Coelorinchus formosanus Okamura, 1963

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 48-50

Coelorinchus formosanus Okamura, 1963

[Japanese name: Taiwan-sokodara]

( Figs. 32–33 , 34A ; Appendix 3-2A)

Coelorhynchus formosanus Okamura, 1963b:37 , figs. 1–2 [original description; holotype: FAKU 35836, from “Tashi” (Daxi); 4 paratypes from Taiwan]; Okamura 1970a:161, pl. XXXIV, text-figs. 65–66 (description; re-examination of type specimens; new Japanese name: “Taiwan-sokodara”); Tominaga & Uyeno 1981:488 (listed; Japan).

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

Coelorinchus longissimus (not Matsubara 1943): Yatou 1984:223, 366, fig. 159 (brief description; Okinawa Trough; in part, BSKU 26581).

Coelorinchus formosanus : Okamura 1984b:96, pl. 82, fig. J (compiled); Okamura 1988:96, pl. 82, fig. J (compiled); Iwamoto 1990:158, fig. 372 (synopsis); Shao et al. 2008b: table 2 (9 spec. listed from northeastern and southwestern Taiwan, and South China Sea); Kim et al. 2009b:112, fig. 6 (brief description; 2 spec. from Korea; new Korean record); Ho & Shao 2011:36 (type catalog); Nakabo & Kai 2013:506 (in key; Japan); Iwamoto et al. 2015:54 (brief description; 38 spec. from northeastern Taiwan); Motomura 2020:38 (listed; Japan).

Caelorinchus formosanus : Nakabo 1993:366 (in key; Japan); Shao 1993:168 (compiled; Taiwan); Nakabo 2000:430 (in key; Japan); Nakabo 2002:430 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Shinohara et al. 2005:416 (listed; Ryukyu Islands).

Caelorinchus (Quincuncia) formosanus : 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 snout completely naked except for overlapping scales along lateral nasal ridges; underside of head posterior to level of midorbit heavily scaled, but anterior portions of mandibular rami mostly naked; top of snout broadly naked along each side of median rostral ridge. Snout long, sharply pointed, length 66–84% PRL, its dorsal profile slightly concave in lateral view; terminal scute short, arrowhead-shaped, dorsoventrally flattened, length 7–18% 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, spike-like, trihedral spinules in irregularly quincunx order to widely divergent rows; buttresses well developed. Second dorsal fin distinctly lower than anal fin. Upper-jaw length 45–51% PRL; pectoral-fin length 69–75% PRL; height of first dorsal fin 74–85% PRL; interdorsal length 35–50% PRL; length of gill slit 21–26% PRL; barbel length 20–26% PRL. Dorsal half of body with faint, dark, irregular blotches; lower half of head and body silvery white when viewed laterally; median nasal bone blackish; underside of head generally pale; black hair-like papillae scarcely developed on naked areas on head; lips dusky; oral cavity pale; gular and branchiostegal membranes heavily peppered with large melanophores; chest dark; first dorsal fin dusky, but second spinous ray prominently blackish; pelvic fin darker distally.

Material examined. 23 specimens. Holotype of Coelorhynchus formosanus: FAKU 35856 (72.8 mm HL, 221+ mm TL), Da-xi fish market, Yilan, northwestern Taiwan , bottom trawl, 6 Dec. 1961 . Paratypes of C. formosanus: FAKU 35859 (1, 62.3 mm HL, 238+ mm TL), FAKU 35860 (1, 57.8 mm HL, 212+ mm TL), Daxi fish market, Yilan, bottom trawl, 1958–1961 ; * FAKU 35857 (1, 46.7 mm HL, 167+ mm TL) , * FAKU 35858 (1, 55.4 mm HL, 195+ mm TL), Kaoshiung, South China Sea , bottom trawl, 1958–1961. Non-types: Japan : BSKU 159 (1, 69.0 mm HL, 272+ mm TL), Mimase fish market, bottom trawl, 21 Mar. 1951 . Taiwan: BSKU 108963 (1, 79.9 mm HL, 318+ mm TL), Da-xi fish market, Yilan, 25 Jul. 2012 ; BSKU 98972 (1, 57.9 mm HL, 216+ mm TL), Da-xi fish market, Yilan, coll. H.-C. Ho, 8 Nov. 2007 ; BSKU 50363 (1, 51.3 mm HL, 215 mm TL) , BSKU 50466 (1, 37.6 mm HL, 128+ mm TL) , BSKU 50468 (1, 53.2 mm HL, 189+ mm TL) , BSKU 50469 (1, 38.9 mm HL, 152+ mm TL) , BSKU 50471 (1, 51.8 mm HL, 210+ mm TL) , BSKU 50472 (1, 54.3 mm HL, 200+ mm TL) , BSKU 50473 (1, 59.2 mm HL, 214+ mm TL) , BSKU 50474 (1, 57.4 mm HL, 217+ mm TL) , BSKU 50488 (1, 38.6 mm HL, 158 mm TL), Da-xi fish market, Yilan, coll. T. Yamakawa and R.Asaoka, 23Apr. 2012 ; * BSKU 99863 (1, ca. 72 mm HL, 302 mm TL) , BSKU 99866 (1, 66.1 mm HL, 216+ mm TL), Da-xi fish market, Yilan, coll. M.-Y. Lee, 30 Jun. 2009 ; KAUM-I. 44655 (1, 69.7 mm HL, 204+ mm TL), off Kaohsiung, Yilan, 400 m, trawl, coll. M. Matsunuma and H.-C. Ho, 1 Jul. 2011 ; BSKU 29993 (1, 52.5 mm HL, 184+ mm TL) , BSKU 29994 (1, 40.7 mm HL, 155+ mm TL), Dong-gang , Pingtung, otter trawl, coll. T. Kanayama, 6–7 Dec. 1978 ; * FAKU 204426 (1, 367+ mm TL), Dong-gang fish market, Pingtung, bottom trawl, coll. N. Nakayama, 27 Feb. 2017 .

