Coryphaenoides pectoralis ( Gilbert, 1891 )

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 196-200

Coryphaenoides pectoralis ( Gilbert, 1891)

[Japanese name: Mune-dara]

( Figs. 127–128 ; Appendix 3-7C)

Macrurus (Malacocephalus) pectoralis Gilbert, 1891:563 [original description; 2 syntypes: USNM 47235 and 47236, from off Washington, in 685–877 ftm (1253–1604 m)].

Macrurus (Nematonurus) magnus Gill & Townsend, 1897:234 (original description; holotype: USNM 48770 , from southwest of Pribilof Islands , Bering Sea).

Ateleobrachium pterotum Gilbert & Burke, 1912:94 , fig. 37 [original description; holotype: USNM 74398 , from off Avatcha Bay, east coast of Kamchatka, Albatross sta. 4798, 52º37.5ʹN, 158º50.0ʹE, in 300 ftm (549 m)].

Nematonurus pectoralis: Gilbert & Hubbs 1916:161 (new combination; first record from Japan; 3 spec. from Okhotsk Sea and south of Hokkaido; comparison with Alaskan population); Okada & Matsubara 1938:449 (in key; Japan; Japanese name: “Mune-dara”); Matsubara 1955:1308 (in key; Japan); Ueno 1965:19 (listed; Hokkaido); Matsubara 1965:504 (compiled; Japan); Maruyama 1971:33 (listed; Iwate Pref.); Hikita 1981:78, fig. 1 (spec. from Okhotsk Sea off Shiretoko Peninsula; erroneously noted Japanese name as “Himo-dara”; photo spec. represents C. pectoralis ).

Coryphaenoides pectoralis: Taranetz 1937:169 (new combination; listed; Soviet Far East); Lindberg 1959 (listed; southern Okhotsk Sea); Okamura 1970a:118, pl. XXV, text-fig. 49 (description; 14 spec. from southeast of Hokkaido, Pacific off Hachinohe, and Kominato); Ueno 1971:101 (listed; Hokkaido); Tominaga & Uyeno 1981:489 (listed; Japan); Shiogaki 1982:33 (listed; Aomori Pref.); Sawada 1983:109, 193, 251, 325, figs. 60, 140 [brief description; 7 spec. from Pacific off Tohoku and Okhotsk Sea; photos based on HUMZ 78178 and HUMZ 78604 (not 78064)]; Amaoka & Nakaya 1983:44, fig. 60 (compiled; northern Japan); Okamura 1984b:95, pl. 82, fig. A (compiled); Okamura 1988:95, pl. 82, fig. A (compiled); Maeda & Maruyama 1991:366 (listed; Hokkaido); Nakabo 1993:362 (in key; Japan); Hori 1996:28 (listed; Ibaraki Pref.); Okamura 1997:125, fig. 4 (compiled); Funabashi 1998:85 (listed; Ibaraki Pref.); Nakabo 2000:426 (in key; Japan); Zama 2001:39 (listed; Miyagi Pref.); Nakabo 2002:426 (in key; Japan); Shiogaki et al. 2004:55 (listed; Pacific off Aomori Pref.); Senou et al. 2006:420 (listed; Sagami Sea); Kitagawa et al. 2008:40, unnumbered fig. (brief description; spec. from Pacific off Tohoku); Balanov et al. 2009:672 (14 spec. listed from Pacific off Tohoku; midwater captures); Shinohara et al. 2009:708 (4 spec. listed from Pacific off Tohoku); Endo et al. 2010:273, figs. 2–5 (larval description; 1 spec. from northwestern Pacific off Hokkaido); Amaoka et al. 2011:128, fig. 160 (compiled; Hokkaido); Nakabo & Kai 2013:502 (in key; Japan); Amaoka et al. 2020:160, fig. 214 (listed; Hokkaido); Motomura 2020:39 (listed; Japan).

Coryphaenoides (Nematonurus) pectoralis: Okamura 1970b : table 1 (listed; Japan).

Ateleobranchium [sic] pterotum: Ueno 1971:101 (listed; northern Kurile Islands; new Japanese name: “Nodoguro-hige”).

Albatrossia pectoralis: Iwamoto 1990:110 , fig. 236 (synopsis); Endo et al. 1993:219, fig. 2 (larval description; 4 spec. from North Pacific); Amaoka et al. 1995:101, fig. 149 (compiled; northern Japan); Shinohara et al. 1996:168 (2 spec. listed from Pacific off Tohoku); Maeda & Tsutsui 2003:488 (listed; Hokkaido); Motomura 2020:39 (listed; Japan).

