Pseudoceramaster doto n. sp.

Japanese name: Nise-gokaku-hitode

Nise: pseudo, gokaku: pentagonal, hitode: seastar

FIGURE 10A–G

Etymology. The species epithet doto is the Japanese word for “equal” alluding to the homogeneous granule shape on the abactinal plates. Doto is a noun held in apposition.

Diagnosis

Shape stellate (R/r=1.87), arms triangular, interradial arcs weakly curved (Fig. 10A, E). Abactinal plates polygonal to quadrate, granulate (Fig. 10B), approximately 3 counted along a 1.0 mm, 8 to 40 per plate, homogeneous in size, peripheral granules round to quadrate. Furrow spines, 6 to 8, subambulacral spines 3 (Fig. 10F, G).

Taxonomic Comments

This species was assigned to Pseudoceramaster based on the abutted, granule-covered abactinal plates plates and adambulacral armature, which showed 6 to 8 furrow spines with 3 rows of subambulacral spines, including an adjacent series of two to three short, stocky subambulacrals, and concluding with two series of adambulacral granules or short spines similar to those on Pseudoceramaster regularis as described by Jangoux (1981).

Pseudoceramaster doto n. sp. differs in that the granules on each of the abactinal plates are round to quadrate and more homogeneous in size and shape than those of Pseudoceramaster regularis, which exhibit more sharply angular peripheral granules on each plate. This species invites comparison with Pseudoceramaster misakiensis which has comparable numbers of furrow spines (6 to 7 versus 6 to 8 in P. doto n. sp.), similar subambulacral spines (two rows versus three in P. doto n. sp.) and relatively coarse abactinal granulation. Pseudoceramaster doto n. sp. differs from P. misakiensis in that it displays twice as many marginal plates per interradius, is much less stellate (R/r=1.87 versus 2.8) and shows marginal plates which are more broadly elongate in shape versus P. misakiensis which has a wider plate shape which occupies a significant fraction of the “r” distance (20%) versus 10% in Pseudoceramaster doto n. sp. Pedicellariae, which were described as “numerous” in Pseudoceramaster misakiensis are absent from Pseudoceramaster doto n. sp.

Occurrence

Okinawa and Kagoshima prefectures, southern Japan, 250– 404 m.

Description

Body stout, stellate (R/r=1.87) Abactinal surface flat, interradii weakly curved. Arms short, blunt. NSMT E-13676 smaller with more pointed arm tips. NSMT E-13682 with arm tips blunt, rounded, and heavily developed (Fig. 10A).

Abactinal plates quadrate to polygonal, abutted against one another forming pavement (Fig. 10B). Plates more polygonal to pentagonal in outline on radial regions, more quadrate, in shape and more closely arranged interradially. Plates largest proximally on disk becoming smaller and more irregularly shaped distally adjacent to superomarginals. Abactinal surface flush with superomarginal surface (Fig. 10D). Abactinal plates covered by coarse, closely-set, round to polygonal granules, uniform in size, but peripheral granules weakly quadrate, 8–40 per plate. Approximately three granules present along a 1.0 mm line. Each plate with 6–25 granules arranged around periphery of each plate with one to 18 granules, usually between 10–15 on each plate (Fig. 10B). Radial regions with more strongly developed, but still shallow fasciolar grooves which flatten out between interradial plates. Papulae present, four to six to a plate, most abundant on radial regions, but absent interradially. Abactinal plates extend onto arms, but vanish distally where penultimate superomarginals abut over the arm radius. Madreporite quadrate in shape with rounded edges, with sulci deep, flanked by 32–35 granules (approximately four to five plates). Pedicellariae not observed. Internal radiating bar-like ossicles, as observed in Mediaster or Rosaster absent.

Superomarginals 16–19 per interradius with slight variation owing to the presence of some smaller plates intercalated between the larger ones. Inferomarginals, 17–20 per interradius.

Plates rounded in cross-section, stout dorsal surface flat. Marginal plates elongate, distalmost one or two plates directly abutting over midline, especially adjacent to terminus (Fig. 10C). Spines or other prominent accessories (tubercles, etc.) absent from marginal plate surfaces. Surface of marginal plates covered by closely set, rounded, granules identical to those on the abactinal surface (Fig. 10C–D). Approximately 20 mm on each width by ~ 25 mm on each length. Central plate with approximately 400 tightly but evenly arranged granules. Distalmost two superomarginals with discrete bald patches present, occupying most of plate surface (Fig. 10C). No pedicellariae observed on marginal plates.

Actinal regions composed of approximately five or six chevron-like plate series. Two to three in ordered series with the remainder in more irregular arrangement (Fig. 10F). Plates larger proximally becoming smaller and more irregular distally. Plate outline quadrate to polygonal, each covered by round, coarse granules, 10–40 identical to those on abactinal surface, densely but evenly arranged. Granules, 10–25 forming distinct periphery with five to 20 present within the granular periphery. One or two small forceps-shaped pedicellariae present in each interradius.

Furrow spines, 6 to 8, all similar in length with tips curved, blunt (Fig. 10F, G). Furrow spines quadrate with edges rounded. Furrows separated from three series of subambulacrals by discrete space between spine series. Subambulacrals three, shorter than furrow spines, rounded, blunt each about twice as thick as furrow spines. A second series of subambulacral spines, three or four in number, lower than the first subambulacral spine series is closest with the actinal surface but set off by a discrete space. The distalmost subambulacral granule series is largely identical with other granules on the actinal surface. No pedicellariae observed on adambulacrals.

Oral plate with two elongate spines, triangular in cross-section projecting into mouth (Fig. 10F). Mouth plate furrow spines, three to five, cross-section triangular to angular quadrate. Oral plate surface covered by seven to nine short spine-like, each triangular or polygonal granules.

Material Examined

Holotype. NSMT-E-13682. Off Nago Bay, Okinawa Prefecture, Japan 26º32.18’N, 127º43.96’E, to 26º32.64’N, 127º44.29’E, 404–394 m. Coll. R/V Toyoshio-Maru St. 11. May 27, 2002. TY-02-11“Photo 2–6” 2002-072. 1 wet spec. R=4.3, r=2.3.

Paratype. NSMT-E-13676. Northwest off Amami-Oshima Island, Kagoshima Prefecture, Japan, 28º59.47 N, 127º4.91 E to 28º58.25 N, 127º4.18 E, 250 m. Coll. 7 Nov. 2003, R/V Yoko-Maru, YK03-T11, st. 11. 1 wet spec. R=3.8, r=1.7.