Coelorinchus japonicus ( Temminck & Schlegel, 1846 )

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 76-84

Coelorinchus japonicus ( Temminck & Schlegel, 1846)

[Japanese name: Tojin]

( Figs. 48–51 , 52A , 53 A–B, 54A; Appendix 3-3A)

Macrourus japonicus Temminck & Schlegel, 1846:256 , pl. CXII, figs. II, IIa, IIb [original description; in part; lectotype: RMNH 3746, from “bays in provinces Oomura and Shimabara” (Nagasaki Pref.)]; Boeseman 1947:184 (in part; lectotype designation; re-examination of type specimens).

Macrurus japonicus : G̹nther 1862:395 [brief description; 2 spec. (only heads) from Japan]; G̹nther 1887:127 [brief description; 1 spec. from off Inoshima (= Eno-shima Island), Sagami Bay, Challenger sta. 232]; Steindachner & D̂derlein 1887:283 (brief description; 1 spec. probably from Sagami Bay ); Doflein 1906:234, unnumbered fig. (spec. from Sagami Bay).

Coelorhynchus japonicus : Jordan & Snyder 1901:120 (listed; Japan; local name “Hige”); Jordan & Gilbert in Jordan & Starks 1904:617 (description; 8 spec. from Misaki and Nagasaki); Franz 1910:26 (12 spec. from Yokohama and Aburatsubo); Jordan et al. 1913:418 (listed; Japan; Japanese names: “Hige” or “Tōjin”); Gilbert & Hubbs 1916:178 (supplementary description; 4 spec. from off Cape Shionomisaki and Suruga Bay); Izuka & Matsuura 1920:103 (spec. from “ Tōkyō Market”); Jordan & Hubbs 1925:327 (spec. from Misaki); Tanaka 1927:477, fig. 923 (compiled; Japan; standard Japanese name:“Tojin”); Schmidt 1931:155 (brief description; 1 spec. from Nagasaki); Kamohara 1934a:54 (listed; Kochi); Kamohara 1934b:301 (1 spec. from Susaki, Kochi Pref.); Okada & Matsubara 1938:450 (in key; Japan); Kamohara 1938:73 (4 spec. from Kochi Pref.); Kamohara 1950:276, fig. 211 (listed; Kochi and Wakayama Pref.); Tanaka 1951:137, fig. 350 (compiled; Japan); Kuroda 1951:391 (listed; Suruga Bay); Uchinomi 1951:76 (listed; southern part of Kii Peninsula); Kamohara 1952:99 (spec. from Kochi Pref.); Asano et al. 1952:97 (listed; Ibaraki Pref.); Kamohara 1955:63, pl. 63, fig. 2 (compiled; Japan); Matsubara 1955:1313 (in key; Japan); Kobayashi 1956:72 (listed; Enshu-nada); Kamohara 1958:73 (listed; Kochi Pref.); Kamohara 1961a:63, pl. 63, fig. 2 (compiled; Japan); Kamohara 1964:96 (listed; Kochi Pref.); Tatara et al. 1965:121 (listed; off Shikoku); Matsubara 1965:506 (compiled; Japan); Dotsu & Tomiyama 1967:35 (spec. from Goto Islands); Kamohara 1967:125, pl. 63, fig. 2 (compiled; Japan); Okamura 1970a:183, pl. XL, text-figs. 78–79 (description; biological notes; 93 spec. from Pacific off southern Japan from Sagami Bay to Mimase); Tominaga & Uyeno 1981:488 (listed; Japan); Yatou 1982:181, 353, fig. 106 (description; 8 spec. from Tosa Bay; photo based on BSKU 29937); Ohta 1983: table A (listed with a question mark; Suruga Bay; in situ observation); Akazaki 1984:265 (listed; Aoshima, Miyazaki Pref.).

[?] Coelorhynchus parallelus (not G̹nther 1877): Kuroda 1941:80, fig. 11 (brief description; 2 spec. from Suruga Bay) [reidentified from figure]; Kuroda 1951:392 (listed; Suruga Bay); Kuroda 1962:8 (description of fresh color; 1 spec. from Suruga Bay).

Coelorhynchus (Oxymacrurus) japonicus : Okamura 1970b: table 1 (listed; Japan).

