Plesiocolochirus dispar ( Lampert, 1889 )

Thandar, Ahmed S., 2006, New species and new records of dendrochirotid and dactylochirotid holothuroids (Echinodermata: Holothuroidea) from off the east coast of South Africa, Zootaxa 1245, pp. 1-51 : 28-30

Plesiocolochirus dispar ( Lampert, 1889)

Figure 9

Colochirus dispar Lampert, 1889:820 , fig. 4; Ekman, 1918:32. pl. 3, fig. 25, pl. 4, fig. 26. Pentacta dispar Clark & Rowe, 1971:180 (dist.); Cherbonnier, 1988:164, fig. 68. Colochirus gravieri Vaney 1905:187 .

Pentacta gravieri Cherbonnier, 1955:162 , pl. 48, figs. k–s.

Pentacta trimorpha Clark, H.L. 1921:171 , pl. 37 (1–8).

Plesiocolochirus dispar Rowe (in Rowe & Gates 1995):278 (syn.)

Type

Syntypes perhaps in Stuttgart, Germany.

Type locality

Mermaid Strait, northwest Australia.

Previous southern African record

None.

Material examined

SAM ­ A23175, Coconut Bay, Mozambique, 17.v.1973, 1 spec.

Description

Form barrel­shaped, with dorsal surface arched and ventral flattened, sole­like, but sole not clearly defined; anterior end broad, posterior narrow and turned upwards. Length about 10 mm, diameter of anterior and posterior ends 5 mm and 2.5 mm respectively.

Colour uniformly white, including podia and tentacles. Podia restricted to ambulacra in double rows but most of those of mid­ventral ambulacrum retracted, except at anterior and extreme posterior ends; those of ventro­lateral ambulacra mostly well extended; dorsal podia indistinct because of scales which envelope most of dorsum. Ventral podia with well­developed suckers. Mouth star­shaped, boarded by five, distally calcified valves, especially the mid­ventral one which appears as a tooth­like structure. Tentacles 10, midventral two reduced. Anus terminal, surrounded by five teeth, each flanked by subterminal podia. Skin thin and rough to the touch.

Calcareous ring ( Figure 9 L) simple, well calcified, radial and interradial plates fused, radial plates with a bifid anterior prolongation for attachment of retractor muscle and a notched posterior surface; interradial plates shorter than radial plates, with a triangular anterior end and slightly indented posterior surface. Polian vesicle single, sac­like; stone canal short, free; madreporite ( Figure 9 K) spherical, grooved, lodged in the posterior notch of mid­dorsal interrradial plate. Respiratory trees delicate, extremely transparent but well branched, right tree reaches about one third the body length from anterior end, left one shorter. Gonad not observed. Longitudinal muscles unpaired, thin, well developed anteriorly, fused to body wall for most of their length. Retractor muscles arise as single strands from the anterior third of the longitudinal muscles.

Dorsal body wall invested in imbricating scales and, besides these, include deposits of four types: multi­layered buttons with large knobs; simple buttons with small knobs; usually complete baskets; and developing spicules of various shapes and sizes. Scales ( Figure 9 A) rather complex, oval, 105–875 µm long; small­knobbed buttons of various shapes and sizes ( Figure 9 B), 48–65 µm (mean 56 µm); large­knobbed buttons ( Figure 9 C), 58–71 µm (mean 63 µm), with four or more holes; baskets characteristic, flat ( Figure 9 E), 39–65 µm (mean 51 µm), with four large and four smaller alternating holes, surface spinose. Dorsal podia supported by perforated rods and plates ( Figure 9 F), 84–165 µm (mean 94 µm), some with marginal tuberosities ( Figure 9 G) and reduced endplates, 90–145 µm (mean 132 µm). Ventral podia with similar deposits but larger endplates, 170–240 µm (mean 202 µm) ( Figure 9 D). Tentacles supported by elongated, perforated rods, 42–258 µm (mean 107 µm), smaller in the branches ( Figure 9 H) and larger in the stalk ( Figure 9 J), as well as rosettes ( Figure 9 I), 16–32 µm (mean 24 µm).

Distribution

Tropical Indo­West Pacific, up to 20 m.

Remarks

The single specimen was at first thought to represent Psolidium ornatum ( E. Perrier, 1893) . However, Dr Rowe (pers. comm.) drew my attention to Plesiocolochirus dispar (Lampert) , a species which he thinks the specimen represents. I checked several descriptions of P. dispar and its synonyms and I concur with Dr Rowe without reservation. P. dispar has been recorded from the Red Sea and Somalia (see Clark & Rowe 1971) but this is its first record from southern Africa. However, the species was reported from Tuléar and Nosy Bay ( Madagascar) by Cherbonnier (1988) who also provides a detailed description of the species. The current specimen agrees well with that material.

Figures

FIGURE 9. Plesiocolochirus dispar (Lampert, 1889). SAM­A 23175. A. dorsal body wall scales; B. small­knobbed buttons; C. large­knobbed buttons; D. part of end­plate from ventral podia; E. closed baskets from dorsal body wall; F. smooth plates from dorsal podium; G. knobbed plates from dorsal podium; H. small rods from tentacles; I. rosettes from tentacles; J. large rods from tentacle stalk; K. madreporite; L. calcareous ring. B – H & J scale a; I scale b.