Coryphaenoides longifilis Günther, 1877

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 179-184

Coryphaenoides longifilis Günther, 1877

[Japanese name: Himo-dara]

( Figs. 115–118 ; Appendix 3-6E)

Coryphaenoides longifilis G̹nther, 1877:439 [original description; holotype: BMNH 1887.12.7.136, from “south of Yeddo” (off Cape Omaezaki), Challenger sta. 235, in 565 ftm (1034 m)]; Okamura 1970a:121, pl. XXVI, text-fig. 50 (description; 6 spec. from Pacific off southern Japan from Kashima-nada to Mimase); Kuroda 1971:56 [listed from Suruga Bay after Okamura (1970a)]; Tominaga & Uyeno 1981:489 (listed; Japan); Shiogaki 1982:33 (listed; Aomori Pref.); Sawada 1983:109, 194, fig. 61 (brief description; 2 spec. from Pacific off Tohoku; photo based on HUMZ 78121); Ohta 1983: table B (listed; Suruga); Okamura 1984b:95, pl. 82, fig. B (compiled); Okamura 1988:95, pl. 82, fig. B (compiled); Nakabo 1993:362 (in key; Japan); Amaoka et al. 1995:103, fig. 153 (compiled; northern Japan); Hori 1996:28 (listed; Ibaraki Pref.); Shinohara et al. 1996:169 (2 spec. listed from Pacific off Tohoku); Shinohara & Matsuura 1997:291 (listed; Suruga Bay); Iwamoto 1990:211, fig. 488 (synopsis); Okamura 1997:125, fig. 5 (compiled); Funabashi 1998:85 (listed; Ibaraki Pref.); Nakabo 2000:426 (in key; Japan); Shinohara et al. 2001:305 (listed; Tosa Bay); Zama 2001:40 (listed; Miyagi Pref.); Nakabo 2002:426 (in key; Japan); Maeda & Tsutsui 2003:488 (listed; Hokkaido); Shiogaki et al. 2004:55 (listed; Pacific off Aomori Pref.); Senou et al. 2006:420 (listed; Sagami Sea); Senou 2008:366. fig. 31.33 (in situ observation; off Sanriku); Kitagawa et al. 2008:40, unnumbered fig. (brief description; spec. from Pacific off Tohoku); Shinohara et al. 2009:708 (1 spec. listed from Pacific off Tohoku); Amaoka et al. 2011:128, fig. 161 (compiled; Hokkaido); Nakabo & Kai 2013:502 (in key; Japan); Amaoka et al. 2020:160, fig. 215 (listed; Hokkaido); Motomura 2020:39 (listed; Japan).

Macrurus longifilis : G̹nther 1887:151, pl. XXXV (further description of holotype).

Bogoslovius clarki Jordan & Gilbert in Jordan & Evermann, 1898:2575 [original description; 4 syntypes in CAS and USNM; type locality: Bering Sea off Bogoslof Island, 54º51ʹ00ʺN, 167º27ʹ00ʺW, in 644 ftm (1178 m), Albatross sta. 3634; this publication predates Jordan & Gilbert (1899)]; Jordan & Gilbert 1899:487, pl. LXXXIII [description as a “new species”; preoccupied by Jordan & Gilbert in Jordan & Evermann (1898); 4 spec. from Albatross sta. 3634].

Dolloa longifilis : Jordan 1900:987 (new combination); Jordan & Gilbert in Jordan & Starks 1904:607 [after G̹nther (1877, 1887)]; Jordan et al. 1913:411 (listed; Japan; new Japanese name: “Himo-dara”); Kamohara 1931b:544 (questionable; listed; Kochi).

Moseleya longifilis : Jordan & Snyder 1901:119 (listed; Japan).

Nematonurus longifilis: Gilbert & Hubbs 1916:159 (new combination; description; 3 spec. from Hyuga-nada and Enshu-nada); Okada & Matsubara 1938:448 (in key; Japan); Kamohara 1950:276 (questionable; listed; Kochi Pref.); Kamohara 1952:96 (questionable; listed; Kochi Pref.); Matsubara 1955:1308 (in key; Japan); Kamohara 1958:73 (questionable; listed; Kochi Pref.); Kamohara 1964:95 (questionable; listed; Kochi Pref.); Tatara et al. 1965:121 (questionable; listed; off Shikoku).

