Apostichopus Liao, 1980

Woo, Sau Pinn, Ogawa, Akito, Tan, Shau Hwai, Yasin, Zulfigar, Kajihara, Hiroshi & Fujita, Toshihiko, 2017, A taxonomic revision of the genus Apostichopus (Holothuroidea: Stichopodidae) from Japan, Zootaxa 4350 (1), pp. 121-135 : 122-123

Genus Apostichopus Liao, 1980

Type species. Stichopus japonicus Selenka, 1867 (but see Remarks below).

Type locality. Japan

Diagnosis. Mouth ventral, surrounded by twenty peltate-shaped tentacles. Body stout and cylindrical. Conical papillae conspicuous or less conspicuous, protruding at dorsal and lateral sides of body; similar conical papillae arranged in one line at ventro-lateral sides; smaller papillae scattered on dorsal and lateral surfaces. Background body colour highly variable from red to brown and green to black. Gonads in two tufts. Spicules taking form of tables, buttons, multiperforated plates, rods, and complex plates. Dorsal body-wall spicules composed of tables; often reduced with pillars absent, but simple and not spinous if present; rims smooth or spinous. Dorsal body wall of juvenile contains tables with four spires, each having multiple spines on its end, with two to three crossbeams. Rosette and C-shaped spicules absent in dorsal body wall of both adult and juveniles. Papillae containing elongated buttons, rods, tables, and multiperforated plates. Rods in tentacles. Ventral tube feet containing multiperforated plates and tables, the latter without pillars. Spinous complex plates present in cloacal walls both in adult and juvenile.

Species composition. Apostichopus armatus ( Selenka, 1867) ; Apostichopus japonicus ( Selenka, 1867) (see Remarks).

Remarks. Liao (1980) erected this genus based on material from the northern East China Sea that was identified as Apostichopus japonicus . Judging from the drawings of the spicules, Liao’s (1980) material was most likely to represent Apostichopus armatus ( Liao 1980: fig. 1), to which Article 70.3 (Misidentified type species) of the Code (International Commission on Zoological Nomenclature 1999) applies. In order to serve stability and universality of the name, we take the option stipulated under Article 70.3.1, in which the nominal species previously cited as the type species is to be retained, because alteration of the type species will not affect the genus name usage. The diagnosis for Apostichopus given by Liao (1980) sufficiently illustrated clear separation of Apostichopus from other genera based on reduced table spicules without pillars in the body wall ( Liao 1980: fig. 1).

The absence of C-shaped spicules and the presence of reduced table spicules in the dorsal body of Apostichopus differentiate it from the genera Stichopus and Isostichopus Deichmann, 1958 , which have abundant C-shaped spicules and no reduced table in the dorsal body ( Clark 1922; Deichmann 1958). The genus Apostichopus also can be easily distinguished from the genera Thelenota Brandt, 1835 and Astichopus Clark, 1922 by the presence of table spicules that are absent in the dorsal body of the two genera ( Clark 1922). Complex plates in the cloacal walls and elongated buttons in the papillae are observed in Apostichopus ( Théel 1886; Liao 1980) and Parastichopus Clark, 1922 ( Clark 1922; Lambert 1986). The well-developed table spicules with complete spires in the dorsal body of Parastichopus are absent in adult Apostichopus (body length greater than 70 mm) ( Mitsukuri 1897). Furthermore, Apostichopus can be found from the intertidal zone to the depth of about 20‒40 m ( Zhao 2015), while Parastichopus is distributed only in deeper waters from 30 m down to the depth of 600 m ( Deichmann 1937; Lambert 1986; Imaoka et al. 1990).

We only included two species in the species list of Apostichopus . This is contrary to the inclusion of Parastichopus californicus ( Stimpson, 1857) , Stichopus johnsoni Théel 1886 , Parastichopus leukhothele Lambert, 1986 , Parastichopus multidentis Imaoka, 1991 , Stichopus nigripunctatus Augustin, 1908 , Parastichopus nipponensis Imaoka, 1990 (synonym of P. nigripunctatus ) and Stichopus parvimensis Clark, 1913 by Paulay (2013) as part of the species list in Apostichopus . The inclusion is deemed invalid because the nomenclatural act of transferring these species to the genus Apostichopus did not fulfil the requirements of Article 8 (What constitutes published work) of the Code (International Commission on Zoological Nomenclature 1999).