Coelorinchus hige Matsubara, 1943

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 65-72

Coelorinchus hige Matsubara, 1943

[Japanese name: Kata-hige]

( Figs. 21B , 43–45 ; Table 2 ; Appendix 3-2E)

Coelorhynchus hige Matsubara, 1943:144 , fig. 6 (original description; holotype: SKFC 6, from Suruga Bay off Heta; new Japanese name: “Kata-hige”); Kuroda 1951:391 (listed; Suruga Bay); Matsubara 1955:1313 (in key; Japan); Okamura 1970a:193 [description after Matsubara (1943)]; Tominaga & Uyeno 1981:488 (listed; Japan); Ozawa 1983:13 (listed; off Makurazaki, Kagoshima Pref., East China Sea).

Coelorhynchus asteroides Okamura, 1963a:21 , fig. 1 [original description; holotype: FAKU 23801, from off Owase (misspelled as Owashi); 7 paratypes from Heta, Owase and Mimase; new Japanese name: “Hoshihige”]; Kamohara 1964:95 (listed; Kochi Pref.); Okamura 1970a:189, pl. XLI, text-figs. 81–82 [description; 8 spec. from Suruga Bay, Owase (misspelled as Owashi), and Mimase]; Kuroda 1971:56 [listed from Suruga Bay after Okamura (1970a)]; Tominaga & Uyeno 1981:488 (listed; Japan).

Coelorhynchus (Oxymacrurus) asteroides: Okamura 1970b : table 1 (listed; Japan).

Coelorhynchus (Oxymacrurus) hige: Okamura 1970b : table 1 (listed; Japan).

Coelorinchus asteroides: Yatou 1984:235 , 369, fig. 167 (brief description; 10 spec. from Okinawa Trough; photo based on BSKU 29833); Okamura 1984b:97, pl. 83, fig. F (compiled); Okamura 1988:97, pl. 83, fig. F (compiled); Okamura 1997:127, fig. 13 (compiled); Shao et al. 2008b: table 2 (3 spec. listed from northeastern and southwestern Taiwan); Nakabo & Kai 2013:511 (in key; Japan); Iwamoto et al. 2015:50 (brief description; 8 spec. from northeastern and southwestern Taiwan, and Philippines); Motomura 2020:38 (listed; Japan).

Caelorinchus asteroides : Nakabo 1993:370 (in key; Japan); Shinohara & Matsuura 1997:290 (listed; Suruga Bay); Nakabo 2000:434 (in key; Japan); Shinohara et al. 2001:304 (listed; Tosa Bay); Nakabo 2002:434 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Chiou et al. 2004a:43, fig. 9 (brief description; 2 spec. from Da-xi and Dong-gang; first record from Taiwan); Shinohara et al. 2005:416 (listed; Ryukyu Islands); Furuhashi et al. 2010: table 2 (39 spec. listed from northern Okinawa Trough).

Caelorinchus (Oxymacrurus) asteroides : Chiou et al. 2004a: table 1 (listed; Taiwan).

Diagnosis. Light organ externally represented by short, narrow, naked streak immediately anterior to anus, its anterior margin falling far short of line connecting inner pelvic-fin bases. Underside of head almost completely naked; dorsal surface of snout fully scaled, except narrow naked clefts along each side of median rostral ridge. Nasal fossa usually naked. Snout long, sharply pointed, length 57–83% PRL, becoming proportionally shorter with growth; dorsal profile of snout almost straight in lateral view. Terminal snout scute short, broad, arrowheadshaped, dorsoventrally flattened, length 11–18% PRL. Scales on median rostral ridge covered with radiating rows of spinules. Lateral nasal ridge completely supported by nasal bone, not strongly convex when viewed dorsally. Anus slightly separated from anal-fin origin. Premaxillary teeth small, conical, arranged in short, uniformly wide band, none especially enlarged; posterior margin of tooth band falling far short of lateral corner of mouth. Body scales covered with short, reclined, keel-like spinules in narrowly divergent, saw-toothed ridges; every spinule row complete, extending to posterior scale margin; spinules in each row greatly overlapping, closely adjoined to one another, but generally free at tips; buttresses scarcely developed. Occipital scales covered with short, erect, recurved, needle-like spinules in widely divergent comblike rows. Height of first dorsal fin 71–106% PRL; interdorsal length 51–70% PRL; pyloric caeca 47–49. Body darker dorsally, paler ventrally; no obvious body markings in adults, but juveniles with small dark spots on posterior part of tail; underside of head dusky; lips white; oral cavity blackish; gular and branchiostegal membranes pale; pelvic fins dusky.