Coelorinchus japonicus : Yatou 1984:231, 367, fig. 163 (brief description; 5 spec. from Okinawa Trough; photo based on BSKU 29886); Okamura 1984b:97, pl. 83, fig. D (compiled); Kamohara & Okamura 1985:32, pl. 31, fig. 154 (compiled; Japan); Okamura 1988:97, pl. 83, fig. D (compiled); Iwamoto 1990:162, fig. 378 (synopsis); Hori 1996:28 (listed; Ibaraki Pref.); Suzuki & Kataoka 1997:84, pl. 33, fig. 182 (brief description; 1 spec. from Kumano-nada); Okamura 1997:127, fig. 14 (compiled); Funabashi 1998:85 (listed; Ibaraki Pref.); Youn 2002:539 (questionable; listed; Korea); Shao et al. 2008b: table 2 (3 spec. listed from northeastern Taiwan); Nakabo & Kai 2013:510 (in key; Japan); Ikeda & Nakabo 2015:322, pl. 68, fig. 12 (brief description; spec. from Wakayama Pref.); Iwamoto et al. 2015:57 (brief description; 7 spec. from northeastern Taiwan); Miyazaki et al. 2019: table1 (1 spec. listed from Tokyo Submarine Canyon); Motomura 2020:38 (listed; Japan).

Caelorinchus japonicus : Nakabo 1993:369 (in key; Japan); Shao 1993:169, fig. 37-7 (compiled; Taiwan; photo spec. is C. leptorhinus ); Shinohara & Matsuura 1997:290 (listed; Suruga Bay); Nakabo 2000:433 (in key; Japan); Shinohara et al. 2001:305 (listed; Tosa Bay); Nakabo 2002:43 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Nakajima 2003:55, pl. 15, fig. 90 (brief description; 1 spec. from Enshu-nada); Yamaguchi & Machida 2003:240, pl. 26, fig. 97 (comments on type specimens); Shinohara et al. 2005:416 (8 spec. listed from Ryukyu Islands); Kim et al. 2005:172, fig. 292 (compiled; Korea; photo spec. represents C. multispinulosus ); Senou et al. 2006:420 (listed; Sagami Sea); Shinohara et al. 2009:708 (listed; Pacific off Tohoku); Furuhashi et al. 2010: table 2 (44 spec. listed from northern Okinawa Trough); Iwatsuki et al. 2017:32 (listed; Hyuganada).

Caelorinchus (Oxymacrurus) japonicus : Chiou et al. 2004a: table 1 (listed; Taiwan).

Coelorinchus parallelus (not G̹nther 1877): Ikeda & Nakabo 2015:321, pl. 68, figs. 7–11 (brief description; spec. from Wakayama Pref.) [re-identified from figures].

Coelorinchus sp .: Ikeda & Nakabo 2015:322, pl. 69, figs. 1–5 (brief description; 1 spec. from Kii Channel off Wakayama Pref.; new Japanese name: “ Minabe-sokodara ”).

Diagnosis. Light organ externally represented by short, narrow, naked streak immediately anterior to anus, its anterior margin falling far short of line connecting inner pelvic-fin bases. Underside of head almost completely scaled, except for narrow naked area above upper lip and anterior portions of mandibular rami; top of snout fully scaled. Snout long, sharply pointed, length 67–90% PRL; dorsal profile of snout concave in lateral view(rarely almost straight in large specimens); terminal scute moderately short, diamond-shaped, dorsoventrally flattened; lateral nasal ridge completely supported by nasal bone. Anus slightly separated from anal-fin origin. Premaxillary teeth small, conical, arranged in short, uniformly wide band, with outer series enlarged; posterior margin of tooth band falling far short of lateral corner of mouth. Body scales covered with short, reclined, keel-like spinules in widely divergent, coarsely saw-toothed ridges; every spinule row complete, extending to posterior scale margin; spinules in each row greatly overlapping, increasing in height posteriorly; buttresses narrowly developed. Occipital scales covered with single (rarely 2–3 narrowly divergent) saw-toothed row of keel-like spinules. Transverse scale rows below second dorsal-fin origin 5–7.5. Orbit diameter 39–52% PRL; suborbital width 18–23% PRL; internasal width 26–33% PRL; interorbital width 31–38% PRL; pectoral-fin length 55–71% PRL. Body generally dark, without prominent markings; lips white; oral cavity blackish; gular membrane pale; branchiostegal membranes darker posteriorly; fins blackish.

