Deima oloughlini Mackenzie & Davey
Authors: Liao, Xiaomei, Li, Jun, Xu, Ningxia, Li, Xinlong, Ge, Meiling, Zhang, Tonghui, Li, Min, Zhang, Xuelei, Xu, Qinzeng
Type: Taxonomic treatment
Published: 2026-07-29
Keywords: Biodiversity, Taxonomy, Animalia, Echinodermata, Holothuroidea, Synallactida, Deimatidae, Deima, Deima oloughlini

<p><i>Deima oloughlini</i> Mackenzie & Davey in Mackenzie et al. 2024</p><p>Figs 2, 3, 4</p><p><i>Deima oloughlini</i> Mackenzie & Davey in Mackenzie et al. 2024: 264–266, fig. 37.</p><p><b>Material examined.</b></p><p>Two specimens. FIO-IND 72 - JLBEN 208 D 1 (JL 208 D 1), collected from Ninety East Ridge, Indian Ocean, JL 208 (3°48'59.10"N, 90°06'07.50"E), depth 2557 m, 9 May 2022, preserved at -80°C. FIO-IND 72 - JLBEN 208 D 2 (JL 208 D 2), collected from Ninety East Ridge, Indian Ocean, dive JL 208 (3°48'13.20"N, 90°05'53.93"E), depth 2447 m, [9 May 2022], preserved at -80°C.</p><p><b>Description.</b></p><p><i>External morphology</i>. Body cylindrical, slightly flattened ventrally, skin smooth, color <i>in vivo</i> pink to reddish (Fig. 2 C, E). The body width about 5–7.5 cm, and length approximately 13–17 cm (Fig. 2 A, B, D). The base diameter of the dorsal papillae approximately 0.7–0.9 cm, with a length of 6–11 cm (Fig. 2 A). Dorsal papillae flesh-pink, tips darker. Tube feet overall darker than papillae, tips red-black. Tube feet basal diameter approximately 700–1100 µm, length about 1600–3500 µm (Fig. 2 A, B, D). Ventral mouth encircled by a raised, annular ridge, with retracted tentacles visible within. Dorsal papillae arranged in a bilateral symmetrical pattern. 6 pairs of slender medial papillae and 6 pairs of longer lateral papillae, all arranged symmetrically (Fig. 2 A, B, D). Ventrolateral tube feet in approximately 11 on both sides of the abdomen. Tentacles retracted, number undetermined (Fig. 2 A, B, D).</p><p><i>Ossicle morphology</i>. Ossicles extracted from five body parts: dorsal body wall, ventral body wall, papillae, tube feet, and tentacles. The dorsal body wall deposits comprised three types of ossicles: perforated plates (Fig. 3 A: a – e, diameter about 500–1900 µm); rods (Fig. 3 A: g – o, 120–260 µm in length); and bifurcated crosses (Fig. 3 A: f, 170–180 µm in length). The ventral body wall contained two types of ossicles (Fig. 3 B: a – i). The perforated plates on the ventral side are smaller than those on the dorsal side, but some are also large, for example, one measuring ~ 1050 µm in diameter (Fig. 3 B: b). Papillae contain perforated plates (Fig. 3 C: a – d, diameter 1200–1800 µm), edges open or closed; bifurcated crosses (Fig. 3 C: f, 200–280 µm in length) are also in papillae, similar to those in the dorsal body wall (Fig. 3 A: f). Tube feet with several kinds of ossicles (Fig. 3 D: a – k): perforated plates with central spikes (Fig. 3 D: a, b, diameter 720–760 µm), bifurcated crosses (Fig. 3 D: c, 210–220 µm in length), robust rods with spines (Fig. 3 D: d, e, 230–300 µm in length), flattened rods with serrated edges (Fig. 3 D: f, 190–200 µm in length, 15–35 µm in width), and rods bifurcated at both ends (Fig. 3 D: g, h, 230–270 µm in length), along with three distinctively shaped sclerites (Fig. 3 D: i – k). The tentacle deposits contained various rod-like structures (Fig. 3 E: a – c, g – i, 230–430 µm in length) and two odd forms (Fig. 3 E: e, f 220–240 µm in length), one of which was an irregular, branched rod-like ossicle (Fig. 3 E: e). Smaller perforated plates with central spines (Fig. 3 E: d, diameter 270–280 µm) are also present in the tentacles, appearing more compact compared to those found in other tissue sections.</p><p><b>Variability.