Holothuria (Cystipus) dura Cherbonnier and Feral 1981
Creators: name: Woo, Sau Pinn
name: Kajihara, Hiroshi
name: Iwasaki, Nozomu
name: Fujita, Toshihiko
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Aspidochirotida
Holothuriidae
Holothuria
Holothuria dura

description: Holothuria (Cystipus) dura Cherbonnier and Féral, 1981 (Figs 1–6)
Holothuria (Cystipus) dura Cherbonnier and Féral, 1981: 385–387, fig. 17A–M.
Holothuria dura: Améziane 2007: 342 [checklist].
Material examined. Two specimens: NSMT E-9839, southwest of Hahajima island, Ogasawara Islands, 26°33′30″N, 142°06′30″E, 126–261 m depth, 7 March 2015, ROV Hakuyo, collected by N. Iwasaki; NSMT E-9840, Okinoshima island, Sukumo, Kochi, 100–120 m depth.
Description. Body vermiform and straight. Approximate body length 14.0–20.9 cm in preserved state. Body surface of preserved specimens wrinkled and folded. Tentacles retracted; number undetermined. Oral opening ventral, surrounded by single ring of minute papillae. Body surface rough and gritty to touch. Two rows of dorsolateral conical papillae on each side; in living state, tapering with sharp tips and dark coloured with white ring at base; in preserved specimens, blunt in shape and brown in colour. Ventrolateral conical papillae 13 (NSMT E-9839) and 15 (NSMT E-9840) on left side, 15 (NSMT E-9839) and 14 (NSMT E-9840) on right side; some with bifurcate tips, especially those in middle part of body (Fig. 1C); bifurcation not obvious in preserved state (Fig. 2A, B). Ventral body flattened, white (Fig. 2B; NSMT E-9839) or light brown (NSMT E-9840) in colour. Number of tube feet undetermined due to contraction, not crowded and sparsely distributed along radii and interradii; light brown in colour, paler than dorsolateral conical papillae. Fifteen tentacular ampullae. Gonads single tuft. Respiratory tree single. Anus terminal.
Dorsal body wall containing table ossicles, modified table ossicles, and fenestrated ellipsoid ossicles (Fig. 3 A–C). Disc of tables 85–99 µm in diameter, very spinous with multiple perforations; four very low pillars with multiple and crowded short spines (Fig. 3C). Modified tables always smaller (diameter 15–20 µm) than tables. Knobs in modified table discs interconnected to spiny pillar forming fenestrated spheroids (Fig. 3B). Fenestrated ellipsoid (57–77 µm height) with smooth, knobbed surface, and irregular perforations (Fig. 3A). Ventral body wall with tables, modified tables, and fenestrated ellipsoids (Fig. 4 A–C). Disc of tables in ventral body smaller (diameter 73–87 µm) than those in dorsal body (Fig. 4C). Dorsal papillae containing modified tables, fenestrated ellipsoids, and rod ossicles (Fig. 5 A–C). Modified tables in papillae forming very knobby fenestrated spheroids (Fig. 5A). Rods in papillae with central perforations; the latter being 4–20 in number (Fig. 5C). Tentacles bearing rods with smooth surface; some spinelets present on rods, especially numerous at both ends (Fig. 6).
Distribution. Philippines (South China Sea), 100– 210 m (Cherbonnier and Féral 1981); New Caledonia (Améziane 2007); and Japan, 100–261 m (this study).
Remarks. Undoubtedly, our specimens can be identified as Holothuria (Cystipus) dura because they are morphologically consistent with the original description by Cherbonnier and Féral (1981). It is especially true in terms of the dorsolateral conical papillae, which are entirely darkcoloured with each base bordered by a white ring against the pale-coloured dorsal surface of the body; this character is unique among the 12 members in the subgenus Cystipus. One of the new findings in our in-situ observation is that the dorso-lateral conical papillae often taper to form an acutely pointed, often slightly curved, cone in the living state, with each tip directed upward (Fig. 1A, B), although they are mostly deformed in the preserved state (Fig. 2A).