Material examined. 48 specimens. Lectotype of Macrourus japonicus : * RMNH 3476 (33+ cm TL, fide Boeseman 1947:184; examination based on only photographs; Fig. 49A ), bays in provinces Omura and Shimabara , Nagasaki Pref., Japan , East China Sea , coll. P.F. von Siebold. Non-types: Japan: BSKU 106780 (1, 96.0 mm HL, 320+ mm TL), southeast of Shimokoshikijima Island , East China Sea , 31.5560ºN, 129.8847ºE, 415 m, F/ V Maruko-maru, tr. 4, bottom trawl, coll. N. Nakayama et al., 24 Apr. 2012 ; BSKU 26863 (1, 135 mm HL, 421+ mm TL), north-northwest of Amami-oshima Island , Okinawa Trough, 29.7850ºN, 128.4467ºE, 1000 m, F/ V Yuryo-maru, No. 8, tr. 17, bottom trawl, coll. Y. Kinoshita and S. Hagino, 3 Feb. 1978 ; BSKU 27111 (1, 105 mm HL, 322+ mm TL), northwest of Amami-oshima Island , Okinawa Trough, 29.3833ºN, 127.5150ºE, 650 m, F/ V Yuryo-maru, No. 8, tr. 21, bottom trawl, coll. Y. Kinoshita and S. Hagino, 5 Feb. 1978 ; * BSKU 109017 (1, 128 mm HL, 485+ mm TL), west of Okikasayama Bank , 32.1503ºN, 129.0072ºE, 499–504 m, T/ V Nagasakimaru, cr. N365, sta. C5, 3-m ORE beam trawl, coll. N. Nakayama, 19 Nov. 2012 ; * BSKU 43971 (1, 188 mm HL, 710+ mm TL), off Kamikawaguchi, Tosa Bay , long line, 26 Aug. 1987 ; * BSKU 115479 (1, 122 mm HL, 403+ mm TL), off Aki, Tosa Bay , 550 m, F/ V Tsukasa-maru, rod and reel, coll. T. Yamasaki, 6 Jul. 2014 ; * BSKU 45514 (1, 222 mm HL, 665+ mm TL), off Tosa-Shimizu, long line, 31 Aug. 1988 ; * BSKU 77919 (1, 34.2 mm HL, 126 mm TL), south of Muroto , 33.0790ºN, 134.1645ºE, 414– 513 m, R/ V Tansei-maru, cr. KT-05-29, sta. K-500, beam trawl, coll. H. Endo et al., 17 Nov. 2005 ; BSKU 32426 (1, 127 mm HL, 468+ mm TL), BSKU 32430 (1, 119 mm HL, 410+ mm TL), off Nahari, Tosa Bay , 33.2792ºN, 133.8947ºE, 450–470 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, sta. 1-L3, long line, coll. Y. Ishida and T. Araya, 17 Nov. 1979 ; BSKU 69780 (1, 82.8 mm HL, 279+ mm TL), Tosa Bay , 33.1900ºN, 133.6883ºE, 542–585 m, FRV Kotaka-maru, otter trawl, coll. H. Endo, 22 Jan. 1998 ; BSKU 44419 (1, 106 mm HL, 337+ mm TL), BSKU 44420 (1, 128 mm HL, 416+ mm TL), BSKU 44423 (1, 117 mm HL, 377+ mm TL), Tosa Bay , 600 m, FRV Kotaka-maru, otter trawl, 11 Jan. 1988 ; BSKU 71583 (1, 38.8 mm HL, 150+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 9 May 2000 ; BSKU 112040 (1, 49.5 mm HL, 172+ mm TL), BSKU 112044 (1, 51.0 mm HL, 163+ mm TL), BSKU 112046 (1, 31.3 mm HL, 116+ mm TL), BSKU 112049 (1, 91.4 mm HL, 285+ mm TL), BSKU 112051 (1, 63.4 mm HL, 228+ mm TL), BSKU 112052 (1, 62.7 mm HL, 177+ mm TL), BSKU 112054 (1, 109 mm HL, 400+ mm TL), BSKU 112070 (1, 45.0 mm HL, 136+ mm TL), BSKU 112074 (1, 99.1 mm HL, 343+ mm TL), Tosa Bay , 33.1428ºN, 133.6248ºE, 450–490 m, FRV Kotaka-maru, 1 Aug. 1988 ; BSKU 43816 (1, 71.0 mm HL, 247+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, 11 Jun. 1987 ; BSKU 65948 (1, 86.6 mm HL, 275+ mm TL), BSKU 97955 (1, 72.4 mm HL, 261+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 9 May 2000 ; BSKU 43977 (1, 90.5 mm HL, 327+ mm TL), Tosa Bay , 500 m, FRV Kotaka-maru, otter trawl, 20 Apr. 1987 ; BSKU 44422 (1, 118 mm HL, 448 mm TL), Tosa Bay , 600 m, FRV Kotaka-maru, otter trawl, 11 Jan. 1988 ; BSKU 23288 (1, 150 mm HL, 486+ mm TL), Mimase fish market, bottom trawl, date unknown ; BSKU 110136 (1, 134 mm HL, 487 mm TL), BSKU 110138 (1, 97.7 mm HL, 367+ mm TL), Suruga Bay , 34.7619ºN, 138.4811ºE, 196–387 m, F/ V Hinode-maru, sta. 5, bottom trawl, coll. N. Nakayama and R. Misawa, 23 Apr. 2013 ; BSKU 110084 (1, 80.2 mm HL, 243+ mm TL), BSKU 110085 (1, 77.7 mm HL, 282 mm TL), BSKU 110119 (1, 120 mm HL, 449+ mm TL), BSKU 110120 (1, 122 mm HL, 428 mm TL), Suruga Bay , 34.7489ºN, 138.4664ºE, 200–450 m, F/ V Hinode-maru, sta. 6, bottom trawl, coll. N. Nakayama and R. Misawa, 23 Apr. 2013 ; BSKU 110032 (1, 88.5 mm HL, 334 mm TL), BSKU 110033 (1, 62.6 mm HL, 193+ mm TL), BSKU 110035 (1, 88.0 mm HL, 300+ mm TL), Suruga Bay , 34.7127ºN, 138.4553ºE, 262–434 m, F/ V Hinode-maru, sta. 1, bottom trawl, coll. N. Nakayama and R. Misawa, 23 Apr. 2013 ; KPM-NI 28790 (1, 152 mm HL, 514+ mm TL), ca. 22 km south-southeast of Mie-shima Island , Kumano-nada, 34.0713ºN, 136.6453ºE, 606–669 m, R/ V Tansei-maru, cr. KT-10-16, sta. SK-1, 3-m beam trawl, coll. T. Sato, 14 Aug. 2010 ; FRLM 2535 (1, 130 mm HL, 419+ mm TL), off Mie, Kumano-nada, long line, coll. Fisheries Research Institute of Mie Pref., 16 Apr. 1980 ; * BSKU 110419 (1, 29.0 mm HL, 112+ mm TL), Suruga Bay , 34.7489ºN, 138.4664ºE, 200–450 m, F/ V Hinode-maru, sta. 6, bottom trawl, coll. N. Nakayama and R. Misawa, 23 Apr. 2013 ; KPM-NI 13883 (1, 140 mm HL, 518+ mm TL), off Zushi, Sagami Bay , 500 m, hook and line, coll. M. Miyazawa, 14 Mar. 2004 ; BSKU 103027 (1, 137 mm HL, 454+ mm TL), Sagami Bay, 950 m, rod and reel, coll. T. Okamoto, 18 Apr. 2010 ; KPM-NI 12824 (1, 149 mm HL, 528+ mm TL), off Odawara, Sagami Bay, 450 m, hook and line, 15 Mar. 2003 ; KPM-NI 12080 (1, 126 mm HL, 468+ mm TL), off Fukuura, Sagami Bay, 350 m, hook and line, 8 Apr. 2002 ; KPM-NI 19322 (1, 172 mm HL, 630+ mm TL), west of Nii-jima Island, Izu Islands, 400 m, hook and line, coll. H. Ishikawa, 14 Jun. 2007.

