Coelorinchus longissimus Matsubara, 1943 [Japanese name: Tongari-hige]

(Figs. 34C, 66; Appendix 3-4A)

Coelorhynchus longissimus Matsubara, 1943:140, figs. 1C, 2C, 5 (original description; holotype: FAKU 1592, from Kumanonada; new Japanese name: “Tongari-hige”); Matsubara 1955:1312, pl. 134, fig. 457 (in key; Japan); Kamohara 1958:73 (listed; Kochi Pref.); Chyung & Kim 1959:8, pl. II, figs. 16– 17 (first record from Korea; brief description; 1 spec. from Pusan, Korea); Okada et al. 1959:83 (listed; Kumano-nada); Kamohara 1964:95 (listed; Kochi Pref.); Matsubara 1965:506 (compiled; Japan); Okamura 1970a:165, pl. XXXV, text-fig. 67 (description; biological notes; 48 spec. from Pacific off southern Japan from Suruga Bay to Totoro); Kuroda 1971:56 [listed from Suruga Bay after Okamura (1970a)]; Kataoka & Tomida 1981:78 (listed; Mie Pref.); Tominaga & Uyeno 1981:488 (listed; Japan); Ohta 1983: table A (listed; Suruga Bay); Ozawa 1983:13 (listed; off Makurazaki, Kagoshima Pref., East China Sea).

Coelorhynchus (Quincuncia) longissimus: Okamura 1970b: table 1 (listed; Japan).

Coelorinchus longissimus: Yatou 1984:223, 366, fig. 159 [brief description; 9 spec. from Okinawa Trough; photo based on BSKU 39080 (from Mimase fish market); in part, BSKU 26581 is C. formosanus]; Okamura 1984b:96, pl. 82, fig. I (compiled); Okamura 1988:96, pl. 82, fig. I (compiled); Okamura 1997:126, fig. 9 (compiled); Youn 2002:538 (listed; Korea); Shao et al. 2008b: table 2 (3 spec. listed from northeastern and southwestern Taiwan); Nakabo & Kai 2013:506 (in key; Japan); Ikeda & Nakabo 2015:321, pl. 67, figs. 6–10 (brief description; spec. from Wakayama Pref.); Iwamoto et al. 2015:60 (brief description; 9 spec. from northeastern and southwestern Taiwan, and South China Sea); Motomura 2020:38 (listed; Japan).

Caelorinchus longissimus: Nakabo 1993:366 (in key; Japan); Shinohara & Matsuura 1997:291 (listed; Suruga Bay); Nakabo 2000:430 (in key; Japan); Shinohara et al. 2001:304 (listed; Tosa Bay); Nakabo 2002:430 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Chiou et al. 2004a:43, fig. 10 (brief description; 2 spec. from Daxi and Dong-gang; first record from Taiwan); Shinohara et al. 2005:416 (listed; Ryukyu Islands); Kim et al. 2005:172, fig. 293 (compiled; Korea; photo spec. represents C. multispinulosus); Kim et al. 2009a:13 (questionable; listed; Jeju Island, Korea); Furuhashi et al. 2010: table 2 (45 spec. listed from northern Okinawa Trough); Iwatsuki et al. 2017:32 (listed; Hyuga-nada).

Caelorinchus (Quincuncia) longissimus: Chiou et al. 2004a: table 1 (listed; Taiwan).

Diagnosis. Light organ tubular, completely covered with scales, externally represented by long black streak extending from immediately anterior to anus to chest just posterior to isthmus. Underside of head completely naked except for overlapping scales posterior to lateral nasal ridges (small scaly patches occasionally found on lower preopercles and posterior ends of mandibular rami); dorsal surface of snout broadly naked along each side of median rostral ridge. Snout long, sharply pointed, length 77–90% PRL, its dorsal profile concave in lateral view; terminal scute short, arrowhead-shaped, dorsoventrally flattened, length 12–22% PRL. Lateral nasal ridge incompletely supported by nasal bone. Anus abutting anal-fin origin. Premaxillary teeth small, slender, conical in moderately wide, long, tapered band, with outer series slightly enlarged; posterior margin of tooth band almost reaching lateral corner of mouth. Body scales covered with short, erect, needle-like spinules in subparallel to narrowly divergent rows; buttresses barely developed. Second dorsal fin distinctly lower than anal fin. Upperjaw length 42–49% PRL; preoral length 66–81% PRL; pectoral-fin length 55–64% PRL; height of first dorsal fin 58–70% PRL; interdorsal length 27–47% PRL; length of gill slit 20–25% PRL; barbel length 11–18% PRL. Body darker dorsally, silvery white ventrally; dark prominent blotches faint, often difficult to distinguish (prominently marked only in juveniles); median nasal bone blackish; underside of head generally pale, but mandibular rami blackish; no black hair-like papillae on naked areas on head; lips pale to dusky; oral cavity immaculate; gular and branchiostegal membranes heavily peppered with large melanophores; chest pale to dark; first dorsal fin dusky, but second spinous ray blackish; tip of pelvic fin prominently blackish.