Material examined. 30 specimens. Holotype of Coelorhynchus asteroides: FAKU 23801 (85.5 mm HL, 376+ mm TL), Owase fish market, Mie Pref., Kumanonada, Japan, bottom trawl, 24 Oct. 1954. Paratypes of C. asteroides: FAKU 29115 (1, 76.2 mm HL, 266+ mm TL), Mimase fish market, bottom trawl, date unknown; FAKU 21513 (1, 60.2 mm HL, 269+ mm TL) , FAKU 24909 (1, 67.5 mm HL), Owase fish market, Kumano-nada , bottom trawl, date unknown. Non-types: Japan : BSKU 106771 (1, 66.1 mm HL, 268 mm TL) , BSKU 106822 (1, 61.2 mm HL, 255+ 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 50881 (1, 30.0 mm HL, 108+ mm TL), off Nomaike, Kagoshima, East China Sea , F/ V Maruko-maru, bottom trawl, coll. M. Yamashita and Y. Ohashi, 10 Sept. 2010 ; BSKU 109039 (1, 84.2 mm HL, 351+ mm TL) , BSKU 109040 (1, 88.2 mm HL, 401+ 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 ; SNFR 14555 (1, 110 mm HL, 461+ mm TL), East China Sea , 31.4372ºN, 128.3418ºE, 233–303 m, F/ V Choun-maru, No. 6, sta. C6-j, tr. 119, bottom trawl, coll. T. Jintoku, 29 Sept. 2009 ; BSKU 29833 (1, 74.0 mm HL, 299+ mm TL) , BSKU 33819 (1, 76.1 mm HL, 330 mm TL) , BSKU 33820 (1, 70.7 mm HL, 297 mm TL) , BSKU 33821 (1, 72.4 mm HL, 300+ mm TL), northwest of Amami-oshima Island, Okinawa Trough , 30.4815ºN, 127.8432ºE, 320– 360 m, F/ V Yuryo-maru, No. 8, sta. 3-T8, bottom trawl, coll. H. Maeda, 28 Oct. 1979 ; BSKU 28286 (1, 75.5 mm HL, 289+ mm TL), northwest of Amami-oshima Island, Okinawa Trough , 29.7500ºN, 127.5000ºE, 325–360 m, F/ V Ryoan-maru, No. 28, tr. 70, bottom trawl, coll. Y. Kinoshita and S. Hagino, 19 Mar. 1978 ; * BSKU 27032 (1, 70.2 mm HL, 223+ mm TL), northwest of Amamioshima Island, Okinawa Trough , 29.9267ºN, 127.7483ºE, 360 m, F/ V Yuryo-maru, No. 8, tr. 20, bottom trawl, coll. Y. Kinoshita and S. Hagino, 4 Feb. 1978 ; BSKU 29773 (1, 69.7 mm HL, 297+ mm TL), northwest of Okinawajima Island, Okinawa Trough , 28.7000ºN, 125.9333ºE, 320 m, F/ V Yuryo-maru, No. 8, sta. 2-T7, bottom trawl, coll. M. Hirose and T. Kume, 12 Oct. 1979 ; BSKU 29032 (1, 71.2 mm HL, 222+ mm TL), Mimase fish market, 4 Nov. 1978 ; BSKU 879 (1, 47.1 mm HL, 198+ mm TL), Mimase fish market, bottom trawl, coll. T. Kamohara, 16 Jan. 1951 ; BSKU 9684 (1, 67.7 mm HL, 297 mm TL) , BSKU 9685 (1, 67.1 mm HL, 274+ mm TL), Mimase fish market, bottom trawl, coll. T. Kamohara, 17 Mar. 1949 ; BSKU 275 (1, 63.1 mm HL, 264 mm TL) , BSKU 276 (1, 58.1 mm HL, 256 mm TL) , BSKU 277 (1, 64.4 mm HL, 263+ mm TL) , BSKU 278 (1, 65.4 mm HL, 291 mm TL) , BSKU 279 (1, 58.2 mm HL, 254+ mm TL) , BSKU 280 (1, 57.2 mm HL, 241+ mm TL), Mimase fish market, bottom trawl, coll. T. Kamohara, 20 Feb. 1950 ; BSKU 9683 (1, 63.4 mm HL, 276+ mm TL), Mimase fish market, bottom trawl, coll. T. Kamohara, 30 Jan. 1951 ; BSKU 112434 (1, 83.6 mm HL, 336+ mm TL) , BSKU 112451 (1, 72.0 mm HL, 310+ mm TL), off Susaki, Tosa Bay , 320–380 m, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama et al., 9 Mar. 2014 .