Diagnosis. Pelvic-fin rays usually 7 (rarely 5–6 or 8). Snout conical, moderately protruding beyond upper jaw. Tip and lateral angles of snout lacking prominent tubercles; scales along head ridges not coarsely modified. Mouth large, posterior margin of upper jaw extending to vertical through hind rim or orbit or beyond; upper-jaw length 40–44% HL; lateral corner of mouth not restricted by skin folds. Outermost gill slit moderately wide, length 16–22% HL. Barbel short, slender, length 5–8% HL. Teeth prominent, conical, slender, in 2 irregular series in premaxillary, 1 distinct row in dentary. Body scales covered with short, reclined, needle-like spinules in widely divergent rows; 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 9.5–12.5. Top of snout fully scaled; ventral surfaces of head almost completely scaled except for underside of snout. Interdorsal space less than first dorsal-fin base length. First dorsal fin small, low, its height 43–50% HL; second spinous ray weakly serrated along its leading edge; first dorsal-fin rays II,8–10. Pelvic fin small, not reaching anal-fin origin when depressed. Body pale to dark brown.

Material examined. 18 specimens. Japan : BSKU 85148 (1, 83.1 mm HL, 490+ mm TL) , BSKU 85149 (1, 79.5 mm HL, 469+ mm TL) , BSKU 85150 (1, 71.0 mm HL, 375+ mm TL), Pacific off Tohoku, 700 m, T/ V Tanshumaru, sta. D-700, beam trawl, coll. H. Endo, 18 Apr. 1998 ; BSKU 19016 (1, 108 mm HL, 617+ mm TL), southeast of Oshima Island , Shichito-Iojima Ridge, 34.5750ºN, 139.6583ºE, 1560–1570 m, FRV Soyo-maru, sta. 51, beam trawl, 10 Nov. 1958 ; BSKU 97798 (1, 87.1 mm HL, 472+ mm TL), off Iwaki , 36.9398ºN, 141.7007ºE, 967–1219 m, FRV Wakataka-maru, sta. 51, otter trawl, 5 Nov. 1995 ; BSKU 96460 (1, 34.6 mm HL, 192+ 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 97808 (1, 214 mm HL, 1010+ mm TL) , BSKU 97809 (1, 135 mm HL, 797+ mm TL) , BSKU 97810 (1, 125 mm HL, 719+ mm TL) , BSKU 97811 (1, 151 mm HL, 828+ mm TL), off Kuji , 40.0613ºN, 142.6825ºE, 1005–1016 m, R/ V Tanseimaru, cr. KT-93-15, sta. M3, 3-m ORE beam trawl, coll. Y. Machida, 18 Nov. 1993 ; BSKU 97799 (1, 104 mm HL, 617+ mm TL) , BSKU 97800 (1, 65.8 mm HL, 440+ mm TL), off Kitakami River , 38.5318ºN, 142.3370ºE, 772– 783 m, FRV Wakataka-maru, sta. 32, otter trawl, 28 Oct. 1995 ; BSKU 97806 (1, 92.8 mm HL, 603 mm TL), southsoutheast of Akkeshi , 42.6052ºN, 144.9938ºE, 1113–1161 m, R/ V Tansei-maru, cr. KT-93-15, sta. T8, 3-m ORE beam trawl, coll. Y. Machida, 16 Nov. 1993 ; * BSKU 114809 (1, 50.6 mm HL, 280+ 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 114822 (1, 105 mm HL, 610+ mm TL), southeast of Tokachi , 42.3317ºN, 143.9585ºE, 719 m, FRV Wakataka-maru, sta. F-700, otter trawl, coll. R. Misawa, 10 Jun. 2014 ; * BSKU 114903 (1, 226 mm HL, 1100+ mm TL) , * BSKU 114905 (1, 161 mm HL, 859+ mm TL), east-southeast of Cape Erimomisaki , 42.2820ºN, 143.8012ºE, 572 m, FRV Wakataka-maru, sta. G-550, otter trawl, coll. R. Misawa, 9 Jun. 2014 . Bering Sea : BSKU 35224 (1, 147 mm HL, 821+ mm TL), 58.6633ºN, 177.9167ºE, 735–800 m, 26 Jun. 1979 .