</b></p><p>FIO-IND 72 - JLBEN 208 D 2 (JL 208 D 2) specimen body cylindrical; color <i>in vivo</i> pink. The JL 208 D 2 specimen measured approximately 13 cm in length and 5 cm in width when collected, size smaller than JL 208 D 1 (FIO-IND 72 - JLBEN 208 D 1). Ossicles extracted from five body parts of the JL 208 D 2 (Fig. 4). The dominant ossicles are perforated plates and various rods. However, some perforated plates with a distinctly three-dimensional architecture (Fig. 4 A: a, Fig. 4 C: a, b, diameter 540–840 µm), more reminiscent of table-shaped ossicles; several rods here more strongly curved and bearing markedly longer branches. Dorsal and ventral body wall with some very thin rods (Fig. 4 A: l – n, Fig. 4 B: h, k, o); tube feet and tentacles rods stout and ramified (Fig. 4 D: b – f, k, Fig. 4 E: e, f).</p><p><b>Distribution.</b></p><p>Indian Ocean, Australian IOT, Cocos (Keeling) Islands Territory, Cocos (Keeling) Stn and Rudist Seamount Stn, at depths of 1175–1896 m; the Ninety East Ridge, Indian Ocean, at depths of 2447–2557 m.</p><p><b>Remarks.</b></p><p>The examined specimens (FIO-IND 72 - JLBEN 208 D 1 and FIO-IND 72 - JLBEN 208 D 2) are assigned to <i>Deima oloughlini</i> Mackenzie & Davey, 2024 based on external morphology and ossicle characters. Both specimens conform to the diagnostic range of <i>D. oloughlini</i>, including 6 pairs of dorsal papillae and 4–6 pairs of ventrolateral papillae. Both JL 208 D 1 and JL 208 D 2 possess 6 pairs of dorsal papillae and 6 pairs of ventrolateral papillae. Tube feet are arranged in approximately 11 pairs, consistent with intraspecific variation reported for <i>D. oloughlini</i>. In the dorsal and ventral body wall, the ossicles are mainly irregular perforated plates, mostly single-layered and occasionally showing rudimentary secondary meshwork or branching; this condition agrees with the original description of <i>D. oloughlini</i> by Mackenzie et al. (2024).</p><p>Historically, the genus <i>Deima</i> has included six recognized species: <i>D. atlanticum</i> Hérouard, 1898, <i>D. blakei</i> Théel, 1886, <i>D. fastosum</i> Théel, 1879, <i>D. mosaicum</i> Ohshima, 1915, <i>D. validum</i> Théel, 1879; and <i>D. pacificum</i> Ludwig, 1894. The first five were treated as subspecies of <i>D. validum validum</i>, while <i>D. pacificum</i> was regarded as <i>D. validum pacificum</i>. In the present material, ossicles were examined separately from the dorsal body wall, ventral body wall, papillae, tube feet, and tentacles. In the dorsal and ventral body wall, the ossicles are mainly irregular perforated plates, mostly single-layered and occasionally showing rudimentary secondary meshwork or branching, which agrees with the original description of <i>D. oloughlini</i> by Mackenzie et al. (2024). Rod-like ossicles were also observed in several body regions, especially in the tube feet and tentacles. Because ossicle descriptions in previous <i>Deima</i> studies have often focused mainly on body-wall plates, these region-specific observations provide supplementary comparative information for <i>D. oloughlini</i> and other <i>Deima</i> taxa, but are not treated here as evidence for species-level separation.</p><p>Previous accounts of the genus have focused almost exclusively on perforated plates, with rods scarcely mentioned; in contrast, our specimens possess a striking variety of rod-shaped ossicles in the dorsal and ventral body walls, tube feet, and tentacles. Overall, the combination of region-specific ossicle composition and appendicular rod polymorphism is consistent with the assignment of the present material to <i>D. oloughlini</i>. The occurrence of this species at the Ninety East Ridge represents a new record from the northern Indian Ocean.</p>