Selenkiella paradoxa Cherbonnier, 1970

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 : 14-16

Selenkiella paradoxa Cherbonnier, 1970

Figure 4

Selenkiella paradoxa Cherbonnier, 1970: 291 –293, fig. 6 (A–P); Day, 1974: 94; Cherbonnier, 1988: 234 –235, fig. 103; Thandar, 1990:219 –221, fig. 9 a–f. Type

MNHNP.

Type locality

Morrumbene, Mozambique, 35 cm.

Previous South African record

None

Material examined

SAM­A27900, SE of Durban Bluff, 29 59.9’ S, 31 03.8’ E, ‘Meiring Naude’, St. XX 146, R. Kilburn, 13 vi 1989, 60 m, 1 spec. (female); SAM­A27901, off Mngeni River Mouth, Durban, 29 49.8’ S, 31 12.2’ E, ‘Meiring Naude’, St.XX 149, R. Kilburn, 13 vi 1989, 95 m, 1 spec.

Description

Larger of the two specimens barrel­shaped, slightly bloated ventrally; length approximately 41 mm, width of mid­body 10 mm, height about 14 mm. Colour, in alcohol, a variegated greyish­brown, suckers white; skin wrinkled. Mouth anterior, anus terminal, the latter flanked by minute calcareous teeth, not easily visible. Podia scattered, not confined to ambulacra, more numerous ventrally, suckers well developed. Tentacles 25, retracted, arranged in three rings of 10+10+5, however, first and second rings not clearly defined. All tentacles well branched, brownish in colour with lighter stalks. Body wall soft, smooth to the touch.

Calcareous ring complex ( Figure 4 U), tubular, with unbroken radial plates, slightly higher than interradial plates and carrying short, thick, paired, inwardly curled processes fragmented into few segments, several anterior notches and a depression for insertion of retractor muscle; interradial plates roughly triangular, not notched, but anteriorly pointed, and broken into two pieces; calcareous ring, including processes, about 7 mm long. Polian vesicle single, large, sac­like. Stone canal short, white, embedded in dorsal mesentery; madreporic body ( Figure 4 T) somewhat oval, well calcified, also lodged in mesentery. Respiratory trees well branched, right one slightly longer than left, both reaching anterior third of body, uniting before opening into cloaca. Cloaca narrow, elongate, suspensors well developed. Gonad (ovary) in two tufts of short, unbranched tubules full of eggs, left tuft better developed than right. Longitudinal muscles thick, unbranched. Retractor muscles well developed, originating from anterior third of longitudinal bands, slightly more anteriorly in the two dorsal ambulacra.

Spicules of the dorsal, lateral and ventral body wall identical, comprising minute rods (29–76 µm, mean 54 µm), pseudobuttons, tables with reduced spires (47–69 µm, mean 63 µm) and rosettes (36–61 µm, mean 45 µm). Rods ( Figure 4 E.) numerous, smooth, with or without perforations, either representing complete spicules or developmental stages of pseudobuttons and tables. Pseudobuttons ( Figure 4 A, B) numerous, with 1–6 holes. Table discs ( Figure 4 C) subcircular to oval, with usually a smooth rim, two or more holes and commonly a pair of nodules indicating reduced spires. Rosettes ( Figure 4 D) equally developed dorsally and ventrally, originating from branched, anastomosing rods, which may or may not leave perforations — larger rosettes usually with perforations, smaller ones without. Anal region with better­developed tables ( Figure 4 P, Q), with usually an oval to round disc (50–98 µm, mean 76 µm) with an undulating rim, four central holes and a short (14–25 µm, mean 21 µm) spire of four pillars, ending in usually a quadrangular crown bearing a few blunt teeth. Podial deposits include rods ( Figure 4 H, K) and pseudobuttons, identical to those of body wall but slightly larger (31–164 µm, mean 79 µm), other more specialized plate­like rods (82–200 µm, mean 130 µm) ( Figure 4 I, J), better developed ventrally, with a series of perforations along their length or with one or two perforations at ends, as well as typical, elongated (112–216 µm, mean 156 µm), multilocular plates ( Figure 4 F, G). Endplates up to 407 µm in diameter, with an irregular margin and numerous small to large holes scattered without any regular order ( Figure 4 S). Tentacle deposits only comprise straight or curved slender rods ( Figure 4 N) (40–168 µm, mean 85 µm) with slightly expanded, digitated ends carrying one or two perforations, and rosettes ( Figure 4 M) similar to those of body wall but slightly larger (26–93 µm, mean 51 µm). Introvert with only rosettes developed as minute (44–76 µm, mean 55 µm) branched rods ( Figure 4 L). Cloacal suspensors with branched rods (35–82 µm, mean 52 µm) developed as ‘pseudobuttons’ or rosette­like spicules ( Figure 4 R). Gonad with slender rods bearing one or more processes ( Figure 4 O), sometimes developed as apophyses, resembling those of the spicules of some elasipodids, notably Elpidia species. Retractor muscles without spicules.

Habitat

Fine sand, mud and seaweeds.

Remarks

This species was based only on the holotype collected from Morrumbene ( Mozambique) at 35 cm ( Cherbonnier 1970) but Cherbonnier (1988) states that the holotype came from a depth of 35 m. The latter depth record hence appears to be a lapsus calami as is also Thandar’ s (1990) depth record of 3–5 m for the holotype. The species is also reported to occur at Inhaca Island, off Maputo ( Mozambique), but this could not be confirmed. Hence the second definite record of the species is that of Cherbonnier (1988), based on seven specimens collected from Tuléar ( Madagascar). The present specimens from around Durban thus extend the known distribution of the species, and also double its recorded size. Both Cherbonnier (1970) and Thandar (1990) compare this wellcharacterised species with its two congenors, S. siamense Heding and Panning 1954 , the type species, and S. malayense Heding and Panning 1954 . Cherbonnier (1970, 1988) states that the tentacles are in two circles of 15 large tentacles on the outside and 10 small tentacles on the inside. However, in the large specimen, described above, there are clearly five very small tentacles on the inside and 20 large tentacles, apparently arranged in two rings, on the outside. This difference may not be very significant as the arrangement cannot be clearly discerned if the tentacles are retracted. Also insignificant is the fragmentation of the interradial plates. These differences and a few others concerning the spicules may be geographic variations in this species which is well characterised by its pseudobuttons and rosettes in the body wall, and elongated multilocular plates in the podia.

Figures

FIGURE 4. Selenkiella paradoxa Cherbonnier, 1970. SAM­A 27900. A. pseudobuttons from lateral body wall; B. side view of pseudobuttons from lateral body wall; C. reduced tables from body wall; D. three types from rosettes from body wall; E. rods from body wall; F. plates from ventral podia; G. plates from dorsal podia; H. rods from dorsal podia; I. plate­like rods from dorsal podia; J. rods from ventral podia; K. minute rods from ventral podia; L. rosettes from introvert; M. mulberry­like rosettes from tentacles; N. rods from tentacles; O. rods from gonad; P. tables from anal region; Q. side view of tables from anal tables; R. rosette­like plates and rods from cloacal muscles; S. part of end­plate; T. madreporite; U. calcareous ring. A­R scale a.