Redescription based on Japanese specimens. General features are shown in Figs. 21B , 43–44 . Counts and measurements are given in Table 2 . Body deepest at first dorsal-fin origin, progressively tapering to long, laterally compressed tail. Trunk short, moderately compressed, width over pectoral-fin bases 1.1–1.3 in depth below first dorsal-fin origin. Head large, HL about 3.6–4.5 in TL. Snout long, protruding greatly beyond upper jaw, length 1.3–1.7 times as long as orbit diameter; dorsal contour of snout almost straight in lateral view; lateral nasal ridge completely supported by nasal bone; anterolateral margins of snout moderately convex when viewed dorsally. Orbit large, its greatest diameter 0.9–1.3 in postorbital length. Interorbital space flat, width 1.1– 1.5 in orbit diameter. Mouth moderate in size, inferior, protrusible, upper-jaw length 1.0– 1.3 in orbit diameter; posterior margin of maxilla extending to below midorbit or beyond, but not reaching hind margin of orbit; lateral corner of mouth moderately restricted by skin folds; lips thin, slightly papillose near tooth bands. Suborbital region divided by longitudinal bony ridge passing from tip of snout to posteroventral angle of opercle; its upper half almost vertical, lower half sharply inclined mesially. Preopercle large, posterior margin inclined, forming moderately angular lobe at posteroventral corner. Subopercle prolonged ventrally as slender flap; posterior margin deeply concave. Gill membranes broadly connected across, and attached mesially to isthmus, with slight posterior free fold. Outer gill slit moderately restricted by skin folds, length 2.0– 3.4 in orbit diameter (1.8 in largest specimen; SNFR 14555, 101 mm HL). Gill rakers small, low, tubercular, armed with short, fine spines; no rakers on outer side of first arch (rudimentary raker occasionally found in larger specimens) and inner side of fourth arch; gill filaments moderately long. Chin barbel slender, tapering into fine tip; length 2.1–4.7 in orbit diameter.

Anus slightly separated from anal-fin origin by 1–2 scale rows. Light organ externally represented by short, narrow, naked streak, extending from anus forward to about midway between anus and outer pelvic-fin bases, its anterior margin falling far short of line connecting inner pelvic-fin bases. Pyloric caeca 47–47 (based on 3 paratypes of C. asteroides and BSKU 106771 ), rete-gas gland complexes 2 (based on BSKU 106771 ).

Teeth small, sharp, conical, gently incurved, in narrow bands in both jaws. Premaxillary teeth in short, uniformly wide band, with about 6 tooth rows near symphysis; posterior margin of tooth band falling far short of lateral corner of mouth; teeth becoming progressively smaller inwardly. Mandibular teeth uniformly small, in broad tapered band, with about 5–6 tooth rows across widest point near symphysis; band abruptly narrowing posteriorly, its posterior margin extending beyond lateral corner of mouth. All teeth deeply embedded in thick layer of gum papillae.

Scales on body large, thin, not deciduous, covered with short, reclined, keel-like spinules in narrowly divergent rows ( Fig. 45 A–D); in 88.2 mm HL specimen (BSKU 109040), those on dorsum below interdorsal space with 8–9 rows of spinules; middle row longest with about 8–9 spinules, but not especially high or enlarged compared with adjacent rows; every spinule row complete throughout; spinules forming angle of about 40º to scale surface; spinules greatly overlapping, closely adjoined to one another, but their distal tips usually free, forming sawtoothed ridges; spinules increasing in height posteriorly, but last spinule in each row barely extending beyond posterior scale margin; buttresses of spinules scarcely developed; no reticulate structures on unexposed potion. Body fully scaled except for fins and light organ.

