Pseudoplacothuria ohshimai ( Liao, 1997 )

Yamana, Yusuke & Kohtsuka, Hisanori, 2018, Dendrochirotid holothurians (Echinodermata: Holothuroidea: Dendrochirotida) including four new species, from off Misaki, Japan, Zootaxa 4455 (3), pp. 429-453: 447-451

publication ID

publication LSID

persistent identifier

taxon LSID

treatment provided by


scientific name

Pseudoplacothuria ohshimai ( Liao, 1997 )

comb. nov.

Pseudoplacothuria ohshimai ( Liao, 1997)  comb. nov.

[New Japanese name: Ohshima-gumimodoki]

( Figs 1GView FIGURE 1, 2GView FIGURE 2, 9A–JView FIGURE 9)

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. 8KView FIGURE 8.

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. 1GView FIGURE 1); 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. 2GView FIGURE 2). 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, HView FIGURE 9, 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, GView FIGURE 9). Anal papilla with supporting tables and plates ( Fig. 9IView FIGURE 9, 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. 9AView FIGURE 9, 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, CView FIGURE 9, Table 7). Introvert with tables ( Fig. 9DView FIGURE 9, 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. 9EView FIGURE 9, 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. 9JView FIGURE 9), 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 WMNHAbout WMNH, three specimens of this species have been deposited in WMNHAbout 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 KView FIGURE 8).

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.


Wakayama Prefectural Museum of Natural History














Pseudoplacothuria ohshimai ( Liao, 1997 )

Yamana, Yusuke & Kohtsuka, Hisanori 2018


Cucumaria mosaica:

Ohshima 1915 : 265


Cucumaria mosaica:

Ohshima 1918a : 279


Pentamera mosaica

Panning 1949 : 465


Placothuria ohshimai

Liao, 1997 : 225 Liao & Pawson 2001 : 85



Okanishi et al., 2016 : 23