Counts and measurements. Based on 41 specimens (31.3–172 mm HL, 116+–630+ mm TL). Counts: first dorsal-fin rays II,8–10; pectoral-fin rays i17–i20; pelvicfin rays 7; gill rakers on first arch (outer/inner) 0–1/6– 9, on second arch 6–8/7–9; longitudinal scales 37–48; transverse scale rows below first dorsal-fin origin 5.5–8, below first dorsal-fin midbase 4–6.5, below second dorsal-fin origin 5–7.5, above anal-fin origin 17–28.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 40–47 (67–90); orbit diameter 22–30 (39–52); postorbital length 28–36 (49–61); postrostral length 53–60; orbit–preopercle distance 30–38 (52–64); suborbital width 10–14 (18–23); upper-jaw length 23–29 (41–49); length of rictus 17–23 (31–41); length of premaxillary tooth band 11–15 (19–26); preoral length 35–45 (58–84); length of terminal snout scute 5–9 (8–17); length of lateral nasal ridge 25–34 (42– 63); length of suborbital ridge 91–97 (152–182); snout width 23–29 (38–52); internasal width 15–19 (26–33); interorbital width 17–22 (31–38); occipital width 7–11 (13–19); body width over pectoral-fin bases 32–48 (57– 85); body depth at first dorsal-fin origin 40–55 (72–99); body depth at anal-fin origin 30–47 (53–82); prepelvic length 103–118 (178–207); preanus length 127–147 (221– 256); preanal length 130–154 (225–268); isthmus–pelvic distance 22–33 (38–57); isthmus–anus distance44–68 (81– 117); isthmus–anal distance 48–74 (88–127); pelvic–anal distance 25–47 (43–82); anus–anal distance 4–9 (8–16); pelvic-fin length 28–48 (47–83); pectoral-fin length 31–41 (55–71); predorsal length 105–112 (180–202); height of first dorsal fin 35–42 (62–74); length of first dorsal-fin base 12–19 (22–32); interdorsal length 18–30 (32–49); length of gill slit 10–13 (17–23); length of posterior nostril 7–9 (11–16); barbel length 7–11 (12–18).