Coryphaenoides (Nematonurus) longifilis: Taranetz 1937:169 (new combination; listed; Soviet Far East); Okamura 1970b: table 1 (listed; Japan).

Diagnosis. Pelvic-fin rays 9–10. Snout low, bluntly rounded in lateral view, protruding scarcely beyond large subterminal mouth. No modified scales on head ridges and tip and lateral angles of snout. Posterior margin of upper jaw extending to vertical through posterior 1/3 of orbit or beyond; upper-jaw length 40–46% HL; lateral corner of mouth not restricted by skin folds. Outermost gill slit moderately wide, length 14–23% HL. Barbel tiny, length 1–5% HL. Premaxillary teeth in 2 distinct rows with outer series notably enlarged; mandibular teeth in 2 irregular rows with inner series greatly enlarged. Body scales covered with short, reclined, needle-like to knife-like spinules in narrowly divergent rows (spinules rudimentary in larger specimens); tip of last spinule in each row scarcely extending beyond posterior scale margin (except in small specimens). Transverse scale rows below first dorsal-fin midbase 10–14.5. Head fully scaled except for narrow naked area on underside of snout. Interdorsal space less than first dorsal-fin base length. Height of first dorsal fin less than HL (71–94% HL); second spinous ray weakly serrated along its leading edge; first dorsal-fin rays II,12–15. Upper pectoral- and outer pelvic-fin rays greatly elongate, extending well beyond anal-fin origin. Body pale to blackish.

