Coryphaenoides armatus ( Hector, 1875 )

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 150-152

Coryphaenoides armatus ( Hector, 1875)

[Japanese name: Yoroidara]

( Figs. 97–98 , 99A , 100 A–B; Appendix 3-5F)

Macrurus armatus Hector, 1875:81 [original description; holotype: BMNH 1982.6 .8.1, from ca. 200 miles west of Cape Farewell , New Zealand, in 400 ftm (732 m)].

Coryphaenoides variabilis G̹nther, 1878:27 [original description; lectotype: BMNH 1889.12 .7.130, from Mid-Pacific, Challenger sta. 246, in 2050 ftm (3749 m); paralectotypes from sta. 146, 157, 246, 271, and 300; in part, see the Comments on type specimens of C. leptolepis ; lectotype designated by Wilson & Waples (1983:1136)] .

Macrurus asper Goode & Bean, 1883:196 [original description; 6 syntypes (MCZ and USNM), from northwestern Atlantic , Blake sta. 308 and 309, in 304–1242 ftm (556–2271 m)].

Macrurus goodii G̹nther, 1887:136 [original description based on type specimens of M. asper Goode & Bean, 1833 ; replacement name for the latter species preoccupied by C. asper G̹nther, 1877).

Coryphaenoides gigas Vaillant, 1888:232 , pl. XX, figs. 2, 2a, 2b, 2c [original description; lectotype: MNHN 1886-0117, from northeastern Atlantic, in 4255 m; 1 paralectotype from northeastern Atlantic; lectotype designated by Eschmeyer (1998:645)].

Nematonurus cyclolepis Gilbert, 1896:458 [original description; 2 syntypes (CAS-SU and USNM), from off Queen Charlotte Island, British Columbia, northeastern Pacific, Albatross sta. 3342, in 1588 ftm (2904 m)].

Macrurus (Nematonurus) suborbitalis Gill & Townsend, 1897:234 [original description; holotype: USNM 48773 , from southwest of Pribilof Islands , Bering Sea, Albatross sta. 3603, 1771 ftm (3129 m)].

Nematonurus abyssorum Gilbert, 1915:374 , pl. 21, fig. 23 [original description; holotype: USNM 75827 , from off Santa Catalina Island , northeastern Pacific, Albatross sta. 4390, in 1350– 2182 ftm (2469–3990 m)].

Coryphaenoides armatus: Iwamoto 1990:205 , fig. 478 (synopsis); Endo & Okamura 1992:433, fig. 1 (first record from Japan; brief description; 5 spec. from northwestern Pacific; new Japanese name: “Yoroidara”); Nakabo 1993:363 (in key; Japan); Okamura 1997:125, fig. 6 (compiled); Endo et al. 2000:16, photo C (in situ observation; Nankai Trough); Nakabo 2000:427 (in key; Japan); Nakabo 2002:427 (in key; Japan); Shinohara et al. 2009:708 (listed; Pacific off Tohoku); Nakabo & Kai 2013:503 (in key; Japan); Amaoka et al. 2020:161, fig. 217 (listed; Hokkaido); Motomura 2020:39 (listed; Japan).

[?] Coryphaenoides sp.: Senou 2008:367, fig. 31.36 (in situ observation; Chishima Trench).

Diagnosis. Pelvic-fin rays 9–12 (usually 11). Snout rounded in adults (conical in young specimens), slightly protruding beyond upper jaw. Tip and lateral angles of snout armed with small scute-like scales; scales along head ridges slightly thickened but not especially enlarged. Mouth large, posterior margin of upper jaw extending to about vertical through hind rim of orbit; upper-jaw length 35–41% HL; lateral corner of mouth not restricted by skin folds. Outermost gill slit moderately wide, length 15–20% HL. Barbel long, stout at base, length 13–20% HL. Teeth slender, bluntly pointed; premaxillary teeth in 2 distinct rows, with outer series enlarged (inner row usually absent in larger specimens); mandibular teeth in uniserial row. Body scales covered with short, reclined, needle-like to knife-like spinules in subparallel to slightly divergent rows; tip of last spinule in each row extending to posterior scale margin or slightly beyond. Transverse scale rows below first dorsal-fin midbase 6–8.Top of snout narrowly naked posterior to leading edges; underside of head mostly naked, with narrow scaly patches below infraorbital ridges and on posterior parts of mandibular rami. Interdorsal space greater than first dorsal-fin base length. Height of first dorsal fin less than HL (64–90% HL); second spinous ray not prolonged, weakly serrated along its leading edge; first dorsal-fin rays II,9–10. Body uniformly dark brown.