Size. Attains about 93 cm TL (FRLM 3456, 927+ mm TL, Kumano-nada, Japan).

Distribution. Restricted to Japan and Taiwan. So far known only from the Pacific off southern Japan northward to Hitachi (36.60ºN; Ibaraki Pref.) and the Okinawa Trough, at depths of 150–1000 m ( Shao et al. 2008b; this study; Appendix 3-3A). Very common in the east of the Boso Peninsula (139.89ºE).

Comments on type specimens. Coelorinchus japonicus was the first grenadier species described from the North Pacific. It was originally described as Macrourus japonicus in the Pisces volume of the Fauna Japonica written by Coenraad J. Temminck and Hermann Schlegel. This outstanding monograph was published separately in 16 fascicles from 1842 to 1850, and the description of C. japonicus (pp. 256–258) appeared in the 15th fascicle published in 1846 (fide Sherborn & Jentink 1895; Yamaguchi & Machida 2003:93). The specimens examined by Temminck and Schlegel were collected by Philipp F. von Siebold and Heinrich B̹rger (see also the Introduction). To record fresh coloration, many of B̹rger’s specimens were drawn by Keiga Kawahara, a Japanese artist who produced 260 figures of fishes in response to B̹rger’s order ( Yamaguchi & Machida 2003:89). The plates and color descriptions of Temminck & Schlegel are based largely on Kawahara’s unpublished drawings, which are currently available online (Nagasaki Museum of History and Culture 2015; Naturalis 2020; Wikimedia Commons 2020).