Scales on head ridges stout, thickened; those on median rostral ridge covered with radiating rows of spinules. Terminal snout scute short, broad, arrowheadshaped, dorsoventrally flattened, its length 2.8–4.4 in orbit diameter. Supraoccipital scute stout, enlarged, armed with single row of spinules; posttemporal scutes similar to that on supraoccipital, but spinules arranged in multiple rows. Occipital scales covered with short, erect, needle-like spinules in widely divergent rows ( Fig. 45 E–F); spinules recurved posteriorly, but scarcely imbricated, independent from one another, forming comb-like ridges that increase in height posteriorly; scales on dorsal surfaces of snout posterior to leading edges armed with cluster of short, erect, needle-like spinules. Other scales on head variable in size, generally similar to those on body, but spinules more erect and spinule rows more divergent; those on opercle, preopercle, and postorbital and supratemporal canals largest. Nasal fossa usually naked (a few tiny scales occasionally present anteroventrally). Dorsal surfaces of snout almost completely scaled; pair of small naked areas posterior to lateral nasal ridges and along each side of median rostral ridge. Underside of head almost completely naked; a few small scales often present on lower portion of preopercle and above posterior margins of lower jaws.

No open pores along cephalic sensory canals. Free neuromasts on ventral surface of head poorly marked, not discernible. Anterior nostril small and oval; posterior elongated slit. Grooved lateral line complete throughout.

Origins of first dorsal and pelvic fins on about same vertical; pectoral-fin base slightly anterior to this level. First dorsal fin moderately high, its height 2.0–3.6 times as long as its base length; second spinous ray not elongated, smooth along its leading edge (1–2 rudimentary denticles rarely present distally); its tip usually extending to second dorsal-fin origin or beyond when laid back. Interdorsal space 1.4–2.4 (usually Ż1.7) times as long as first dorsalfin base length. Second dorsal fin originating posterior to vertical through anal-fin origin (above base of 5th–10th anal-fin rays). Outer pelvic-fin ray slightly prolonged, with filamentous tip.

Color when fresh ( Fig. 43 ). Head and body purplish gray dorsally, whitish ventrally; silvery reflection slightly developed over lateral surface of body; abdomen pale in lateral and ventral views; opercle and dorsum body iridescent soon after capture; first dorsal fin darker distally, but paler basally; pectoral fin dark dusky; pelvic fin dusky; distal margin of anal fin narrowly black posteriorly.

Color in alcohol ( Figs. 21B , 44 ). Head and body generally light brown dorsally, paler ventrally; no obvious body markings in adults, but juveniles with small dark spots on posterior part of tail ( Fig. 21B ); underside of head dusky; abdomen dark violet in ventral view, but chest paler; lips white; oral and gill cavities blackish; gill rakers and filaments pale, arches dusky; gular and branchiostegal membranes pale; first dorsal fin uniformly dark, but second spinous ray blackish; second dorsal fin immaculate; anal fin paler anteriorly, but prominently darker posteriorly; pectoral and pelvic fins generally dusky; outer pelvic-fin rays paler distally.

Size. To about 46 cm TL ( SNFR 14555 , 416 + mm TL, Okinawa Trough , Japan).

Distribution. Restricted to Japan and Taiwan (Appendix 3-2E). Known from off the Pacific coasts of southern Japan northward to the Izu Peninsula (138.96ºE), Okinawa Trough, and northern South China Sea, at depths of 233– 420 m. Common in the East China Sea, but seemingly rare in the Pacific off southern Japan.

Comments on holotype. Coelorinchus hige was described from a single specimen collected from Suruga Bay off Heta, Shizuoka Pref., Japan. It is one of the six species of grenadiers described by Matsubara (1943), whose holotypes were originally registered in the Sigenkagaku Fish Collection of the Research Institute for Natural Resources, Tokyo. These species are: C. kamoharai (holotype SKFC 4; ex. Matsubara’s personal number 2498); C. hige (SKFC 6); C. longissimus (SKFC 5; ex. 1592); C. vermicularis (SKFC 3; ex. 2495) (a junior synonym of C. multispinulosus Katayama, 1942 ); Lionurus abei (SKFC 7; ex. 4909) [a junior synonym of Nezumia proxima (Smith & Radcliffe in Radcliffe, 1912)]; and L. japonicus (SKFC 8; ex. 1951) (= Kumba japonica ). Unfortunately, the building of the institute was destroyed by a bombing raid in 1945, and these holotypes are now believed to be lost ( Eschmeyer 1998, Fricke et al. 2020). These types, if still extant, are most likely to be present in the ichthyological collection of the Maizuru Fisheries Research Station, Kyoto University, Maizuru, where Matsubara worked after the war. However, none were found in the FAKU collection, despite thorough surveys by the present author in 2009–2010 and 2016–2018.