Material examined. 18 specimens. Japan : BSKU 96414 (1, 44.5 mm HL, 249 mm TL), southeast of Cape Erimomisaki , Japan Trench, 41.2005ºN, 143.9330ºE, 2889–2995 m, R/ V Tansei-maru, cr. KT-08-27, sta. S-4, 3-m ORE beam trawl, coll. H. Endo and N. Nakayama, 21 Oct. 2008 ; BSKU 96459 (1, 48.8 mm HL, 242+ mm TL), off Miyako , 39.5342ºN, 143.6835ºE, 3150–3201 m, R/ V Tansei-maru, cr. KT-08-27, sta. M-4, 3-m ORE beam trawl, coll. H. Endo and N. Nakayama, 22 Oct. 2008 ; BSKU 96478 (1, 37.1 mm HL, 202+ mm TL), off Kinkazan , 38.4748ºN, 143.3470ºE, 2698–2814 m, R/ V Tansei-maru, cr. KT-08-27, sta. K-3, 3-m ORE beam trawl, coll. H. Endo and N. Nakayama, 23 Oct. 2008 ; NSMT-P 30199 (1, 92.1 mm HL, 527+ mm TL), east of Tori-shima Island , western Pacific, 30.1687ºN, 146.8190ºE, 6273 m, R/V Tokyo-daigaku-maru, fish trap, 11 Oct. 1985 ; NSMT-P 97647 (1, 146 mm HL, 848+ mm TL), NSMT-P 97648 (1, 150 mm HL, 805+ mm TL), NSMT-P 97649 (1, 158 mm HL, 902+ mm TL), NSMT-P 97651 (1, 89.7 mm HL, 515 mm TL), NSMT-P 97669 (1, 103 mm HL, 576+ mm TL), NSMT-P 98008 (1, 110 mm HL, 587+ mm TL), off Miyako , 38.7983ºN, 144.1345ºE, 7340–7433 m, R/ V Hakuho-maru, cr. KH-01-02, sta. TD-7, 30 Sept. 2001 ; BSKU 35722 (1, 91.7 mm HL, 542+ mm TL) , BSKU 35723 (1, 103 mm HL, 626+ mm TL), off Kuji , Japan Trench, 40.1133ºN, 143.9700ºE, 4200–4220 m, R/ V Hakuho-maru, cr. KH-84-1, sta. 7-1, 15 Jul. 1981 ; BSKU 37297 (1, 141 mm HL, 753+ mm TL) , BSKU 37299 (1, 107 mm HL, 642+ mm TL), east of Choshi , Japan Trench, 35.8367ºN, 142.2083ºE, 4100 m, T/ V Bosei-maru, fish trap, 4 Nov. 1981 ; NSMT-P 30197 (1, 144 mm HL, 664 mm TL), NSMT-P 30200 (1, 118 mm HL, 633+ mm TL), east of Cape Inbozaki , 35.8333ºN, 142.2000ºE, 4100 m, T/ V Bosei-maru, fish trap, 2 Nov. 1981 . Northeastern Pacific : BSKU 44504 (1, 99.2 mm HL, 524+ mm TL), off New Port , 44.9500ºN, 126.6167ºW, 2850 m, 19 Feb. 1971 ; BSKU 44505 (1, 89.7 mm HL, 469+ mm TL), 2700 m, Feb. 1971 .