Material examined. 29 specimens. Japan: BSKU 19077 (1, 73.0 mm HL, 256 mm TL), off Satsuma Peninsula, Okinawa Trough, 31.2267ºN, 129.9750ºE, 310 m, FRV Soyo-maru, sta. 72d, beam trawl, 12 Feb. 1959 ; BSKU 106767 (1, 68.2 mm HL, 240+ mm TL), southeast of Shimokoshiki-jima Island, East China Sea, 31.5658ºN, 129.8915ºE, 380 m, F/ V Maruko-maru, tr. 1, bottom trawl, coll. N. Nakayama et al., 24 Apr. 2012 ; BSKU 109052 (1, 48.7 mm HL, 185 mm TL), east of Kasayama Bank, 32.3884ºN, 129.0505ºE, 304–312 m, T/ V Nagasaki-maru, cr. N365, sta. A3, 3-m ORE beam trawl, coll. N. Nakayama, 19 Nov. 2012 ; BSKU 113743 (1, 86.1 mm HL, 313+ mm TL), off Katsurahama, Tosa Bay, 230 m, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama et al., 9 Apr. 2014 ; BSKU 99262 (1, 88.4 mm HL, 314+ mm TL), Mimase fish market, bottom trawl, 1 Mar. 2006; BSKU 40440 (1, 91.4 mm HL, 327+ mm TL), BSKU 40441 (1, 92.4 mm HL, 345+ mm TL), BSKU 40442 (1, 92.9 mm HL, 339 mm TL), BSKU 40445 (1, 96.2 mm HL, 342+ mm TL), BSKU 40447 (1, 92.6 mm HL, 341+ mm TL), BSKU 40448 (1, 95.9 mm HL, 277+ mm TL), BSKU 40451 (1, 96.6 mm HL, 338+ mm TL), BSKU 40457 (1, 81.0 mm HL, 304 mm TL), Mimase fish market, bottom trawl, 8 Mar. 1985; BSKU 99346 (1, 93.0 mm HL, 314+ mm TL), Mimase fish market, bottom trawl, coll. N. Nakayama, 23 Apr. 2008 ; BSKU 99235 (1, 81.5 mm HL, 303+ mm TL), BSKU 99237 (1, 58.9 mm HL, 219+ mm TL), Mimase fish market, bottom trawl, coll. N. Nakayama, 31 Oct. 2007 ; BSKU 55 (1, 76.4 mm HL, 302 mm TL), Mimase fish market, bottom trawl, coll. T. Kamohara, 5 Mar. 1951 ; BSKU 100497 (1, 78.7 mm HL, 287+ mm TL), Mimase fish market, F/ V Kosei-maru, bottom trawl, 15 Oct. 2009 ; BSKU 108871 (1, 77.5 mm HL, 278+ mm TL), Mimase fish market, F/ V Kosei-maru, bottom trawl, 22 Oct. 2012 ; BSKU 94450 (1, 71.6 mm HL, 251+ mm TL), Mimase fish market, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama, 14 Apr. 2008 ; BSKU 93088 (1, 63.4 mm HL, 237 mm TL), BSKU 93090 (1, 89.9 mm HL, 321+ mm TL), Mimase fish market, F/ V Seiryo-maru, bottom trawl, coll. N. Nakayama, 24 Dec. 2007 ; BSKU 94387 (1, 51.5 mm HL, 203+ mm TL), Mimase fish market, F/ V Seiryo-maru, bottom trawl, coll. N. Nakayama, 4 Apr. 2008 ; BSKU 69291 (1, 56.1 mm HL, 198+ mm TL), BSKU 69295 (1, 55.7 mm HL, 187+ mm TL), Tosa Bay, 33.1450ºN, 133.5150ºE, 240– 249 m, FRV Kotaka-maru, otter trawl, coll. H. Endo, 20 Aug. 1997 ; BSKU 112928 (1, 98.7 mm HL, 342+ mm TL), off Okitsu, Tosa Bay, 280–320 m, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama et al., 24 Jan. 2014 ; BSKU 110426 (1, 29.8 mm HL, 113+ mm TL), Suruga Bay, 34.7651ºN, 138.4880ºE, 200–450 m, F/ V Hinodemaru, sta. 4, bottom trawl, coll. N. Nakayama and R. Misawa, 23 Apr. 2013 ; BSKU 110081 (1, 40.7 mm HL, 154 mm TL), BSKU 110082 (1, 38.3 mm HL, 132+ 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 .

