Molpadia sp.

THANDAR, AHMED S., 2007, Additions to the aspidochirotid, molpadid and apodid holothuroids (Echinodermata: Holothuroidea) from the east coast of southern Africa, with descriptions of new species, Zootaxa 1414 (1), pp. 1-62 : 52

Molpadia sp. indet.

Figure 24

Material examined

SAM-A27949 , off Tongaat Bluff , KZN, 29° 44.4' S, 31° 25.4' E , NMDP, St. ZV 7, 20.vi. 1989, 240 m, 1 spec.

Description

Specimen of medium size, length (including tail) 25 mm, breadth 15 mm, tail partially retracted. Colour, in alcohol, greyish-brown, darker ventrally, with rust-coloured tinges indicating phosphatic deposits, common at both ends, tail whitish. Tentacles 15, small (ca. 1 mm), whitish, each with a pair of digits and a single unpaired terminal digit. Anus encircled by minute teeth (only observed during spicule preparation), each a delicate sterome ( Figure 24H ) with large hole close to proximal end. Skin thin, rough, translucent.

Calcareous ring ( Figure 24G ) sculptured, plates fused, radials with a terminally bifid posterior projection and an anterior notch; interradials with triangular anterior projection of same length as that of radial plate. Tentacle ampullae short, (ca. 2 mm); Polian vesicle single, elongated; stone canal not detected. Respiratory trees delicate, arising independently; right longer, with sac-like branches, better developed proximally; left tree restricted to posterior half of body. Gonad immature, as two tufts of anteriorly attached dichotomously branched tubules.Longitudinal muscles paired, members of each pair uniting before insertion. Ciliary urns not detected.

Spicules of body wall comprising tables of two sizes, with well-developed spires, projecting well out from surface. Large tables ( Figure 24A, D ) with 238–529 µm disc (mean 425 µm), perforated by about 4–7 holes and with 4–6 long, blunt, undivided arms; spire high ( Figure 24A, B ), 114–267 µm (mean 222 µm), of three fused pillars terminating bluntly or in 2–3 teeth, with some evidence of former cross-bridges; smaller tables ( Figure 24C ) with usually trilobed, tri-perforate disc, 171–238 µm (mean 200 µm), if disc multi-lobed then with one or more marginal projections and up to six holes; trilobed tables are of the T. triforia type (see above) with tall (124–171 µm) spires and some evidence of several cross-bridges. Tail tables of typical Molpadia type ( Figure 24E ), with fusiform disc, 88–196 µm (mean 152 µm), perforated by up to four small central holes; spire low, 13–27 µm (mean 23 µm), of usually fused pillars, occasionally a single cross-bar, and terminating in about four teeth. Some distorted or developing tables also commonly present in tail ( Figure 24F ) with disc 46–81 µm (mean 65 µm), spire 13–23 µm. Tentacle deposits absent.

Remarks

The specimen at hand is so similar in external appearance to Molpadia triforia that I was at first inclined to consider it conspecific with this species. However, only the smaller tables with a tri-lobed disc are reminiscent of T. triforia , the large ones with multi-armed discs and more holes are so different that it is possible that the present specimen represents a new species. I have refrained from describing it as such as species within the genus are notorious in transforming their spicules with age so much so that many workers have cautioned against erecting or naming species on scant material until a complete series is available. The specimen also comes close to T. parvulum Cherbonnier & Féral, 1981 from the Philippines at 510 m, but its radial plate projections are only terminally bifid and the large tables quite distinctive with straight and not inwardly curved arms.

Figures

FIGURE 24. Molpadia sp. indet. SAM–A27949. A. large tables from body wall; B. spire from a large body wall table; C. small tables from body wall; D. developing body wall tables; E. tables from tail; F. distorted tables from tail; G. calcareous ring; H. anal tooth. (A–D scale a; E & F scale b)