Thyone

Thandar, Ahmed S., 2009, New species and a new record of sea cucumbers from deep waters of the South African temperate region (Echinodermata: Holothuroidea), Zootaxa 2013, pp. 30-42 : 35

Thyone sp.

Figure 4

Material examined. SAM-A28045, ‘Africana 232’, Trawl 39, St.27362, south coast of South Africa (34° 24’S, 23° 08’E), 102 m, 12.iv.2007, Louise Lange, 1 spec. (red).

Description. Specimen received dried-out but prolonged soaking in alcohol softened body wall to some extent. Form cylindrical, gherkin-like, posterior end narrowed and constricted, perhaps an artefact of preservation. Length 40 mm, diameter in mid-body 8 mm, posterior end diameter 2 mm. Live colouration recorded as red but preserved specimen a dull-greyish brown, darker anteriorly and posteriorly. Mouth anterior, tentacle number impossible to determine due to previous desiccation; anus terminal, anal teeth conspicuous. Podia minute, scattered, ventrally with some indication of their arrangement in rows, suckers reduced. Body wall thin (<1 mm), leathery, slightly rough to the touch.

Calcareous ring ( Figure 4 A) complex, tubular, tube about 7 mm long, fragmented into a mosaic. Anterior tips of radial plates bifid, tips wing-like; interradial plates triangular, each with sharp anterior projection; radial plates prolonged posteriorly before bifurcating into paired processes. Processes up to 10 mm long, delicate, intertwined but distally well separated, each process broken into a series of delicate fragments. Polian vesicle(s) not detected. Stone canal short, thin, membranous. Madreporite white, bean-shaped. Gonad (testis) mature, tubules long, coiled, unbranched, situated in middle of body. Respiratory trees poorly branched, left one more so, restricted to posterior half of body; right tree longer, both trees open independently into cloaca. Retractor muscles arise from unpaired longitudinal bands to insert on anterior projections of radial plates of calcareous ring.

Except for reduced and often incomplete end-plates in the podia ( Figure 4 B, C), no ossicles detected in body wall (including anal region), podia and introvert. End-plates up to 80 µm. Tentacles with straight or slightly curved rods, up to 200 µm, usually perforated in the middle and at ends ( Figure 4 D).

Remarks. Due to the singularity of the specimen, its previous drying-up and the absence of body wall, podial and introvert ossicles, it is not possible to name it with any degree of certainty. It does not appear to be identical to any Thyone species currently known from the southern African region. Because of the peculiarities of its calcareous ring it appears highly likely that more and better preserved specimen will lead to the description of a new species. As the South African temperate dendrochirotids are highly endemic it does not seem likely that the single specimen is referable to a species outside the southern African region.

Figures

FIGURE 4. Thyone sp. A. Dorsal part of calcareous ring; B. reduced end-plate from a dorsal podium; C. complete endplate from ventral podium; D. rods from tentacle. A scale a; rest scale b.