In the original description of C. hige, Matsubara (1943) provided an excellent description of the holotype, with an illustration of a body scale taken from the dorsum below the interdorsal space (Matsubara 1943: fig. 6). Although the holotype is apparently lost, its diagnostic features were adequately detailed in Matsubara’s description, viz., snout length 39% HL; orbit diameter 28% HL; interorbital width 38% HL; postorbital length 33% HL; pelvic–anus distance 33% HL; interdorsal length 38% HL; barbel length 11% HL; teeth in bands in both jaws, none especially enlarged; premaxillary tooth band moderately broad throughout its length; short light organ immediately anterior to anus, its length as long as pupil diameter; body scales covered with 7–9 divergent rows of spinules; nasal fossa lacking scales; underside of snout almost completely naked; second dorsal-fin origin far posterior to vertical through anal-fin origin and above base of eighth anal-fin ray. Subsequently, Matsubara (1955:1313), in his key to species of Japanese grenadiers, noted that C. hige has five scales below the midbase of the first dorsal fin.

Nomenclatural discussion. Although the name C. hige is available under the ICZN (1999), many recent authors did not mention the presence of this species (e.g., Okamura 1984b; Nakabo 2002; Nakabo & Kai 2013). Iwamoto (1990) is one of the few authors who referred to C. hige , implying its close similarity with C. asteroides Okamura, 1963 . In his key to species of Coelorinchus , C. hige keys out together with C. asteroides at 27a, but no further couplet is provided to distinguish the two species ( Iwamoto 1990:130).

Coelorinchus asteroides was described by Okamura (1963a) based on eight specimens collected from off the Pacific coasts of southern Japan, and all subsequent authors have considered the species valid (e.g., Okamura 1970a, 1984b; Yatou 1984; Iwamoto 1990; Nakabo 1993, 2000, 2002; Nakabo & Kai 2013; Iwamoto et al. 2015). The holotype ( Fig. 44 ) and two of the paratypes (FAKU 21513 and 29115) were examined in the course of this study. Unfortunately, five paratypes (FAKU 7057, 24909, 25194, 33910, and 33981) were not found in the FAKU collection during the author’s visit in 2009. Subsequently, a specimen labeled as a paratype of C. asteroides was rediscovered during the 2010 visit.Although it neither bore a catalog number nor had locality data, it is characterized by having the following counts and measurements: first dorsal-fin rays II,8; pectoral-fin rays i17; pelvic-fin rays 7; inner gill rakers on first arch 6; HL 67.5 mm; snout length 26.0 mm (39% HL); orbit diameter 20.0 mm (30%); postorbital length 22.5 mm (33%); suborbital width 9.3 mm (14%); upper-jaw length 16.1 mm (24%); interorbital width 16.2 mm (24%); interdorsal length 28.2 mm (42%). These data completely match with those given by Okamura (1963a: table 1) for FAKU 24909, a paratype of C. asteroides collected from Owase; thus, the specimen is considered here to bear the catalog number of this specimen.

According to Okamura (1963a:25), C. asteroides is similar in general appearance to C. hige , but differs in having 3.5 scales below the midbase of the first dorsal fin (vs. 5 in C. hige ), the postorbital length less than the pelvic–anus distance (vs. almost equal), and the scales on the median rostral ridge covered with radiating rows of spinules (vs. “… without divergent carinae of spinules”). Subsequently, Okamura (1970a:154) further distinguished C. asteroides from C. hige by the absence of scales on the underside of the head (vs. “underside of head with a triangular scaly area at the distal part”). However, these proposed differences appear to be too subtle or obscure to reflect their specific separation.