Counts and measurements. Based on 19 specimens (37.6–79.9 mm HL, 128+–318+ mm TL). Counts: first dorsal-fin rays II,8–10; pectoral-fin rays i15–i17; pelvicfin rays 7; gill rakers on first arch (outer/inner) 0/7–9, on second arch 6–7/8–9; longitudinal scales 36–45; transverse scale rows below first dorsal-fin origin 4.5– 6.5, below first dorsal-fin midbase 3.5–5, below second dorsal-fin origin 3.5–5, above anal-fin origin 11.5–14.5.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 40–46 (66–84); orbit diameter 23–27 (41–47); postorbital length 30–36 (54–59); postrostral length 54– 61; orbit–preopercle distance 33–37 (58–66); suborbital width 10–12 (17–20); upper-jaw length 25–30 (45–51); length of rictus 20–24 (36–43); length of premaxillary tooth band 17–22 (30–36); preoral length 33–39 (55–72); length of terminal snout scute 4–10 (7–18); length of lateral nasal ridge 26–34 (43–61); length of suborbital ridge 93–99 (157–180); snout width 22–25 (38–45); internasal width 18–21 (31–38); interorbital width 21–24 (37–43); occipital width 6–9 (10–15); body width over pectoral-fin bases 32–44 (58–81); body depth at first dorsal-fin origin 47–57 (82–104); body depth at anal-fin origin 41–47 (70–86); prepelvic length 100–109 (171– 195); preanus length 141–152 (249–270); preanal length 144–156 (256–273); isthmus–pelvic distance 30–39 (53– 70); isthmus–anus distance 71–83 (126–146); isthmusanal distance 73–87 (130–153); pelvic–anal distance 40–54 (72–94); anus–anal distance 2–4 (4–7); pelvic-fin length 26–35 (47–61); pectoral-fin length 38–44 (69–75); predorsal length 102–110 (178–200); height of first dorsal fin 41–47 (74–85); length of first dorsal-fin base 17–20 (29–36); interdorsal length 20–28 (35–50); length of gill slit 12–14 (21–26); length of posterior nostril 6–8 (9–14); barbel length 11–15 (20–26).

Size. To about 32 cm TL ( BSKU 108963, 318+ mm TL, Da-xi, northern Taiwan).

Distribution. Restricted to the northwestern Pacific off Taiwan, Japan, and Korea. Known from the northern South China Sea, Okinawa Trough, Tosa Bay, and Sea of Japan off the Korean Peninsula (Chu & Lo in Chu et al. 1963; Shao et al. 2008a, 2008b; Kim et al. 2009b; this study; Appendix 3-2A). Depth range 158–400 m, plus a single capture in 985–1110 m (ASIZP 65595; Iwamoto et al. 2015). One of the most common grenadiers found in fish markets in Taiwan, but rare in Japanese waters.

Remarks. Coelorinchus formosanus was described by Okamura (1963b) based on five specimens collected from northeastern Taiwan ( Fig. 33 ). The original description is excellent and can be referred to for details. In the same year, Chu & Lo (in Chu et al. 1963) described C. abbreviatus and C. intermedius from the northern part of the East China Sea. Although Okamura (1970a) subsequently regarded these species synonymous, C. abbreviatus and C. intermedius are considered as junior synonyms of C. multispinulosus Katayama, 1942 in this study (see the Nomenclatural discussion of C. multispinulosus ).