Counts and measurements. Based on 14 specimens (34.6–214 mm HL, 192+–1010+ mm TL). Counts: first dorsal-fin rays II,8–10; pectoral-fin rays i14–i19; pelvicfin rays 5–8; gill rakers on first arch (outer/inner) 5–8/11– 16, on second arch 11–13/10–13; transverse scale rows below first dorsal-fin origin 11.5–15, below first dorsalfin midbase 9.5–12.5, below second dorsal-fin origin 7.5– 12, above anal-fin origin 29–43.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 26–27 (32–36); orbit diameter 19–30 (26–38); postorbital length 49–57 (62–75); postrostral length 74–79; orbit–preopercle distance 40–46 (51–60); suborbital width 8–12 (11–16); upper-jaw length 40–44 (52–56); length of rictus 34–38 (44–50); length of premaxillary tooth band 29–33 (38– 43); preoral length 9–12 (11–16); distance between tip and lateral angle of snout 10–12 (13–16); snout width 16– 20 (20–26); internasal width 15–18 (20–25); interorbital width 23–27 (30–35); occipital width 10–14 (13–18); body width over pectoral-fin bases 34–72 (46–94); body depth at first dorsal-fin origin 55–82 (74–105); body depth at anal-fin origin 41–75 (54–99); prepelvic length 96–105 (124–138); preanus length 142–164 (189–217); preanal length 146–177 (195–226); isthmus–pelvic distance 36– 44 (47–58); isthmus–anus distance 83–109 (111–139); isthmus–anal distance 88–115 (118–147); pelvic–anal distance 51–79 (68–101); anus–anal distance 3–7 (5–10); pelvic-fin length 40–53 (52–68); pectoral-fin length 51– 66 (66–84); predorsal length 99–113 (132–148); height of first dorsal fin 43–50 (55–66); length of first dorsal-fin base 21–30 (28–40); interdorsal length 11–20 (14–27); length of gill slit 16–22 (22–29); length of posterior nostril 5–8 (7–10); barbel length 5–8 (6–11).

Size. Coryphaenoides pectoralis is by far the largest species of grenadiers.According to biological information summarized by Orlov & Tokranov (2008), it attains about 220 cm TL ( Toponogov & Kurennoi 1986). The largest specimen examined is HUMZ 69383 collected from the Pacific off Hokkaido, measuring 158 cm TL.

Variation. In the smaller specimens examined, the body scales are covered with short, reclined, needlelike spinules giving a more or less spiny appearance to body surfaces ( Fig. 128 A–B). The spinules become weaker with increasing body size, and those of the larger specimens examined were always difficult to distinguish ( Fig. 128 C–D).

Sexual dimorphism. Orlov & Tokranov (2008) reported that C. pectoralis collected from the northwestern Pacific off the northern Kuril Islands exhibits sexually dimorphic differences in body size: females attain a larger size than males (135 cm maximum TL vs. 97 cm) with the body weight reaching up to 11.8 kg (vs. 3.6 kg).

Development. Larval morphology was described by Endo et al. (1993, 2010), and Endo (1996, 2014) [see also Ambrose (1996)]. Based on a pelagic larva with a nearly complete tail, Endo et al. (2010) reported the reliable numbers of second dorsal- and anal-fin rays, and total vertebrae of this species as 156, 137, and 14 + 117 = 131 respectively.

Distribution. Widely distributed in the North Pacific from Japan to the United States, including the Okhotsk and Bering Seas as well as the Emperor Seamounts ( Iwamoto & Stein 1974; Borets 1986; Iwamoto 1990; Mecklenburg et al. 2002; this study). Depth range varied from 140 to 3201 m, but usually shallower than 1500 m ( Orlov & Tokranov 2008; this study). Arkhipkin et al. (2010) recently reported an 815 mm TL specimen from off the Falkland Islands in the southwestern Atlantic (as Albatrossia pectoralis ), suggesting its antipodal migration through the Drake Passage [this specimen was previously reported as Albatrossia cf. pectoralis by Brickle & Laptikhovsky (2002)]. In Japan, known from off the Pacific coasts southward to the Izu Peninsula (138.96ºE) and the southern Okhotsk Sea (Appendix 3-7C). Depth range off Japan 152–3201 m. Common, especially in the north of Choshi (35.74ºN; Chiba Pref.).

Remarks. Coryphaenoides pectoralis has been well described by previous authors, and thus there is no need for repetition here. For a full description see Okamura (1970a) and Iwamoto & Stein (1974). This species is among one of the most abundant continental slope fishes found in the North Pacific ( Orlov & Tokranov 2008). The biology of this species off the Kuril and Kamchatka Islands was well investigated by Orlov & Tokranov (2008).