Counts and measurements. Based on 18 specimens (37.1–158 mm HL, 202+–902+ mm TL). Counts: first dorsal-fin rays II,9–10; pectoral-fin rays i17–i21; pelvicfin rays 9–12; gill rakers on first arch (outer/inner) 7–10/12–15, on second arch 11–14/11–14; longitudinal scales 29–44; transverse scale rows below first dorsal-fin origin 7.5–13, below first dorsal-fin midbase 6–8, below second dorsal-fin origin 7.5–10, above anal-fin origin 25.5–35.5; pyloric caeca 11.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 23–29 (28–39); orbit diameter 18–25 (24–33); postorbital length 51–61 (67–77); postrostral length 74– 81; orbit–preopercle distance 44–49 (57–63); suborbital width 9–13 (12–18); upper-jaw length 35–41 (46–55); length of rictus 29–36 (39–49); length of premaxillary tooth band 22–30 (29–40); preoral length 8–14 (10–19); distance between tip and lateral angle of snout 10–15 (12– 20); snout width 17–24 (21–32); internasal width 13–20 (17–27); interorbital width 21–31 (28–41); occipital width 2–6 (3–8); body width over pectoral-fin bases 45– 77 (60–96); body depth at first dorsal-fin origin 70–127 (93–160); body depth at anal-fin origin 57–105 (75–132); prepelvic length 102–118 (129–154); preanus length 164–200 (209–252); preanal length 170–207 (216–262); isthmus–pelvic distance 44–57 (58–72); isthmus–anus distance 99–154 (131–194); isthmus–anal distance 103– 161 (135–202); pelvic–anal distance 61–106 (80–134); anus–anal distance 3–10 (4–13); pelvic-fin length 52–81 (68–109); pectoral-fin length 52–76 (69–102); predorsal length 114–136 (153–172); height of first dorsal fin 64–90 (81–118); length of first dorsal-fin base 27–37 (34–48); interdorsal length 37–88 (49–111); length of gill slit 15–20 (20–26); length of posterior nostril 3–7 (4–9); barbel length 13–20 (17–25); length of pyloric caecum 60 (78).

Size. Attains about 102 cm TL ( Mecklenburg et al. 2002).

Development. Larval morphology was briefly described by Merrett (2006) based on an illustration given by Fahay & Markle (1984: fig. 140d; as Coryphaenoides sp.).

Distribution. Known from the continental slope to hadal depths of the world’s oceans except the Arctic ( Iwamoto & Stein 1974; Wilson & Waples 1983; Iwamoto 1990; Endo & Okamura 1992; Mecklenburg et al. 2002; this study). In Japan, known only from off the Pacific coasts of Honshu, Hokkaido, and Shikoku at depths of 2698‾ 7433 m (Appendix 3-5F). Moderately common in its bathymetric range.

Remarks. Coryphaenoides armatus has been well described by previous authors; for a full description see Nybelin (1957; as Nematonurus armatus ), Iwamoto & Stein (1974), and Iwamoto & Sazonov (1988). This species has a cosmopolitan distribution, and was first recorded from Japan by Endo & Okamura (1992). Based on morphological and electrophoretic analyses, Wilson & Waples (1984) recognized two subspecies of C. armatus , namely, C. a. variabilis (G̹nther, 1878) confined to the North Pacific and C. a. armatus widely distributed in the other areas of the world’s oceans. According to their study, the North Pacific subspecies is characterized morphologically by having a narrower interorbital width (usually <24% HL in C. a. variabilis vs. usually Ż24% in C. a. armatus ), a shorter interdorsal length (usually ±60% HL vs. usually>60%), and higher counts of first dorsal- [II,9–10 vs. II,7–10 (usually II,8–9)] and pelvic-fin rays [20–23 total of both sides (mode 22) vs. 17–21 (20)]. The Japanese specimens examined agree well with C. a. variabilis in the meristic characters, with first dorsalfin rays modally II,9 (range II,9–10) and total pelvic-fin rays usually 22 (19–24). However, a great variation exists in both the interorbital and interdorsal spaces, and their values (relative to HL) become greater with growth ( Fig. 98 ).

