradial plates fused over about seven eights of length of calcareous ring; radial plates posteriorly prolonged, bifurcating into processes which fuse with those of neighbouring radial plates. Polian vesicles four, white, 90–120 mm long. Stone canal single, slightly contorted, free, 26 mm long, terminating in small globular madreporite. Introvert retractor muscles thick and short, originating at anterior third of the body.

Ossicle assemblage. Body wall with rosettes, pseudobuttons and few tables, mostly reduced (figs 3A,B; 4A,B). Rosettes simple, slightly elongated, 25–40 Μm long; pseudobuttons of various shapes, with 2–10 small, randomly placed perforations; tables scarce, reduced to oval, smooth disc, generally with four large central holes and few smaller peripheral ones, occasionally with reduced spire. Tube feet of ventral and dorsal body wall with pseudobuttons, rosettes, elongated perforated plates surrounding endplate (fig 3C–F). Introvert with tables and occasionally rosettes (fig. 3G). Tables with oval, smooth disc, 45–80 Μm wide and 75–95 Μm long, perforated by four large central holes and usually one, occasionally two, circles of smaller peripheral holes, the larger of these alternating with the central holes, the other arranged more irregularly; spire consisting of two pillars, united by 1–2 cross-bars, terminating in some toothed projections. Tube feet of introvert with rosettes and irregular plates with branched ends (fig. 3H,J). Peristome with only complex rosettes, 50–75 Μm long (fig. 3K). Shaft and tips of both large and small tentacles sometimes with few rosettes. Longitudinal muscles of body wall with irregular perforated rods and pseudobuttons (fig. 3L). Longitudinal muscles of introvert devoid of ossicles. Cloacal retractor muscles with irregular deposits (fig 3M). Gonoduct with rosettes and lattice-like plates (fig. 3N).

Ecology: Massin (1999: 90) noted ‘…they live deeply buried in sand or coral rubble’ for material from Sulawesi and in 2005 (p. 69) ‘body always buried in sand, only tentacles and introvert visisble; tentacles coming out at sunset and at night’ for material from Papua New Guinea.

Remarks: The ossicle assemblage of the complete specimen here described (V.Ech.H. 3431) differs in some aspects from the holotype. For instance the tables of the introvert of the holotype have discs that are slightly smaller and less perforated than those of the complete specimen. However, comparison of the holotype and the other specimens we examined showed that this variation is to be considered intra- rather than interspecific. Nevertheless, we want to note that the second of Sluiter’s (1901) complete specimens (V.Ech.H. 3430, partim) differs slightly from his best preserved specimen described above (V.Ech.H. 3431) in presenting five minute calcareous teeth. However, as the ossicle assemblage of the introvert and tentacles of all of Sluiter’s specimens largely corresponds with that of the type, except for the abundance of ossicles in the tentacles and the presence or absence of rosettes in the longitudinal muscles of the introvert, we conclude that all these specimens are referable to M. magnum .

Finally, an important difference between all of Sluiter’s voucher material and the holotype, together with Massin’s voucher materials from Sulawesi (1999) and Papua New Guinea (2005), rests with the banding of the tentacles. Whereas the former shows a more uniform brownish colouration (see also Domantay 1933), the latter show clear banding at the base of the tentacles. There are also some differences in the ossicle assemblage of the muscles of the introvert between the type and Sluiter’s and Massin’s voucher materials: while the type, Massin’s Sulawesi material and two of Sluiter’s specimens did not present these ossicles, two of Sluiter’s Indonesia and both of Massin’s Papua New Guinea specimens did show these. More representative material from the whole distribution range of the species may eventually allow the separation of these slightly different forms which, for now, we retain under M. magnum .