Relationships. There has been no general consensus about the generic affiliation of this common grenadier. Gilbert (1891) originally described the species under the name Macrurus (Malacocephalus) pectoralis . Subsequently, it was transferred to Nematonurus G̹nther, 1887 (originally described as a subgenus of Macrourus Bloch, 1786 ) by Goode & Bean (1896), whereas Jordan & Gilbert (in Jordan & Evermann 1898) established its own genus Albatrossia . As far as I know, Fowler (1936) was the first who synonymized Albatrossia with Coryphaenoides , and Taranetz (1937) subsequently listed this species as a species of Coryphaenoides . Okamura (1970a) provided the species’ description under Coryphaenoides , although Nematonurus retained subgeneric status; he regarded Albatrossia as a junior synonym of Coryphaenoides . Iwamoto & Stein (1974) followed Okamura’s (1970a) conclusion, but Iwamoto & Sazonov (1988) latter resurrected Albatrossia as a separate genus distinct from Coryphaenoides . During the past three decades, some authors considered the species to be the only representative of Albatrossia (e.g., Iwamoto 1990; Endo et al. 1993; Shinohara et al. 1996; Mecklenburg et al. 2002), while others regarded the species as a member of Coryphaenoides (e.g., Okamura 1984b, 1988; Sawada 1983; Nakabo 1993, 2000, 2002; Senou et al. 2006; Endo et al. 2010; Nakabo & Kai 2013). The difference of opinion is largely due to unique morphological features of this species. Despite their close similarity in general appearance, it readily differs from all other species of Coryphaenoides in having several autapomorphic features including: a horizontally elongate otolith with a comb-like ventral margin; 2 rete-gas gland complexes in a reduced swim bladder; teeth in 2 irregular series in the premaxillary, and a distinct 1 row in the dentary.

Recent molecular analyses, by contrast, showed that the species is deeply nested within a clade of Coryphaenoides , suggesting Albatrossia to be a junior synonym of that taxon ( Wilson et al. 1991; Wilson 1994; Morita 1999; Wilson & Attia 2003; Roa-Varón & Ortí 2009). However, their results also imply that Albatrossia might be recognized as a subgenus of Coryphaenoides . According to the most comprehensive tree based on the RAG1 and mitochondrial ribosomal genes ( Roa-Varón & Ortí 2009: fig. 3), the subgenus Coryphaenoides (sensu Iwamoto 1990) is divided into two clades, with “ pectoralis ” belonging to one that excludes C. rupestris Gunnerus, 1765 (type species of Coryphaenoides ). Their tree also shows that “ pectoralis ” forms a small clade with C. acrolepis ( Bean, 1884) and C. cinereus ( Gilbert, 1896) , although their close relationship does not seem to be supported by morphological characters. It is obvious that further investigations are necessary to determine whether Albatrossia deserves subgeneric status within Coryphaenoides . If so, there is an additional question around how many species are included in this group. In the present study, Albatrossia is tentatively regarded as a subgenus of Coryphaenoides , and C. pectoralis is considered to be its only representative.

Comparisons. Coryphaenoides pectoralis is highly distinctive among the genus in its unique dentition: the premaxillary teeth are arranged in two irregular series, whereas those in the dentary are in one distinct row. The small swim bladder of C. pectoralis , with two rete-gas gland complexes, also distinguishes the species from the other members of Coryphaenoides [vs. swim bladder well developed with 4–7 rete-gas gland complex (fide Iwamoto & Sazonov 1988:38)]. It further differs from all other congeners in having a horizontally elongate otolith with a comb-like ventral margin (vs. otolith moderately high, not comb-like ventrally). For more comparisons with Japanese congeners, see the key to species provided in this study.

Figures

FIGURE 127. Fresh specimens of Coryphaenoides pectoralis. (A) BSKU 96460, 34.6 mm HL, 192+ mm TL, off Miyako, Iwate Pref., Pacific, 3150–3201 m depth; (B) BSKU 114809, 50.6 mm HL, 280+ mm TL, south of Kushiro, Hokkaido, Pacific; (C) BSKU 114822, 105 mm HL, 601+ mm TL, southeast of Tokachi, Hokkaido, Pacific, 719 m depth; (D) BSKU 114905, 161 mm HL, 859+ mm TL, east-southeast of Cape Erimomisaki, Hokkaido, Pacific, 572 m depth; (E–G) BSKU 114903, 226 mm HL, 1100+ mm TL, collected with BSKU 114905 (E, reversed). (A–E) Lateral views; (F) dorsal and (G) ventral views of the head and trunk. [Photos: (A) H. Endo and N. Nakayama; (B–G) N. Nakayama]

FIGURE128. Scanning electronmicrographsshowingbodyscales (fromthe dorsumbelowthe interdorsal space) ofCoryphaenoides pectoralis. (A–B) BSKU 85150, 71.0 mm HL; (C–D) BSKU 97811, 151 mm HL. (A, C) Views from above; (B, D) oblique views. [Photos: NSMT]