Actinocucumis typica Ludwig, 1875

P. Mark O’Loughlin, Melanie Mackenzie & Didier Vandenspiegel, 2014, New dendrochirotid sea cucumbers from northern Australia (Echinodermata: Holothuroidea: Dendrochirotida), Memoirs of Museum Victoria 72, pp. 5-23 : 19-20

Actinocucumis typica Ludwig, 1875

Actinocucumis typica Ludwig, 1875: 91 , fig. 24 a–d.— Lampert, 1885: 177.— Théel, 1886: 84, 125, pl. 12 figs 4, 5.— Ludwig, 1888: 817.— Erwe, 1913: 364–365, pl. 6 fig. 10a, b.

Actinocucumis typicus.— H. L. Clark, 1921: 170.— Clark, 1938: 479.— Clark, 1946: 403.— Heding and Panning, 1954: 72–74, figs 19, 20 (part).— A. M. Clark and Rowe, 1971: fig. 95 e, pl. 30 fig. 4 (part).— Liao and Clark, 1995: 481–482, fig. 290, pl. 23 fig. 10 (part).

Material examined. NE Australia, Queensland: Yeppoon, dredged off Middle Island , 23.13°S 150.74°E, 9–37m, B. J. Smith, 6 Sept 1967, NMV F204078 (1); Mackay harbour, 21.15°S 149.18°E, Ian Kirwan, 14 Jul 1982, NMV F206362 (1); near Cairns, Machans Beach, 16.85°S 145.73°E, on beach after cyclone, B. Collins, 25 Dec 1996, NMV F203016 (2); N Australia, Joseph Bonaparte Gulf, 11.55°S 129.82°E, RV Solander, 48 m, AIMS & GA, 26 Aug 2010, NMV F173265 (1) (GA lot SOL5117 lot 082BS040; UF tissue lot MOLAF1552 ) ; NW Australia, Dampier Archipelago , 1.3 km E of Eaglehawk I., FRV Flinders, DA 2/73/01, 20.67°S 116.46°E, coarse sand, 13 m, 24 Jul 1999, NMV F209501(1).

Diagnosis (sensu stricto). Dendrochirotid species, uniform brown colour (NMV F204078), or yellowish brown with some red patches and fine black flecking (NMV F173265), or pale brown to cream with fine brown flecking on body and larger brown patches on tube feet (NMV F206362); body pentagonal in section with raised radial ridges; five thick oral valves; about 20 dendritic tentacles, variable in arrangement and size, ventral pair smallest; tube feet confined to radii, small papillae and tube feet also on radii and encroaching inter-radially; tube feet in 4–6 rows (80 mm long specimen, Ludwig 1875), or in paired rows (smaller 35–44 mm long specimens, this work); calcareous ring not composite, radial plates with vertical sides, radial and inter-radial plates lacking posterior prolongations.

Body wall ossicles abundant, crowded, small plates and ellipsoids, and rare, thick large plates; bi-perforate plates (figure-8 form, “acorn” plates in Ludwig 1875 and Clark 1938, 1946) predominate, up to about 40–50 µ m long with one central and 5 marginal knobs, the apical knob typically projecting; bi-perforate plates inter-grade with abundant but less numerous irregularly ovoid fenestrated ellipsoids, up to about 40–55 µ m long; large plates thick, irregular in outline, perforation sizes irregular, plates frequently more than 150 µ m long. Tube feet with endplates and support tables; large endplate diameters about 240 µ m, small endplate diameters about 120 µ m; table discs elongate, up to 160 µ m long, narrow, widened centrally and distally, spires with 4-pillar base, pillars frequently joined to form an arch, arches frequently with single, long, thick, pointed, apical spine. Introvert with abundant tables, spires with four-pillar base and pillars fused with distal narrow arch or long spine or 2 short blunt spines. Papillae with body wall ossicles, rare tables, and lacking endplates. Lacking anal scales.

Remarks. Because uncertainty remains about the assignment of species to this genus we provide a sensu stricto diagnosis of Actinocucumis typica , based on the morphological characters of the type species. We examined six northern Australian specimens of Actinocucumis (listed above). We confidently judge that four of these specimens are Actinocucumis typica as all of their morphological characters closely fit the original description and illustrations by Ludwig (1875). These characters are detailed in the generic diagnosis above. With less confidence we judge that the two beach-washed specimens are also A. typica (NMV F203016).

The ossicles of specimens from the Philippines that are illustrated by Reyes-Leonardo et al. (1985) appear to us to be close to those illustrated for Actinocucumis longipedes , although the description refers to the presence of fenestrated ellipsoids and irregular tables with pointed spires. The descriptive reference to “wart-like” podia scattered all over the body” is not characteristic of A. typica .