Hemiocnus tegulatus Yamana & Kohtsuka 2018, comb. nov.
Creators: name: Yamana, Yusuke
name: Kohtsuka, Hisanori
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Dendrochirotida
Cucumariidae
Hemiocnus
Hemiocnus tegulatus

description: Hemiocnus tegulatus (Augustin, 1908) comb. nov.
[New Japanese name: Kawara-kinko]
(Figs 1D, 2D, 6A–I)
Cucumaria tegulata Augustin, 1908: 24 –25, Textfig. 16, 17, Tafel II, fig. 1.
Cucumaria capensis: Ohshima 1915: 258. Pseudocnus sp.?: Okanishi et al. 2016: 22, fig. 8 I. non: Cucumaria capensis Théel, 1886: 62 –64, Pl. V, fig. 2. with which this species was previously synonymized by Ohshima
1915 = Ocnus capensis (Théel, 1886): according to Thandar 1991: 119–120, Figures 4, 5 and 14b. non: Cucumaria capensis var. parva Mitsukuri, 1912: 233 –235, Textfig. 45, Pl. VIII, fig. 74. = Plesiocolochirus inornatus
(Marenzeller, 1881). non: Psolidocnus tegulata (Augustin, 1908): Kuramochi & Kuramochi 2016: 17–18, fig. 2, 3. = Plesiocolochirus inornatus
(Marenzeller, 1881).
Material examined. 1 specimen, WMNH-INV-2015-378 (St. 2, 25 June 2015, length 9 mm, width 3 mm); 1 specimen, WMNH-INV-2015-379 (St. 3, 24 June 2015, length 10 mm, width 5 mm).
Description. Body barrel-shaped, straight or slightly curved (Fig. 1D); body wall hardened. Color of live specimens white, (not changing in alcohol); in addition, live specimens occasionally with brownish spots dorsally. Body wall covered with large, thick scale-like plates covered by a thin membrane. Each scale or plate have a narrowed end, which project forward in anterior body and backward in posterior body. Tentacles 10, in single circle, two mid-ventral tentacles smaller. Color of tentacles and introvert yellowish or brownish white in living and preserved specimens, living specimens occasionally with small brownish spots also on tentacles. Oral-valves undeveloped or devoid. Pedicels retractile, in two ill-defined rows along each radius throughout body length, lacking on introvert and posterior tip, up to 25 pedicels in each row, sparse dorsally. Ventral pedicels with suckershaped tips, becoming gradually smaller anteriorly and posteriorly. Color of pedicels same as adjacent body wall. Five anal papillae and five anal teeth in radii.
Calcareous ring simple, short (Fig. 2D); radial and inter radial elements solid, not fragmented. Both radial and inter radial plates with anterior projections and posterior depression; radials anteriorly bifid. Polian vesicle and stone canal single. Several rows of short villi-like projections surrounding oral opening. Gonad in anterior to middle body, in two clusters, one on each side of dorsal mesentery; tubules with one or two branches.
External body wall ossicles comprise small, complete and incomplete baskets, the latter often appearing as Xshaped ossicles (x-bodies) (Fig. 6F, G, Table 4). Complete baskets with a cross-shaped base and four holes and a very spinous/thorny rim with spines also present on outer surface; incomplete baskets also very spinous, the spines sometimes meeting to produce a hole at end of each arm; baskets never smooth. Inner body wall with knobbed buttons (Fig. 6F, G, Table 4). Scales or plates (Fig. 6H, Table 4), pine-cone shaped, multi-layered and knobbed, with a meshed structure, each scale often narrowed at one end. Anal papillae contain supporting plates (Fig. 6I, Table 4). Skin around anus with knobbed buttons.