Our SEM observation of the ossicles revealed that the tables found in the dorsal body and the ones in the papillae are highly modified, forming fenestrated spheroids. A similar ossicle was termed “pseudo-bouttons” (pseudo-buttons) by Cherbonnier and Féral (1981: 385); these were reported to vary in shape [from slightly nodular to elongate], in size, and in fenestration form (Cherbonnier and Féral 1981: fig. 17M), or to be several arrays of trabeculae (Cherbonnier and Féral 1981: fig. 17I). Moreover, table ossicles with 2–3 crossbeams (Cherbonnier and Féral 1981: fig. 17K) were not observed in our specimens, suggesting that these ossicles may vary in shape within the species.
With respect to the ventrolateral conical papillae, our study revealed that i) they vary intraspecifically in terms of the number [20 or so on each side in the type material vs. 13–15 papillae on each side in our material], and ii) at least some of the papillae are bifurcated. The latter condition may be a common feature among some member of the subgenus Cystipus that have prominent ventrolateral conical papillae, viz., H. (C.) jousseaumei Cherbonnier, 1954 and H. (C.) casoae Laguarda-Figueras and Solís-Marín, 2009, in addition to H. (C.) dura. Although bifurcation of the ventrolateral conical papillae was not mentioned in the original descriptions of these three species (Cherbonnier 1954; Cherbonnier and Féral 1981; Laguarda-Figueras and Solís-Marín 2009), it holds true at least in two of them, H. (C.) dura and H. (C.) casoae. As to the latter species, while we were not able to examine the actual specimens, the photograph illustrating the holotype specimen (Laguarda-Figueras and Solís-Marín 2009: fig. 1) clearly depicts the presence of bifurcation at the ventro-lateral conical papillae. Future studies should address commonality of bifurcation of the ventro-lateral conical papillae among the member of the subgenus Cystipus and other taxa, especially those occurring on sublittoral soft bottoms like H. (C.) dura.
Notes on locomotion. We infer that the ventrolateral conical papillae in Holothuria (Cystipus) dura are most likely used for locomotion in a similar manner to those holothurians occurring on deeper bottoms in the bathyal, abyssal, and hadal zones (200–6000 m depth) (Hansen 1972, 1975; Gebruk 1995). Contrary to deep-water species, shallowwater sea cucumbers in the intertidal to sublittoral zones (less than ∼ 200 m depth) generally utilize numerous tube feet to attach to the predominantly hard substratum, move, and undergo a wide range of activities (Hyman 1955; Flammang and Jangoux 1992). The enlarged ventrolateral conical papillae and the sparse density of ventral tube feet in H. (C.) dura indicate that the species has adopted the ‘walking’ strategy, in which they use ventrolateral conical papillae to move on the soft bottom (Hansen 1972). Furthermore, the bifurcation at the tips of the ventrolateral conical papillae could possibly be an adaptation to increase the surface of contact area against the substratum in order to maintain the efficiency of locomotion, at the same time compensating the decreased number of ventral tube feet. As the protraction and retraction of the ventrolateral conical papillae are maintained by hydrostatic pressure from the fluid contained in the dermal cavities (Hansen 1972; VandenSpiegel et al. 1995), bifurcation of the tips of the ventrolateral conical papillae in preserved specimens are obscured due to the loss of water content within the dermal cavities. However, judging from the in-situ photographs, bifurcation of papillae appears to be more obvious in the middle part of body rather than in the posterior and anterior ends (Fig. 1B). We speculate that this would be because papillae in the middle body require increased surface area against the bottom for powerful propulsion, whereas those in both ends of the body would be mainly used to control the direction of locomotion.
description: Published as part of Woo, Sau Pinn, Kajihara, Hiroshi, Iwasaki, Nozomu & Fujita, Toshihiko, 2017, First Record of Holothuria (Cystipus) dura (Echinodermata: Holothuroidea) from Japan, with Notes on Locomotion, pp. 45-52 in Species Diversity 22 (1) on pages 47-52, DOI: 10.12782/sd.22_45, http://zenodo.org/record/4585047