Iwamoto & Sazonov (1998) found C. a. variabilis from northeastern Pacific to have much darker color than in C. a. armatus from the southeastern Pacific. They also noted the northeastern Pacific C. a. variabilis as having less-developed serrations along the first dorsal fin. The Japanese specimens examined are uniformly dark in color ( Fig. 97 ), and their dorsal-fin serrations are only weakly developed except in smaller specimens. These features are consistent with Iwamoto & Sazonov’s (1998) description of C. a. variabilis .

Many authors believed C. armatus to be a deep-slope/ upper-rise species, with its vertical distribution generally being restricted to about 2000–4300 m ( Iwamoto & Stein 1974; Wilson & Waples 1983, 1984; Endo & Okamura 1992; King & Priede 2008; Jamieson et al. 2012). However, the specimens examined here includes seven specimens collected from two hadal stations: NSMT-P 30199 (1 spec., 91.6 mm HL, 515+ mm TL) from the east of Tori-shima Island (30º10.12N, 146º49.14’E) by a fish trap deployed at a depth of 6273 m; and NSMT-P 97647– 97649, 97651, 97669 and 98008 (6 spec., 89.4–158 mm HL, 515–902+ mm TL) from the Japan Trench off Miyako (38.7983ºN, 144.1345ºE) at a depth of 7340–7433 m. These specimens confirm the occurrence of C. armatus in the hadal zone in the northwestern Pacific, representing the deepest record for the species. Coryphaenoides armatus was considered to be segregated bathymetrically from its sister species, C. yaquinae Iwamoto & Stein, 1974 (ca. 2000–4300 m in C. armatus vs. ca. 3400–6500 m in C. yaquinae ; Wilson & Waples 1983; Endo & Okamura 1992; Jamieson et al. 2012). However, the above finding suggests that C. armatus occurs, albeit rarely, in much deeper waters than previously thought and where C. yaquinae is predominantly distributed.

Relationships and comparisons. Coryphaenoides armatus belongs to the subgenus Nematonurus (sensu Iwamoto 1990) , and is most similar to C. yaquinae . The two species are readily distinguished by differences in dentition. In C. armatus , the mandibular teeth are arranged in one distinct row near the symphysis, whereas those of C. yaquinae are in two irregular series. It further differs from C. yaquinae in that inner premaxillary teeth, if present, are arranged in a single row (vs. 2–3 irregular rows or narrow band). Also, in large specimens of C. armatus , outer teeth are compressed distally, whereas those of C. yaquinae are conical with a slender tip ( Fig. 99A vs. B). In the northwestern Pacific off Japan, C. armatus is distinguished from C. yaquinae by the presence of scaly patches on the lower half of the suborbital area and the posterior portion of the mandibular rami. Spinulation of body scales is much coarser in C. armatus than in similar-sized specimens of C. yaquinae ( Fig. 100 A–B vs. C–D), although a considerable variation exists within each species.

Figures

FIGURE 97. Fresh specimens of Coryphaenoides armatus. (A) BSKU 96478, 37.1 mm HL, 202+ mm TL, off Kinkazan, Miyagi Pref., Pacific, 2698–2814 m depth; (B–C) BSKU 96459, 48.8 mm HL, 242+ mm TL, off Miyako, Iwate Pref., Pacific, 3150–3201 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. [Photos: H. Endo and N. Nakayama]

FIGURE 98. Scatter diagrams showing relationships of the (A) interorbital width and (B) interdorsal length (as % HL) to HL (mm) in Coryphaenoides armatus.

FIGURE 99. Dentition of two species of Coryphaenoides. (A) C. armatus, BSKU 37299, 107 mm HL; (B) C. yaquinae, BSKU 35737, 88.7 mm HL. Anterior views of the mouth. Preserved condition. [Photos: N. Nakayama]

FIGURE 100. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of two species of Coryphaenoides. (A–B) C. armatus, BSKU 37299, 107 mm HL; (C–D) C. yaquinae, BSKU 35734, 107 mm HL. (A, C) Views from above; (B, D) oblique views. [Photos: NSMT]