Material examined. 29 specimens. Holotype of Coryphaenoides longifilis: BMNH 1887.12.7.136 (113 mm HL, 667+ mm TL), off Cape Omaezaki, Enshunada, Japan , 34.1167ºN, 138.0000ºE, 565 ftm (1034 m), Challenger sta. 235, trawl, 4 Jun. 1875. Syntypes of Bogoslovius clarki: CAS-SU 5748 (2, 53.5–68.2 mm HL, 301+–389+ mm TL), north-northeast of Bogoslof Island , Bering Sea , 54.8500ºN, 167.4500ºW, 664 ftm (1215 m), Albatross sta. 3634, 7 Jul. 1896. Non-types : Japan: * BSKU 43477 (1, 130 mm HL, 767+ mm TL), off Miyazaki, Hyuga-nada , 32.0650ºN, 132.2950ºE, 1463–1514 m, R/V Tansei-maru, cr. KT-86-16, sta. E, 3- m beam trawl, 3 Nov. 1986; * BSKU 14194 (1, 68.0 mm HL, 367+ mm TL) , BSKU 14196 (1, 135 mm HL, 826+ mm TL) , off Hitachi , 36.3189ºN, 141.6667ºE, 1690 m, 3 Dec. 1967; HUMZ 72560 (1, 124 mm HL, 785+ mm TL) , off Fukushima, 37.1567ºN, 141.9333ºE, 900–920 m, F/V Hatsue-maru, No. 62, bottom trawl, coll. M. Toyoshima, 19 Jan. 1978; HUMZ 72597 (1, 135 mm HL, 860+ mm TL) , off Fukushima, 37.1833ºN, 141.9500ºE, 810–820 m, F/V Hatsue-maru, No. 62, bottom trawl, coll. M. Toyoshima, 18 Jan. 1978; HUMZ 72659 (1, 124 mm HL, 772 mm TL) , off Miyagi, 38.0333ºN, 142.4833ºE, 1100–1150 m, F/V Hatsue-maru, No. 62, bottom trawl, coll. M. Toyoshima, 7 Feb. 1978; HUMZ 72674 (1, 124 mm HL, 749+ mm TL), HUMZ 72675 (1, 118 mm HL, 535+ mm TL) , off Miyagi, 38.7250ºN, 142.3917ºE, 1000– 1100 m, F/V Hatsue-maru, No. 62, bottom trawl, coll. M. Toyoshima, 4 Feb. 1978; NSMT-P 104608 (1, 122 mm HL, 728+ mm TL), off Otsuchi, R /V Tansei-maru, cr. KT-87-05, sta. SR35, 3-m ORE beam trawl, 21 May 1985; HUMZ 78121 (1, 137 mm HL, 803 mm TL) , off Iwate, 39.1217ºN, 142.7750ºE , 1480–1485 m, bottom trawl, coll. K. Sakamoto, 20 Sept. 1978; NSMT-P 79350 (1, 89.9 mm HL, 500+ mm TL), off Kesennuma , 38.5367ºN, 142.8000ºE , 1502 m, FRV Wakataka-maru, sta. E-1500, bottom trawl, coll. Y. Takata, 26 Oct. 2007; BSKU 35689 (1, 88.7 mm HL, 497+ mm TL) , BSKU 35690 (1, 98.1 mm HL, 597+ mm TL) , BSKU 35692 (1, 102 mm HL, 584+ mm TL) , BSKU 35694 (1, 115 mm HL, 683+ mm TL) , off Kinkazan , 38.7333ºN, 143.1850ºE, 1950–1960 m, R/V Hakuho-maru, cr. KH-81-4, sta. 8, 25 Jul. 1981; BSKU 97807 (1, 129 mm HL, 777+ mm TL) , off Kuji , 40.3727ºN, 143.3827ºE , 1923–1995 m, R/ V Tansei-maru, cr. KT-93-15, sta. M5, 3-m beam trawl, coll. Y. Machida, 18 Nov. 1993; *NSMT-P 102089 (2, 21.8–44.7 mm HL, 96+–226+ mm TL), east-southeast of Oshika Peninsula , 38.0367ºN, 142.2250ºE , 829–831 m, FRV Wakatakamaru, otter trawl, coll. T. Fujita, 19 May 1995; NSMT-P 90551 (1, 78.0 mm HL, 457+ mm TL), off Kushiro , 1500 m, R/V Tansei-maru, cr. KT-07-29, coll. G. Shinohara, 7 Nov. 2007; * BSKU 114807 (1, 27.0 mm HL, 119+ mm TL) , south of Kushiro , 42.6542ºN, 144.3770ºE, 780 m, FRV Wakataka-maru, sta. D-700, otter trawl, coll. R. Misawa, 7 Jun. 2014; * BSKU 49902 (1, 96.2 mm HL, 522+ mm TL) , NSMT-P 105269 (1, ex. BSKU 49909, 115 mm HL, 682+ mm TL), NSMT-P 105270 (1, ex. BSKU 49906, 128 mm HL, 770+ mm TL), Japan, 1500 m, R/ V Hakuho-maru, cr. KH-91-06, sta. 12, 16 Nov. 1991 . Emperor Seamounts : HUMZ 71903 (1, 126 mm HL, 690+ mm TL), HUMZ 71905 (1, 140 mm HL, 824+ mm TL), Ojin Seamount, 38.0000ºN, 170.3000ºE, 920–1080 m, coll. Japan Marine Fishery Resources Research Center ( JAMARC), 17 Jul. 1977 ; HUMZ 88055 (1, 126 mm HL, 649+ mm TL), north of Nintoku Seamount , 42.2833ºN, 170.4200ºE, 1085–1200 m, F/ V Hokusei-maru, hook and line, coll. K. Nakaya, 23 Jul. 1980 .

