Thyone hirta Cherbonnier, 1970

Thandar, Ahmed S., 2018, On some miscellaneous sea cucumbers (Echinodermata: Holothuroidea) in the collections of the South African Museum with three new species, Zootaxa 4532 (1), pp. 57-85 : 68-69

Thyone hirta Cherbonnier, 1970

( Figure 9 )

Thyone hirta Cherbonnier, 1970: 288 , fig. 4 N–S, fig. 5 A, B; Thandar, 1990:214; 2008: 6, fig. 2 A–F.

Thyone sp. indet. 1 Thandar, 2008:12, fig. 6 A–G.

Material examined. SAMC-A 090916 , SM 185, off Port Alfred , 33°39.03’ S, 27°11.06’ E, heavy dredge, 90 m, 31.V.1978, 1 spec .

Diagnosis (see Cherbonnier 1970; Thandar 1990).

Description. Specimen minute, brittle, perhaps due to previous drying-up. Form sub-cylindrical, dorsal surface arched, ventral surface flattened and concave ( Figure 8A ). Colour pinkish-white to off-white. Length about 5 mm, breadth in mid-body about 2 mm. Tentacles 10, retracted, bushy, in 8+2 arrangement, 8 large ones of various sizes. Anterior end narrower than posterior. Anus terminal, anal teeth non-evident. Tube feet scattered, dorsally mostly retracted with some serial arrangement, more numerous ventrally, suckers reduced, of more or less same diameter as tube feet. Calcareous ring poorly calcified ( Figure 8E ), radial and interradial plates loosely united at base, the former deeply incised, processes short, weakly developed. Gonadal tubules immature. Body wall ossicles comprise tables (45–70 µm) with a circular/oblong disc, perforated by numerous small holes ( Figure 8B ); spire of moderate height (20–30 µm), comprising two pillars with a single low cross-bar and terminating in two diverging processes, with each bearing one or more teeth. Some multilocular discs without spire, also present. Tube feet ossicles comprise tables (55–95 µm) with a curved disc, spire (15–30 µm), also two- pillared, ending in two teeth of which one or both may be subdivided into minor denticulations ( Figure 8C ). Some tube feet tables with less curved discs and no spire. End-plates well developed, circular, with small medial holes, and large peripheral holes ( Figure 8D ). Tentacle ossicles include small plates of various forms. Introvert ossicles as tables only, much like those of body wall; some tables with large discs also present, but rare; some appearing as plates with medial knobs which perhaps represent reduced spires of degenerating tables.

Distribution. False Bay and Port Alfred, Eastern Cape Province, 48– 90 m.

Remarks. The current specimen taken from off Port Alfred in the Eastern Cape Province at 90 m corresponds very well with Thyone sp. indet.1 described by Thandar (2008) from False Bay in the Western Cape Province at 42 m, judging from its calcareous ring and deposits. However, Thandar (2008) compared his indeterminate form with T. comata Cherbonnier, 1970 , a tropical sub-tropical species, and not with T. hirta which he also described in the same paper. This error of judgement is regretted since it now appears that his indeterminate form, as well as the current specimen, are both referable to Thyone hirta except for the form of the calcareous ring which perhaps influenced Thandar’s original determination. Since both Thandar’s Thyone sp. indet. 1 and the current specimen are juvenile not much emphasis can be placed on the form of the calcareous ring which is reputed to change drastically with growth in most Thyone species. However, the body wall, tube-feet, tentacles and introvert ossicles are identical to those of T. hirta illustrated both by Cherbonnier (1970) and Thandar (2008).

Figures

FIGURE 8. Stereoderma mohammedi n.sp. SAMC-A090915. A. Specimen (entire); B. Body wall ossicles with nodules; C. Smooth body wall ossicles; D. Polygonal body wall ossicles with nodules; E. Spinous tube feet rods; F. Part of calcareous ring (dorsal).

FIGURE 9. Thyone hirta Cherbonnier, 1970. SAMC-A090916. A. Specimen (entire) juvenile; B. Tables from body wall; C. Tables from tube feet; D. Tube feet end-plate; E. Part of calcareous ring (dorsal view).