Counts and measurements. Based on 29 specimens (29.8–98.7 mm HL, 113+–345+ mm TL). Counts: first dorsal-fin rays II,9–10; pectoral-fin rays i15–i18; pelvicfin rays 7; gill rakers on first arch (outer/inner) 0/7–8, on second arch 5–6/7–9; longitudinal scales 36–45; transverse scale rows below first dorsal-fin origin 4.5–7, below first dorsal-fin midbase 3.5–5.5, below second dorsal-fin origin 3.5–5.5, above anal-fin origin 12–18.5.

The following measurements are in % of HL, followed by those in % of PRL in parentheses:snout length 44–48 (77–90); orbit diameter 23–29 (43–51); postorbital length 28–31 (51–58); postrostral length 53–57; orbitpreopercle distance 31–37 (57–68); suborbital width 10– 12 (19–22); upper-jaw length 23–27 (42–49); length of rictus 18–21 (32–38); length of premaxillary tooth band 15–18 (26–33); preoral length 38–45 (66–81); length of terminal snout scute 7–12 (12–22); length of lateral nasal ridge 30–35 (54–66); length of suborbital ridge 96– 101 (168–185); snout width 22–27 (39–48); internasal width 17–22 (32–41); interorbital width 21–24 (38–43); occipital width 6–8 (11–14); body width over pectoral-fin bases 28–44 (50–80); body depth at first dorsal-fin origin 37–54 (70–99); body depth at anal-fin origin 32–45 (56– 82); prepelvic length 101–115 (183–207); preanus length 130–152 (234–275); preanal length 133–155 (236–281); isthmus–pelvic distance 27–36 (50–65); isthmus–anus distance 55–71 (99–128); isthmus–anal distance 56–79 (103–143); pelvic–anal distance 31–47 (56–88); anusanal distance 1–4 (2–8); pelvic-fin length 20–32 (36–59); pectoral-fin length 30–34 (55–64); predorsal length 103– 109 (184–200); height of first dorsal fin 32–37 (58–70); length of first dorsal-fin base 15–19 (28–35); interdorsal length 15–26 (27–47); length of gill slit 11–14 (20–25); length of posterior nostril 6–9 (10–16); barbel length 6– 10 (11–18).

Size. To about 36 cm TL (Okamura 1970a).

Distribution. Known from Japan and Taiwan. Distributed in the Pacific off southern Japan northward to the Boso Peninsula (139.89ºE), Okinawa Trough, and northern South China Sea, at depths of 170–450 m (Chiou et al. 2004b; Shao et al. 2008a, 2008b; this study; Appendix 3-4A). Common.

Comments on holotype. Coelorinchus longissimus was described by Matsubara (1943) based on a single specimen collected from the Kumano-nada, Japan. Unfortunately, the holotype is considered lost during WWII (see the Comments on holotype of C. hige).

Remarks, relationships, and comparisons. Coelorinchus longissimus has been well described by previous authors, and thus does not need repeating here. The reader can refer to the original description (Matsubara 1943) and Okamura (1970a) for further morphological details.This species belongs to the C. argentatus group (see the Relationships of C. formosanus), and is most similar to C. gaesorhynchus Iwamoto & Williams, 1999 known from the eastern Indian Ocean off Western Australia. The two species are similar to each other in having the absence of prominent markings on the body, such as dark sports, blotches, stripes, or vermiculations (except for small specimens of C. longissimus). However, C. longissimus is readily distinguished from C. gaesorhynchus by having a shorter snout (77–90% PRL vs. 93–100%), preoral (66– 81% PRL vs. 85–92%), and terminal snout scute (12–22% PRL vs. 25–26%).

If some scales remain on the body dorsum, the species is unlikely to be confused with other Japanese species of the C. argentatus group, viz., C. formosanus Okamura, 1963, C. kamoharai Matsubara, 1943, and C. multispinulosus Katayama, 1942 . In C. longissimus, spinules on the body scales are arranged in subparallel to narrowly divergent rows (Fig. 34C), whereas those of the other three species are in quincunx order (Fig. 34 A–B, D). In addition, the blotched pattern of C. longissimus gradually becomes obscure with growth, but it is still discernable or prominently marked in adults of the other species (especially in preserved specimens). Coelorinchus longissimus is also distinguished from C. formosanus and C. multispinulosus in having a lower first dorsal fin (58– 70% PRL vs. Ż74%). It further differs from C. formosanus in lacking broad scaly patches on the ventral surfaces of the preopercle and the mandibular rami (vs. well developed), and in having a shorter barbel (11–18% PRL vs. 20–26%) and pectoral fin (55–64% PRL vs. 69–75%). Due to their close resemblance, C. longissimus may be confused with C. kamoharai in the field. However, C. longissimus lacks dark hair-like papillae on the underside of the head (vs. well developed in C. kamoharai). It is further separable from C. kamoharai in having a longer snout (snout length 77–90% PRL vs. 63–77%; preoral length 66–81% PRL vs. 51–65%), a shorter upper jaw (42–49% PRL vs. 47–54%), and a narrower gill slit (20–25% PRL vs. 26–29%).