Counts and measurements. Based on 23 specimens (53.5–140 mm HL, 301+–860+ mm TL). Counts: first dorsal-fin rays II,12–15; pectoral-fin rays i15–i19; pelvic-fin rays 9–10; gill rakers on first arch (outer/inner) 6–9/13–16, on second arch 12–15/13–15; longitudinal scales 38–52; transverse scale rows below first dorsalfin origin 13–17, below first dorsal-fin midbase 10–14.5, below second dorsal-fin origin 11–16.5, above anal-fin origin 48.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 24–28 (30–37); orbit diameter 19–25 (25–32); postorbital length 53–58 (69–75); postrostral length 74–79; orbit–preopercle distance 38–44 (48–58); suborbital width 9–13 (12–17); upper-jaw length 40–46 (52–62); length of rictus 35–40 (46–53); length of premaxillary tooth band 28–35 (36– 46); preoral length 4–7 (6–9); distance between tip and lateral angle of snout 8–11 (11–14); snout width 14–19 (18–24); internasal width 16–18 (21–24); interorbital width 22–26 (29–35); occipital width 2–8 (3–11); body width over pectoral-fin bases 30–56 (38–73); body depth at first dorsal-fin origin 70–86 (88–114); body depth at anal-fin origin 54–89 (71–118); prepelvic length 103–120 (132–159); preanus length 146–179 (191–237); preanal length 137–188 (174–249); isthmus–pelvic distance 42– 54 (55–72); isthmus–anus distance 87–115 (114–153); isthmus–anal distance 90–124 (116–164); pelvic–anal distance 43–74 (55–98); anus–anal distance 3–9 (4–12); pelvic-fin length 114–222 (151–291); pectoral-fin length 66–123 (84–162); predorsal length 104–116 (134–152); height of first dorsal fin 71–94 (90–120); length of first dorsal-fin base 31–42 (40–55); interdorsal length 10– 22 (12–27); length of gill slit 14–23 (19–29); length of posterior nostril 4–8 (5–10); barbel length 1–5 (1–6).

Size. Attains about 97 cm TL ( NSMT-P 102193, 973+ mm TL, off Kesennuma, Japan).

Variation. Spinulation on the body scales is well developed in young specimens, and it tends to become weaker with increasing body size ( Fig. 118 ). In adults, the spinulation is usually rudimentary and difficult to distinguish ( Fig. 118 B–C, F–G), but some specimens have prominent spinules so as to give a spiny appearance to body surfaces ( Fig. 118D, H ).

Distribution. Distributed in Japan and the Bering Sea, as well as on the Emperor Seamounts, at depths of 700– 2025 m ( Iwamoto & Stein 1974; Borets 1986; Iwamoto 1990; Mecklenburg et al. 2002; this study). In Japanese waters, known from off the Pacific coasts southward to Miyazaki (31.90ºN) and the Shichito-Iojima Ridge at depths of 780‾ 2000 m (Appendix 3-6E). Moderately common in northern Japan, but rare in the west of the Boso Peninsula (139.89ºE) and at the Shichito-Iojima Ridge.

Remarks. For a full description see Okamura (1970a) and Iwamoto & Stein (1994). Coryphaenoides longifilis was originally described by G̹nther (1877) based on a single specimen ( Fig. 116 ) collected during the “ Challenger ” Expedition from the Enshu-nada off Cape Omaezaki, Japan, at a depth of 1034 m (Challenger sta. 235). Subsequently, Jordan & Gilbert (in Jordan & Evermann 1898) described Bogoslovius clarki as a new species based on four specimens collected from the Bering Sea off Bogoslof Island at a depth of 1214 m ( Fig. 117 ). However, Makushok (1964) synonymized this species with C. longifilis based on a detailed comparison of literature data.

Relationships. The subgeneric affiliation of this enigmatic species needs further discussion. Although it was originally included in the genus Coryphaenoides , G̹nther (1887) subsequently classified the species under the subgenus Nematonurus G̹nther, 1887 of the genus Macrurus (= Macrourus Bloch, 1786 ). Goode & Bean (1896) established Moseleya as a monotypic genus for C. longifilis , but the name is preoccupied by the stony coral genus Moseleya Quelch, 1884 (Cnidaria: Scleractinia : Lobophylliidae ). Jordan (1900) subsequently provided a replacement name, Dolloa , for Goode & Bean’s (1896) Moseleya . However, Gilbert & Hubbs (1916) regarded Dolloa as a junior synonym of Nematonurus , to which they gave full generic status. Okamura (1970a) and Iwamoto & Stein (1974) classified the species under Coryphaenoides , and relegated Nematonurus to subgeneric rank. Iwamoto & Sazonov (1988) listed C. longifilis under the subgenus Coryphaenoides , but Iwamoto (1990) transferred the species to the subgenus Bogoslovius Jordan & Evermann, 1898.