In tentacles, perforated plates and rod-like plates of various sizes and shapes (Fig. 6A, Table 4), sometimes plates without distal perforations, then resulting rod-shaped structures; margins nearly always somewhat spiny. Peri-oral skin with small, basket-like perforated plates with thin margins and tiny knobs (Fig. 6B, Table 4). Introvert with perforated plates (Fig. 6D, Table 4), with or without knobs. Pharyngeal villi contain narrow plates, with many marginal knobs/spines (Fig. 6C, Table 4). Gonad lacking ossicles
Pedicels with circular endplate and other supporting plates (Fig. 6E, Table 4). Endplate with approximately uniform-sized perforations. Supporting plates perforated and with spiny/knobbed margin, perforations mostly arranged in double rows.
Remarks. This species has been reported as Cucumaria tegulata Augustin, 1908, based a single specimen (length 14 mm, width 6 mm) collected from Uraga Channel, 180 m (Augustin 1908). Ohshima (1915) synonymized this species with Cucumaria capensis Théel, 1886. Thandar (1991) referred C. capensis to the genus Ocnus Forbes & Goodsir, in Forbes 1841. However, C. tegulata has multi-layerd, imbricating, scale-like ossicles covering the body wall as “tile-roofing (meaning of tegulata)” (Augustin 1908), while the plate ossicles of O. capensis are single-layered and scattered (Théel 1886), consequently different from the type and the specimens here described. Augustin (1908, Tafel II, Figur 1) provides a excellent figure of the form of this species which confirms the imbricating plates and pedicels with sucker-shaped tip. Furthermore, Ocnus is suspected by Rowe (in Rowe & Gates 1995) as strictly a European genus.
This species is characterised by 10 tentacles with two reduced ventrally, a simple calcareous ring without posterior prolongations, X-shaped ossicles (x-bodies or incomplete baskets) as external body wall deposits, scales, or scale-like plates covering the body wall, buttons in body wall, and the absence of any obvious oral valves. This combination of features is typical of the genera Hemiocnus Mjobo & Thandar, 2016, and Pseudocnella Thandar, 1987. The genus Hemiocnus has been diagnosed as having 10 tentacles with two reduced ventrally, buttons in the body wall in addition to plates, rosette ossicles in the tentacles (Mjobo & Thandar 2016); whereas Pseudocnella has 10 tentacles of more or less equal size, no button-shaped ossicles in the body wall and lack rosette ossicles the tentacles (implied restriction by Mjobo & Thandar 1987). Consequently the present specimens should be classified in the genus Hemiocnus, differing from its congeners in the presence of imbricating plates. Amongst the current species of Hemiocnus, H. tegulatus resembles H. insolens (Théel, 1886) previously included in Pseudocnella by Thandar (1987) differing in the presence of imbricating plates and better developed baskets and from H. syracusanus (Grube, 1840) in the same feature and the presence of well developed baskets.
Seven specimens of this species are also deposited in WMNH (3 specimens, WMNH-INV-2015-215–217; 1 specimen, WMNH-INV-2015-224; 3 specimens, WMNH-INV-2015-307–309), collected from off Shirahama (not from Misaki), of which a photograph of living state, based on the largest specimen (length 10 mm, width 3 mm) was prepared as “ Pseudocnus sp.?” (Okanishi et al. 2016, fig. 8 I).
Distribution. Uraga Channel, 180 m (Augustin 1908); off Goto Island, west of Kyushu, 139 fathoms (Ohshima 1915, as Cucumaria capensis Théel, 1886); off Shirahama, south coast of Wakayama Prefecture, 124– 175 m (Okanishi et al. 2016); off Jyogashima Island, south coast of Kanagawa Prefecture, sand bottom, 101–111 m, middle to western Japan.
description: Published as part of Yamana, Yusuke & Kohtsuka, Hisanori, 2018, Dendrochirotid holothurians (Echinodermata: Holothuroidea: Dendrochirotida) including four new species, from off Misaki, Japan, pp. 429-453 in Zootaxa 4455 (3) on pages 438-440, DOI: 10.11646/zootaxa.4455.3.2, http://zenodo.org/record/1457427