Apostichopus japonicus

Apostichopus japonicus (Selenka, 1867)

Figs 6–13

Stichopus japonicus Selenka, 1867: 318, pl. 18, figs 33–36; Semper, 1868: 74; von Marenzeller, 1882: 136 –137, taf V, fig 11; Théel, 1886: 160, pl. VII, fig. 3; Mitsukuri 1896: 408; Augustin, 1908: 6 –7, fig. 4; Mitsukuri, 1912: 163, pl. 4, figs 32–44; Ohshima, 1915: 247 –248; Clark, 1922: 61; Choe & Ohshima, 1961: 97 –105; Levin, 1983:1 –45, figs 1–12.

Stichopus japonicus typicus Théel, 1886: 196.

Stichopus (Apostichopus) japonicus – Kanno et al., 2006: 672 –685.

Apostichopus japonicus – Kuramochi & Naganuma, 2010: 49 –54, fig. 1a, 1b, 2.

Stichopus roseus Augustin, 1908: 13 –14, fig. 10.

Type material examined. Syntype MCZ HOL –763, Northwest Pacific Ocean, Japan.

Additional materials examined. NSMT –E3673, Fukue Island, Nagasaki, 14 March 1998, T. Fujita; NSMT – 7045A, Tateyama Bay, Chiba, 21 April 2011, Y. Tamura; NSMT –E7046A, Futtsu, Chiba,4 29 June 2011, Y. Tamura; NSMT –E7046C, Futtsu, Chiba, 29 June 2011, Y. Tamura; NSMT –E7047B, Aburatsubo Bay, Kanagawa, 10 July 2011, Y. Tamura; NSMT –E7047D, Aburatsubo Bay, Kanagawa, 10 July 2011, Y. Tamura; NSMT –E7048, Uchiura Bay, Kanagawa, K. Yakiguchi, 28 September 2011; NSMT –10122A-E, 5 specimens, Takeoka, Futtsu, Chiba, K. Kawata & A. Ogawa, 24 December 2014.

Type locality. Japan.

Descriptions. Twenty peltate tentacles. Two rows of dorsal papillae, each arranged alternately in zig-zag pattern along the dorso-lateral radii. Single row of conical papillae along each ventor-lateral radius. Similar conical papillae, but larger, arranged single row at both ventro-lateral radii. Numerous, loosely arranged, small papillae scattered on dorsal and lateral body. Ventral side flattened. Tube feet arranged in 5–6 rows in central ambulacral area; 4–5 rows in both lateral ambulacra areas. Interambulcra narrow. Mouth subventral, surrounded by a ring of small papillae. Background body colour in alcohol dark reddish brown on dorsal, lighter brown on both lateral and ventral body. Gonads in two tufts; one each side of dorsal mesentery. Twenty free-hanging tentacular ampullae. Polian vesicle single, in various shapes and forms. Intestine connected to dorsal mesentery with rete mirabile.

Dorsal body wall containing tables. Tables in dorsal body wall of adult reduced, pillars absent (Figs. 7, 8). Disk of table oval to round in shape with smooth rims; 2–14 irregular perforations on disk. Tables in dorsal body of juvenile with four pillars; single spine at tip of each pillar. Papillae containing multiperforated plates, reduced tables, rods, and elongated buttons. Multiperforated plates in papillae with four central perforation and numerous peripheral perforations; rim of uneven (Fig. 9A–D). Reduced tables in papillae similar to those in dorsal body (Fig. 9E), size larger and more perforations (2–14 perforations); rims smooth to uneven, but not spinous. Elongated buttons in papillae having two longitudinal rows of 5–11 perforations (Fig. 10A). Rods in papillae straight to curved; surface spinous (Fig. 10B). Rods in tentacles curved; surface covered with multiple spinelets (Fig. 11A–C). Tube feet with multiperforated plates (Fig. 12). Cloacal wall containing oval to rounded complex plates; surface very spinous and knobby (Fig. 13).

Distribution. Shallow temperate waters in the coasts of China, Japan, Korea and Russia. Northern distribution limit at Sakhalin Island, Russia and Southern limit in the Kagoshima prefecture in Japan (see Zhao 2015) Remarks. The reduced table spicules of other materials examined in the dorsal body are similar to the spicules named “hemmungsbildungen” meaning table spicules reduced to the ring in Selenka (1876: pl. 18, fig. 36). The most contrasting difference between A. japonicus and A. armatus can be seen in the rims of reduced tables found on the dorsal body. The reduced tables have only smooth and non-spinous rims in A. japonicus compared to spinous disk rim tables in A. armatus. Observations on the reduced table spicules of type material using SEM (Fig. 7) confirms that the rims of reduced table spicules in the dorsal body are smooth and non-spinous. Kuramochi & Naganuma (2010) also observed similar characters at rim of tables in materials they examined. Although the figures of reduced tables of A. japonicus observed under compound microscope in Kuramochi & Naganuma (2010: fig. 2) showed that the rim of disks in tables appear to be spinous, greater resolution observation using scanning electron microscope in this study revealed that the rim on the disks of the reduced tables are merely undulating on the rims but do not form spines.