Thyone sp.

Thandar, Ahmed S., 2008, Additions to the holothuroid fauna of the southern African temperate faunistic provinces, with descriptions of new species, Zootaxa 1697 (1), pp. 1-57 : 12-13

Thyone sp. indet. 1

Figure 6A–G

Material examined

SAM-A27985, UCT Ecol. Surv., Van Veen, False Bay , St. FAL 434 , 34 o 15.2' S, 18 o 33.2' E, 16.v. 1961, 42 m, 1 spec.

Description

Specimen minute, obviously juvenile, length 3 mm, breadth in mid-body 1 mm. Form cylindrical, anterior end slightly turned up, mouth and anus terminal, anal papillae present. Colour uniformly white. Podia restricted to ambulacra, in two rows dorsally, none in dorsal interambulacra, also in two rows ventrally but few also scattered in interambulacra. Tentacles about 10, exact number and size could not be determined.

Calcareous ring not fully calcified ( Figure 6G ), radial and interradial plates of more or less same length, meeting proximally, compact, each radial plate with anterior depression for retractor muscle, interradial plates triangular; posterior processes of radial plates weakly developed, fragmentation not obvious. Polian vesicle and stone canal not detected. Gonad absent. Respiratory trees poorly branched, both reaching anterior third of body, each with less than ten sac-like branches.

Spicules of body wall comprise only tables ( Figure 6A ), disc 55-90 µm (mean 73 µm), smooth, oblong, perforated by four large central holes and about 3-15 peripheral holes of more or less similar size; spire of moderate height, up to 40 µm, of two pillars joined at apex and terminating in two points, each subdivided into two tooth-like projections, rarely more or less. Podia with tables and reduced end-plates; tables ( Figure 6B ) common, with curved disc, 62-87 µm (mean 74 µm), perforated by four large central holes and usually one at each end; spire of moderate height, 26-30 µm (mean 28 µm), of two pillars meeting at apex and terminating in two slightly diverging teeth. End-plates ( Figure 6C ) rounded with irregular margins, a few small central holes and several, usually larger marginal holes. Tentacles supported by plates of various form and size (45-70 µm) ( Figure 6D ), usually multilocular, with irregular margins and occasionally with medial knobs on surface. Introvert with huge multilocular plates ( Figure 6F ) with one or two knobs on the surface (?reduced spire) and tables ( Figure 6E ) with oblong disc perforated by four or more holes, margins irregular, spire terminating in one or more blunt teeth, or spire reduced.

Distibution False Bay , WCP, 42m.

Remarks

The single specimen is obviously a juvenile, judging from its size, distribution of podia, absence of the gonad and poor calcification of the calcareous ring. It seems unique amongst the southern African temperate dendrochirotids but the body wall tables come quite close to those of the tropical-subtropical T. comata Cherbonnier , differing in the form of the spires. Other differences are the form of the tentacle deposits, which in T. comata are rods and rosettes, as opposed to plates in the present specimen. The calcareous ring approaches that found in the Sclerodactylidae or the Sclerothyoninae , hence adult material is necessary. Since the southern African temperate, shallow-water dendrochirotids are highly endemic, it is unlikely that the specimen is referable to a species outside this region.

Figures

FIGURE 6A-G.. Thyone sp. indet. 1.. SAM-A27985. A. Tables from dorso-lateral body wall; B. tables from dorso-lateral podia; C. end-plate from dorso-lateral podium; D. plates from tentacles; E. small tables from introvert; F. large table from introvert; G. calcareous ring. H-J. Thyone sp. indet 2. SAM-A27986. H. Tables from body wall; I. rods from introvert; J. rods and rosettes from tentacles. A-F scale a; H-J scale b.