Relationships. Coelorinchus formosanus belongs to the C. argentatus group as defined by Nakayama et al. (2020), which includes the following 13 species: C. argentatus Smith & Radcliffe in Radcliffe, 1912 from the Philippines, New Caledonia and northern Australia; C. denticulatus Regan, 1921 from the western Indian Ocean; C. formosanus ; C. gaesorhynchus Iwamoto & Williams, 1999 from Western Australia; C. kamoharai Matsubara, 1943 and C. longissimus Matsubara, 1943 from Japan to Taiwan; C. mayiae Iwamoto & Williams, 1999 from the Arafura Sea; C. multispinulosus from Japan to Vietnam; C. pardus Iwamoto & Williams, 1999 from the Arafura Sea; C. posteromaculatus Nakayama, Prokofiev & Kawai, 2020 from the eastern Indian Ocean; C. quincunciatus Gilbert & Hubbs, 1920 from the Philippines; C. semaphoreus Iwamoto & Merrett, 1997 from New Caledonia and Queensland, Australia; and C. thompsoni Gilbert & Hubbs, 1920 from the Philippines. These species are distinguished from other congeners by having the following combination of features ( Nakayama et al. 2020): light organ long, extending from anus to chest just posterior to isthmus; no interspace between anus and anal-fin origin; lateral nasal ridge incompletely supported by nasal bone; premaxillary teeth in long tapered band, with posterior margin of tooth band almost reaching lateral corner of mouth; body scales covered with short, erect spinules in quincunx order or subparallel to slightly divergent rows; modified scales on head ridges not prominently spinulated; dorsal surfaces of snout broadly naked along each side of median rostral ridge; second dorsal fin poorly developed, its height distinctly lower than that of anal fin; dark prominent markings, such as spots, blotches, stripes, and vermiculations, usually present dorsally on trunk and tail; lower half of body overlain with silvery reflections (often indistinct in preserved specimens). The above definition generally agrees with the original concept of the subgenus Quincuncia Gilbert & Hubbs, 1920 that initially comprised C. argentatus (type species), C. quincunciatus and C. thompsoni (see Nakayama et al. 2020).

McCann & McKnight (1980) described C. campbellicus from the southeast of New Zealand, classifying the species under Quincuncia . This species is excluded from the C. argentatus group, because of its short light organ [43% HL (fide McCann & McKnight 1980:57) vs. about 70% in species of the C. argentatus group]. McCann & McKnight (1980:57) also described C. campbellicus as having “anterior photophore covered by scales, posterior ovoid, naked”, but the light organ of the C. argentatus group is completely covered with sales. The species seems to be closely related to C. kaiyomaru Arai & Iwamoto, 1979 , widely distributed in temperate waters in the Southern Hemisphere.

Comparisons. Coelorinchus formosanus is distinctive among the C. argentatus group in that the underside of the head is heavily scaled posteriorly, but almost completely naked anteriorly (vs. either almost entirely scaled or naked). It further differs from all except large specimens of C. argentatus in having body scales covered with short, spike-like, trihedral spinules with welldeveloped buttresses ( Fig. 34A vs. spinules needle-like or triangular, and buttresses poorly developed, Fig. 34 B–D).

In Japanese waters, C. formosanus might be confused with C. longissimus due to their similar appearance and coloration. In addition to the above-mentioned features, C. formosanus is readily distinguished from C. longissimus by having a longer barbel (20–26% PRL vs. 11–18%) and pectoral fin (69–75% PRL vs. 55–64%), higher first dorsal fin (74–85% PRL vs. 58–70%), and body-scale spinules arranged in more or less quincunx order (vs. subparallel narrowly divergent rows). Large individuals of C. longissimus occasionally have rudimentary scaly patch(es) on the ventral surfaces of the preopercles, but the mandibular rami are always naked, except the posterior margins where a few scales are rarely present (vs. usually heavily scaled in C. formosanus ).

Figures

FIGURE 32. Fresh specimen of Coelorinchus formosanus. FAKU 204426, 367+ mm TL, Dong-gang fish market, southwestern Taiwan, South China Sea. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. [Photos: N. Nakayama]

FIGURE 33. Holotype of Coelorhynchus formosanus (= Coelorinchus formosanus). FAKU 35856, 72.8 mm HL, 221+ mm TL, Da-xi fish market, northeastern Taiwan, East China Sea. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]

FIGURE 34. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of four species of the Coelorinchus argentatus group. (A) C. formosanus, BSKU 99863, ca. 72 mm HL; (B) C. kamoharai, BSKU 93575, 59.6 mm HL; (C) C. longissimus, BSKU 40448, 95.9 mm HL; (D) C. multispinulosus, BSKU 99273, 69.9 mm HL. Views from above. [Photos: N. Nakayama]