According to Temminck & Schlegel (1846:257), C. japonicus was described from a single specimen (about one ft TL) collected from Nagasaki. This specimen was also illustrated in their monograph (pl. CXII, figs. II, IIa, IIb; see also Fig. 50A ), but its catalog number was not indicated in the original description. About a century after the Fauna Japonica, Boeseman (1947) re-examined fish specimens collected by von Siebold and B̹rger, reviewing the type materials of the species described by Temminck & Schlegel. According to Boeseman (1947:184), there were three specimens referable to C. japonicus in the ichthyological collection of the Rijksmuseum van Natuurlijke Histoire, Leiden (now the Naturalis Biodiversity Center), of which one is preserved in alcohol (RMNH 3476, Fig. 49A ) and the other two are stuffed (RMNH 1405 and RMNH 1406, Fig. 49 B–C). Boeseman considered these three specimens to be conspecific and the type series of C. japonicus , designating RMNH 3467 as the lectotype. The remaining two specimens automatically became paralectotypes under Art. 74.1.3 of the ICZN (1999), although no indication was given by Boeseman. However, as mentioned above, Temminck & Schlegel (1846) noted that their description was based on only a single specimen, and thus Boeseman’s treatment of the type materials contradicts Temminck & Schlegel’s statement.

Another problem is also included in the description and figures of C. japonicus provided by Temminck & Schlegel (1846). Although the C. japonicus specimens examined in this study generally agreed with the original description of this species, significant differences were found in coloration. Temminck & Schlegel (1846:258) described the species as having prominent, circular, grayish-blue spots on the lateral surface of the body. The characteristic spots are also depicted in their color figure (pl. CXII, fig. II). However, none of the specimens examined in this study had such body markings. The color of the first dorsal, pectoral, and pelvic fins is also significantly different. In Temminck & Schlegel’s figure, these fins are illustrated as pale except for a dark line along the second spinous ray of the first dorsal fin, whereas in the specimens examined in this study, these fins were generally uniformly dark.

While the author had no opportunity to directly examine the type series of C. japonicus , their photographs were provided by Dr. Yoshihiko Machida, a Professor Emeritus of Kochi University ( Fig. 49 ). Based on the photograph ( Fig. 49A ), RMNH 3467 corresponds with what many authors have called C. japonicus . Unfortunately, both stuffed specimens (RMNH D1405 and RMNH D1406; Fig. 49 B–C) are in poor condition, with limited information available on their identification. However, they appear to be a species of the C. argentatus group (see the Relationships of C. formosanus ) and most likely to be C. multispinulosus Katayama, 1942 . This suggestion is further supported by Kawahara’s drawing for one of the two stuffed specimens ( Fig. 50B ). His drawing agrees in all respects with fresh specimens of C. multispinulosus ( Fig. 72 ), viz., general appearance, body markings, and fin color. Therefore, there is little doubt that the two stuffed specimens do not represent C. japonicus but C. multispinulosus .

As mentioned above, Temminck & Schlegel (1846:257) stated that the original description of C. japonicus was based on a single specimen of about one ft TL. Considering the size of the specimen, it must correspond to the alcohol preserved specimen RMNH 3476 (ca. 33+ cm TL, fide Boeseman 1947:184). Temminck & Schlegel’s figures (figs. II, IIa, IIb in pl. CXII) are also considered to be based on this specimen, because they capture the presence of numerous tiny scales on the underside of the head (vs. absent in C. multispinulosus ). However, it is also clear that they complemented the color of the figure with Kawahara’s drawing that illustrates either RMNH 1405 or RMNH 1406 (= C. multispinulosus ). Therefore, the original description is based substantially on two specimens, which means that Boeseman’s (1947) use of the term “ lectotype ” is correct. For convenience, both RMNH 1405 and RMNH 1406 are recognized here as paralectotypes, although it is still uncertain which specimen was drawn by Kawahara.

Remarks. For further morphological information see Okamura (1970a). Coelorinchus japonicus is one of a few grenadier species recorded from the Sea of Japan.Although many authors listed the species from the area (e.g., Kikuchi 1931; Katayama 1940; Mori 1952, 1956; Tsuda 1964), no voucher specimens exist in museum collections, and these records appear to represent misidentified C. multispinulosus . These misidentifications are probably due to the fact that the color figure given in the original description exhibits mixed characters of C. japonicus and C. multispinulosus (as discussed above). In addition, prior to Okamura (1970a) who provided a review of all the then-known Japanese grenadiers, C. japonicus was often illustrated as having fine dark vermiculations dorsally on the body (e.g., Tanaka 1927: fig. 923; Kamohara 1950: fig. 211; Matsubara 1965: fig. 1434). Coelorinchus multispinulosus is occasionally found on the continental shelf north of southern Honshu, dominating the grenadier specimens from the Sea of Japan (based on the museum collections examined).

