Pseudoplacothuria ohshimai Yamana & Kohtsuka 2018, comb. nov.
Creators: name: Yamana, Yusuke
name: Kohtsuka, Hisanori
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Dendrochirotida
Phyllophoridae
Pseudoplacothuria
Pseudoplacothuria ohshimai

description: Pseudoplacothuria ohshimai (Liao, 1997) comb. nov.
[New Japanese name: Ohshima-gumimodoki]
(Figs 1G, 2G, 9A–J)
Cucumaria mosaica: Ohshima 1915: 265.
Cucumaria mosaica: Ohshima 1918a: 279, fig. 65 a–i.
Pentamera mosaica (Ohshima non Koehler & Vaney): Panning 1949: 465.
Placothuria ohshimai Liao, 1997: 225 –227, fig. 135 (also see Liao & Pawson 2001: 85 –87).
Pentamera sp.: Okanishi et al., 2016: 23, Fig. 8K.
non: Cucumaria mosaica Koehler & Vaney, 1910: 98 –99, Pl. II, figs 1–5. = Pseudothyone mosaica (Koehler & Vaney, 1910): Panning 1949: 456.
Material examined. 1 specimen, WMNH-INV-2015-9 (St. 1, 26 August 2014, length 21 mm, width 8 mm); 1 specimen, WMNH-INV-2015-10 (St. 1, 26 August 2014, length 13 mm, width 4 mm).
Description. Body fusiform to barrel-shaped, with both ends turned upwards (Fig. 1G); body wall thin, hard and rough. Body and introvert nearest to body white or cream-white (living and preserved specimens). Tentacles and introvert nearest to tentacle base, pale brown (living and preserved specimens). Tentacles 10, in single circle, two ventral tentacles smaller. Several rows of villi-like projections surrounding oral opening, villi short and thick. Pedicels non-retractile, thin, in two rows along each radius throughout body length, lacking on introvert, mostly white or cream-white but pale brown in mid-ventral region (living and preserved animals). Pedicels become gradually smaller anteriorly and posteriorly, each row with approximately 44–60 pedicels in ventral three radii, approximately 29–37 pedicels in dorsal two radii. Five anal papillae and five anal teeth in radii.
Calcareous ring long, complex, with paired posterior, weakly fragmented prolongations; radial and interradial plates not fragmented (Fig. 2G). Radial elements elongated, each with an anterior notch. Interradial elements also long but without posterior prolongations but with slight anterior projection bearing a weakly developed notch. Polian vesicle and stone canal single. Gonad in mid-body, in two clusters, one on each side of dorsal mesentery, tubules unbranched.
Body wall ossicles as abundant two-pillared tables and lens-shaped bodies. (Fig. 9F, G, H, Table 7). Table disc basically with 4 large central perforations and approximately 10–20 smaller, marginal ones; spire low, with one cross-beam and approximately 10–12 teeth on top. Lens-shaped ossicles, biconvex, thick, mesh-like; many intermediates between the two present (Fig. 9F, G). Anal papilla with supporting tables and plates (Fig. 9I, Table 7). Supporting tables with small arched disc; low spire, with two pillars and one cross-beam and a toothed apex. Supporting plates small, irregular, and marginally branched. Skin around anus with small tables.
Tentacle deposits comprise plates of various size and shape, tables and many intermediate types between plate and rod (Fig. 9A, Table 7). Plates with 2–4 large central perforations and 2–6 smaller perforations at distal ends. Larger plates, mostly narrow, central perforations arranged in single or double series. Smaller plates, mostly broad with central perforations arranged in three or more series. Tables with broad disc with 2–4 large central perforations and approximately 8–16 small marginal ones; spire low, of two pillars with 8–12 minute processes at apex. Tentacle tables present only in one specimen (WMNH-INV-2015-9) (Table 7) and not in the other. Peri-oral skin and pharyngeal villi with small rosettes (Fig. 9B, C, Table 7). Introvert with tables (Fig. 9D, Table 7), with broad disc with approximately 10–20 perforations; a low spire of two pillars and 8–12 minute processes/teeth on top of spire.
Pedicels with endplate and supporting tables (Fig. 9E, Table 7). Endplate small, mostly with fine “mesh-like” or multilocular structure medially and large perforations at approximately regular intervals marginally, occasionally endplate results in a stellate form. Supporting tables with narrow, arched disc, with 0–4 central perforations and 1–4 distal ones; spire high, with two pillars, ending in flattened lobes and/or elongated processes/ teeth, occasionally pillars united distally, with one or two cross-beams. Gonadal tubules, (ovary and testis), with elongated, needle-shaped ossicles (Fig. 9J), with many short spinous processes on its surface, occasionally with perforations and branches.
Remarks. This species is in agreement with Ohshima's (1915 and 1918 a) description of the Japanese form of Cucumaria mosaica Koehler & Vaney, 1910, at 47 fathoms (ca. 86 m) off Suruga Bay. In the original description of C. mosaica, the ossicles of the pedicels are described as biscuit-shaped plates without spire (Koehler & Vaney 1910). However, in the current material the pedicels have supporting tables and hence are different from Koehler & Vaney’s form. Currently this species is known as Placothuria ohshimai Liao, 1997. Placothuria was a genus erected by Pawson & Fell, 1965 for some plated forms. However, the descriptions of mosaica by both Ohshima (1915 and 1918a) and Liao (1997) do not correspond with the diagnosis of the genus Placothuria by Pawson & Fell (1965). The type species of Placothuria is a well known New Zealand species previously known as Stolus huttoni Dendy, 1896 (Pawson & Fell 1965), which has flat reticulated plates (Dendy 1896) or two-layered flattened plates (Panning 1949) in body wall, and possess a calcareous ring with long posterior prolongations to both the radial and interradial elements (Pawson 1963), hence satisfying the diagnosis of Placothuria but the present material does not satisfy this description of the calcareous ring.
The external body morphology (10 tentacles with ventral two small, and 5 series of pedicels) of this species is close to that of all the species in the genus Pentamera Ayres, 1852, and ossicle morphologies (especially the shape of plates or rods in tentacles, and supporting tables in pedicels) are also close to those of several species within the genus (e.g., Lambert 1998). However, among the nominal species of Pentamera, this species is easily distinguished by the following features: body wall with thick lens-shaped ossicles, only the radial plates of the calcareous ring are elongated before bearing long, paired posterior processes whereas in the nominal species of Pentamera the radials are deeply incised and bifurcate before the posterior border of the interradial plates. Because of the presence of large lenticular plates in addition to the tables, and a different form of the calcareous ring, we refer this species to a new genus, Pseudoplacothuria. Further, P. ohshimae has needle-shaped ossicles in the gonadal tubules which need to be studied in all species of Pentamera and in Placothuria.
In WMNH, three specimens of this species have been deposited in WMNH (WMNH-INV-2015-206–208), collected from off Shirahama (not from Misaki), previously reported as Pentamera sp. with a photograph of the largest live specimen (WMNH-INV-2015-206: length 32 mm, width 5 mm) (Okanishi et al. 2016; Fig. 8 K).
Distribution. China Sea, 64–115 m (Liao 1997); Suruga Bay, 47 fathoms (ca. 86 m) (Ohshima 1915 and 1918a); off Shirahama, south coast of Wakayama Prefecture, 72–75 m (Okanishi et al. 2016); off Jyogashima Island, south coast of Kanagawa Prefecture, sand bottom, 87– 88 m.
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 447-451, DOI: 10.11646/zootaxa.4455.3.2, http://zenodo.org/record/1457427