Thyone okeni Bell, 1884

O’Loughlin, P. Mark, Barmos, Shari & VandenSpiegel, Didier, 2012, The phyllophorid sea cucumbers of southern Australia (Echinodermata: Holothuroidea: Dendrochirotida: Phyllophoridae), Memoirs of Museum Victoria 69, pp. 269-308 : 303

Thyone okeni Bell, 1884

Figures 17b , 22

Thyone okeni Bell, 1884: 149–150 , pl. 9D.—H. L. Clark, 1921: 167.—H. L. Clark, 1946: 402.— Rowe, 1982: 462 (non specimens from Port Phillip and Westernport in Victoria).— Rowe and Gates, 1995: 316 (non specimens from southern Australia).

Material examined. Australia, New South Wales, Port Jackson , AM J16905 (1) ; Vaucluse, Bottle and Glass Rock , under boulders, 21 Nov 1968, AM J7731 (1) ; 5 m, 29 Aug 1977, AM J10868 (2) ; mid-tide rock pools, 23 Oct 1968, NMV F174900 (1) ; off Nielsen Park , dredged, 21 Jan 1951, AM J16869 (1) ; Newcastle, Swansea Channel , 5 m, 21 May 1987, AM J20267 (1).

Diagnosis. Thyone species up to 75 mm long, up to 20 mm diameter (preserved, tentacle withdrawn; 85 mm long by Bell 1884); body cylindrical, oral and anal ends tapered, upturned; typically 10 tentacles, 8 large, 2 small ventral; body closely covered with tube feet, about 0.3–0.4 mm diameter, not more concentrated radially; no external evidence of anal scales or papillae; calcareous ring composite, tubular, no evidence of discrete plates for most of length, posterior composite tails not joined distally; radial plates with split anterior point, posterior end divided into two thin composite tails posterior to the end of the inter-radial plates; inter-radial plates tapered to anterior point, truncate posteriorly, about two thirds the length of radial plates; single long tubular polian vesicle; stone canal and madreporite lie anteriorly from attachment along calcareous ring; longitudinal muscles cylindrical, distinctly divided by deep groove mid-body.

Mid-body wall lacking ossicles; tube feet with endplates only, up to 240 µ m diameter lacking any support rods or tables or plates, endplate with irregular perforations, large marginally small centrally, slightly denticulate margin; peri-oral body wall with numerous tables, discs round to slightly oval, up to 192 µ m diameter/length, up to> 100 small perforations, spires thick short columnar mesh; tentacles branches with stout dumbbell-shaped ossicles, few to about 12 distal perforations, rods up to 320 µ m long, tentacle trunks lacking ossicles, no rosettes seen; introvert ossicles rosettes; anal ossicles rods as in tentacles, rosettes as in introvert, single and multi-layered scale fragments, tube foot endplate diameters up to 200 µ m.

Colour (preserved). Body brown to dark brown to grey-brown; tube feet off-white to grey to speckled to red; tentacle trunks off-white with brown patches, branches dark brown.

Type locality. New South Wales, Port Jackson .

Distribution. New South Wales, Port Jackson to Newcastle; 0– 5 m.

Remarks. The distribution extensions of Thyone okeni Bell, 1884 to Thursday Island off Cape York in northern Queensland (H. L. Clark 1921) and to Guam in the eastern Pacific ( Rowe and Doty 1977) are not confirmed. Thandar 1990 followed the comment by Rowe and Doty 1977 that Thyone okeni Bell was “probably distributed throughout the western Pacific area”, and without examining specimens was “inclined to think that T. venusta Selenka, 1868 and Thyone okeni were conspecific” and then formally relegated Thyone okeni Bell, 1884 to junior synonymy with Thyone venusta Selenka, 1868 (type locality the Red Sea). In the key in his paper Thandar (1990) described the body of Thyone venusta Selenka, 1868 as being violet at both ends, and the tube feet as lacking ossicles. Neither character is true of Thyone okeni Bell, 1884 . There are distinctive dumbbell-shaped endplate support rods in the tube feet of Thyone okeni Bell. We reject this synonymy on the basis of inadequate systematic evidence for these two species with widely separated type localities. Thyone okeni Bell, 1884 is distinguished from other southern Australia Thyone species in the key (above).

Figures

Figure 17. Photos of preserved specimens. a, holotype of Thyone flindersi O’Loughlin sp. nov. (NMV F151847) (insert: form of the calcareous ring plates); b, specimen of Thyone okeni Bell, 1884 (AM J10868); c, holotype of Thyone joshuai O’Loughlin sp. nov. (SAM K2566) (insert: form of the calcareous ring plates); d, holotype of Thyone kerkosa O’Loughlin sp. nov. (WAM Z31838); e, holotype of Thyone spenceri O’Loughlin sp. nov. (SAM K2562) (insert: form of the calcareous ring plates); f, holotype of Thyone tourvillei O’Loughlin sp. nov. (NMV F174902) (insert: form of the calcareous ring plates).

Figure 22. SEM images of ossicles from specimen of Thyone okeni Bell, 1884 (AM J7731). Peri-oral body wall rosette and tables with multibranched spires (top); dumbbell-shaped ossicles from tentacles (bottom).