Ueno (1965, 1971) recorded C. japonicus from off the Pacific coast of Hokkaido, but it appears to represent C. gilberti Jordan & Hubbs, 1925, a species often found in the area. Maeda & Maruyama (1991), Maeda & Tsutsui (2003), and Nakabo & Kai (2013:1874) also doubted Ueno’s records of C. japonicus . Similarly, Amaoka et al. (2020) recently listed C. japonicus from Hokkaido, but their photographed specimen (fig. 223) likely represents C. gilberti .

A large individual of Coelorinchus sp. reported by Ikeda & Nakabo (2015:70, 322, pl. 69, figs. 1–5; WW 9706, 649 mm TL) is considered here an unusual variant of C. japonicus , because their brief description and several figures of the specimen agree well with the diagnosis of the latter species, except that the snout tip is distinctly rounded in dorsal view. The snout is usually sharply pointed in C. japonicus when viewed dorsally, but its tip is occasionally rounded in the large specimens examined ( Fig. 51 ), possibly due to damage during early ontogeny. Unfortunately, Ikeda & Nakabo’s (2015) specimen has been processed to be transferred to the Wakayama Prefectural Museum of Natural History, Wakayama (WW), and the present author had no access to the specimen in the course of this study. A direct examination of the voucher specimen is needed to determine the taxonomic status of this ambiguous individual.

Weber (1913) reported C. japonicus from Indonesia, including the Flores Sea, Bali Sea, Makassar Strait, and Arafura Sea. Subsequently, Gilbert & Hubbs (1920:488) cited Weber’s C. japonicus in the synonymy of their new species, C. acantholepis Gilbert & Hubbs, 1920 .

Okamura (1970a:186) considered C. japonicus to be widely distributed in tropical and subtropical waters of the Indo-West Pacific. However, Iwamoto (1990:163) claimed that there were no voucher specimens that would support such a distribution, and this species is regarded here as restricted to the northwestern Pacific off Japan and Taiwan.

Relationships. Coelorinchus japonicus belongs to a group of Coelorinchus species characterized by the following combination of features: light organ short, extending from anus to far posterior to pectoral-fin bases; lateral nasal ridge completely supported by nasal bone, not strongly convex when viewed dorsally; premaxillary teeth in short, uniformly wide band; underside of head mostly or almost entirely scaled; body scales covered with widely divergent rows of keel-like spinules, and every row complete throughout; buttresses of body-scale spinules scarcely to narrowly developed; no prominent markings on body ( Nakayama & Endo 2017; this study). This group corresponds with one of two subgroups of the C. japonicus group as redefined by Nakayama & Endo (2017), comprising the following nine species in which the underside of the head is completely or almost completely scaled: C. charius Iwamoto & Williams, 1999 from off Western Australia; C. commutabilis Smith & Radcliffe in Radcliffe, 1912 from the Philippines; C. japonicus ; C. leptorhinus Chiou, Shao & Iwamoto, 2004 from Taiwan; C. macrorhynchus Smith & Radcliffe in Radcliffe, 1912 from the Philippines and Australia; C. nox sp. nov. described here; C. sereti Iwamoto & Merrett, 1997 from the tropical southwestern Pacific; C. smithi Gilbert & Hubbs, 1920 from Japan to Australia; C. supernasutus McMillan & Paulin, 1993 from Australia and New Zealand. This group is called here the C. japonicus group (sensu stricto) for convenience of comparison.

Coelorinchus flabellispinis ( Alcock, 1894) , C. lasti Iwamoto & Williams, 1999 , and C. trunovi Iwamoto & Anderson, 1994 , all known from the Indian Ocean, share most of the above-mentioned features. However, the lateral nasal ridge of these three species is incompletely supported by the nasal bone. Coelorinchus flabellispinis and C. lasti also lack any external evidence of the light organ anterior to the anus.