According to a molecular phylogeny based on the 12S mitochondrial ribosomal gene from 12 Coryphaenoides species ( Wilson & Attia 2003: fig. 2), C. longifilis belongs to the subgenus Coryphaenoides , and is sister to a clade that comprises C. acrolepis ( Bean, 1884) , C. cinereus ( Gilbert, 1896) , C. filifer ( Gilbert, 1896) , and C. pectoralis ( Gilbert, 1891) . However, it is evident that more investigations are necessary for a better understanding of the subgeneric classification of Coryphaenoides . Considering that the genus represents the second largest group of the family, a more comprehensive analysis with broader taxon sampling is required to make a definitive conclusion on the species’ phylogenetic position. This study follows Iwamoto’s (1990) classification, and C. longifilis is considered to belong the subgenus Bogoslovius , of which the species is the only representative.

Comparisons. Coryphaenoides longifilis is unlikely to be confused with other congeners in its diagnostic dentition: the dentary teeth are arranged in two distinct series, with those of the inner row modified into enlarged canines. In addition, C. longifilis is easily recognized due to its unique physiognomy: unlike most other species of the genus, the snout of C. longifilis is broadly rounded and barely protrudes beyond the upper jaw; this feature is shared only with C. gypsochilus Iwamoto & McCosker, 2001 known from the Galápagos Islands and some species of the subgenus Fuyangia Whitley, 1931 (see also the Relationships of C. leptolepis ). Coryphaenoides longifilis is one of the few species of the genus in which the outer pelvic-fin ray is extremely prolonged (its length greater than 1.5 times HL).Among the species of Coryphaenoides , the first dorsal fin is best developed in C. longifilis , and its base length appears to be the longest (31–42% HL); higher counts of first dorsal-fin rays (II,12–15) also diagnose the species. Furthermore, body scales are much smaller in C. longifilis (below first dorsal-fin midbase 10–14.5; below second dorsal-fin origin 11–16.5) than in any other congeners.

Figures

FIGURE 115. Fresh specimens of Coryphaenoides longifilis. (A) BSKU 114807, 27.0 mm HL, 119+ mm TL, south of Kushiro, Hokkaido, Pacific; (B) BSKU 49902, 96.2 mm HL, 522+ mm TL, KH-91-6, sta. 12, 1500 m depth; (C) HUMZ 88055, 126 mm HL, 649+ mm TL, Emperor Seamounts; (D) BSKU 43477, 130 mm HL, 767+ mm TL, Hyuga-nada off Miyazaki Pref., Pacific, 1514–1463 m depth. Lateral views. [Photos: (A) N. Nakayama; (B, D) BSKU; (C) HUMZ]

FIGURE 116. Holotype of Coryphaenoides longifilis. BMNH 1887.12.7.136, 113 mm HL, 667+ mm TL, off Cape Omaezaki, Enshu-nada, Pacific, 1034 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]

FIGURE 117. Preserved specimen of Coryphaenoides longifilis. CAS-SU 5748, syntype of Bogoslovius clarki (1 of 2 spec.), 68.2 mm HL, 389+ mm TL, north-northeast of Bogoslof Island, Bering Sea, 1215 m depth. (A) Lateral, (B) dorsal, and (C) ventral views. Preserved condition. [Photos: N. Nakayama]

FIGURE118. Scanningelectron micrographsshowingbodyscales (from thedorsum belowthe interdorsalspace) ofCoryphaenoides longifilis. (A, E) NSMT-P 102089, 44.7 mm HL; (B, F) BSKU 14194, 68.0 mm HL; (C, G) NSMT-P 104608, 122 mm HL; (D, H) BSKU 97807, 129 mm HL. (A–D) Views from above; (E–H) oblique views. [Photos: NSMT]