Comparisons. Coelorinchus japonicus is a distinctive species of the C. japonicus group (sensu stricto) that readily differs from its similar congeners in that the occipital scales are covered with a single row of spinules [rarely 2–3 rows ( Fig. 52A ) vs. 4 or more widely divergent rows ( Fig. 52B )]. In addition, it differs notably from C. leptorhinus in having ventral surfaces of the head almost completely scaled (vs. underside of snout mostly naked); and from C. supernasutus in having a distinctly shorter snout (67–90% PRL vs. Ż111%).Young specimens of C. japonicus are easily distinguished from those of C. charius and C. smithi by the absence of dark saddles on the tail [ Fig. 54A vs. present in C. charius (see Iwamoto & Williams 1999:135, fig. 9b) and C. smithi ( Fig. 54B )].

Figures

FIGURE 48. Fresh specimens of Coelorinchus japonicus. (A) BSKU 77919, 34.2 mm HL, 126 mm TL, south of Muroto, Kochi Pref., Pacific, 414–513 m depth; (B) BSKU 106780, 96.0 mm HL, 320+ mm TL, southeast of Shimokoshiki-jima Island, Kagoshima Pref., East China Sea, 415 m depth; (C) BSKU 103027, 137 mm HL, 454+ mm TL, Sagami Bay, Pacific; (D) BSKU 115479, 122 mm HL, 403+ mm TL, Tosa Bay off Aki, Kochi Pref., Pacific, 550 m depth; (E) BSKU 43971, 188 mm HL, 710+ mm TL, Tosa Bay, Pacific. Lateral views. [Photos: (A–D) N. Nakayama; (E) BSKU]

FIGURE 49. Type specimens of Macrourus japonicus (= Coelorinchus japonicus) collected from Nagasaki Pref., East China Sea. (A) RMNH 3476, lectotype; (B) RMNH D1405, paralectotype; (C) RMNH D1406, paralectotype. (A) Preserved in ethanol; (B–C) stuffed. Lateral views. [Photos: Y. Machida]

FIGURE 50. Illustrations showing type specimens of Macrourus japonicus (= Coelorinchus japonicus). (A) Figures provided in the original description (Temminck & Schlegel 1846: pl. CXII, figs. II, IIa, IIb); (B) drawing by Keiga Kawahara. [Photos: (A) Faculty of Science Common Library, Kyoto University; and (B) Naturalis Biodiversity Center, Leiden; these images were cropped from originally digitized versions.]

FIGURE 51. Preserved specimen of Coelorinchus japonicus. BSKU 45514, 222 mm HL, 665+ mm TL, off Tosa-Shimizu, Kochi Pref., Pacific. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]

FIGURE 52. Photographs showing spinulation of the occipital scales in two species of Coelorinchus. (A) C. japonicus, BSKU 44422, 118 mm HL; (B) C. smithi, BSKU 65947, 97.2 mm HL. Preserved specimens. [Photos: N. Nakayama]

FIGURE 53. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of three species of the Coelorinchus japonicus group. (A–B) C. japonicus, BSKU 109017, 128 mm HL; (C–D) C. leptorhinus, BSKU 99870, 96.5 mm HL; (E–F) C. smithi, BSKU 65947, 97.2 mm HL. (A, C, E) Views from above; (B, D, F) oblique views. [Photos: NSMT]

FIGURE 54. Preserved juvenile specimens of two species of Coelorinchus. (A) C. japonicus, BSKU 110419, 29.0 mm HL, 112+ mm TL, Suruga Bay, (B) C. smithi, BSKU 71585, 34.5 mm HL, 123+ mm TL, Tosa Bay. Lateral views. [Photos: N. Nakayama]

FIGURE 72. Fresh specimens of Coelorinchus multispinulosus. (A–C) BSKU 112572, 52.4 mm HL, 230+ mm TL, Etomo fish market, Shimane Pref., Sea of Japan; (D–F) BSKU 95364, 57.3 mm HL, 227+ mm HL, Mimase fish market, Kochi Pref., Pacific; (G–I) BSKU 112578, 64.3 mm HL, 292+ mm TL, collected with BSKU 112572. (A, D, G) Lateral views; (B, E, H) dorsal and (C, F, I) ventral views of the head and trunk. [Photos: N. Nakayama]