An examination of the available types and additional specimens of C. asteroides , along with the original description of C. hige , revealed that the two species are not separable morphologically. In the beginning of this study, the additional specimens were treated as C. asteroides for convenience of comparison, because some were already reported under this name by previous authors ( Okamura 1984b, 1988, 1997; Yatou 1984). All counts and measurements of the holotype of C. hige (based on Matsubara 1943, 1955) fall within the range of variation of the C. asteroides specimens examined, including the numbers of scale rows and the pelvic–anus distance ( Table 2 ). Unfortunately, it is unknown how the spinules on the midrostral scales were arranged in the holotype of C. hige , because Matsubara (1943:145) described only the holotype as having the scales “without carinae diverging outward and backward from front of the scales” [sic, probably meaning the spinules are not arranged in distinct rows]. In C. asteroides , the midrostral scales are generally covered with radiating rows of spinules that originate slightly anterior to the center of the scale. However, the rows are often irregular in small specimens, and the condition agrees well with Matsubara’s (1943) description. Furthermore, the holotype of C. hige was somewhat small, measuring 256 mm TL (fide Matsubara 1943:144). Matsubara (1943) described C. hige as having “the underside of the head naked except the small triangular area at the distal part where the several small spinous scales are crowded” [sic]. However, a scaly area such as this was never observed in the C. asteroides specimens examined nor in closely related congeners. His description probably refers to the ventral surface of the terminal scute. Consequently, these two species are difficult to differentiate, and C. hige is herein regarded as a senior synonym of C. asteroides .

Relationships and comparisons. Coelorinchus hige belongs to the C. anatirostris group (see the Relationships of C. anatirostris ), and is most closely related to C. radcliffei Gilbert & Hubbs, 1920 known from the Philippines and Indonesia. The holotype of the latter species was examined here for comparison. Coelorinchus hige agrees with the holotype and the original description of C. radcliffei , with no diagnostic differences in counts and measurements, except for the internasal width (30– 35% PRL in C. hige vs. 27% in C. radcliffei ). However, according to the original description, C. radcliffei has distinctly fewer pyloric caeca (39; Gilbert & Hubbs 1920:501) as compared with C. hige (47–49; this study). Although adults of the two species are strikingly similar to each other, C. hige is easily diagnosed when young by the presence of several dark spots on the posterior part of the tail [ Fig. 21B ; vs. absent in C. radcliffei , fide Gilbert & Hubbs 1920:502]. The relatively short snout of young C. hige is also distinctive: the snout of three small specimens of C. hige (30.0–41.0 mm HL) ranged from 42 to 44% HL, whereas C. radcliffei of comparable size had a distinctively longer snout of 48% HL ( Gilbert & Hubbs 1920: unnumbered table in p. 503, fig. 22, 38.0 mm HL). Furthermore, the terminal snout scute of C. hige is shorter than that of C. radcliffei (see Gilbert & Hubbs 1920: fig. 23), although the difference is only especially prominent in small specimens. Except for the holotype, no additional specimens of C. radcliffei were examined in this study, and further investigations based on more specimens are required to verify the difference between adults of the two species.

Coelorinchus hige superficially resembles C. goobala Iwamoto & Williams, 1999 known from the eastern Indian Ocean off northwestern Australia. However, it readily differs from C. goobala in that the dorsal surface of the snout is completely scaled except for the narrow naked clefts along each side of the median rostral ridge; by contrast, the snout of C. goobala is broadly naked posterior to the lateral nasal ridges. Furthermore, the body scales of C. hige are covered with keel-like spinules that greatly overlap and closely adjoin one another to form saw-toothed ridges, whereas in C. goobala , the spinules are slender, conical, and individually separated, forming comb-like ridges. Other pronounced differences include the number of pyloric caeca (47–49 in C. hige vs. 33–44 in C. goobala ) and the coloration of the oral cavity (blackish vs. pale). Coelorinchus hige is further distinguished from C. goobala when young by the presence of dark spots on the posterior part of the tail ( Fig. 21B ) (vs. absent), and a relatively shorter scute at the tip of the snout [length of terminal snout scute 13–17% PRL (30.0– 63.4 mm HL; see also Fig. 21B ) vs. 18–33% (54.7–63.5 mm HL; see also Iwamoto & Williams 1999: fig. 11b–bʹ)].

Because of their similarity in general appearance and sympatric occurrence, in Japanese waters C. hige is most likely to be misidentified as C. anatirostris Jordan & Gilbert in Jordan & Starks, 1904. However, the two species are easily distinguished by squamation characters. In C. hige , the occipital scales are covered with short, erect, recurved, needle-like spinules in widely divergent comblike rows ( Fig. 45 E–F), whereas in C. anatirostris , spinules are keel-like and arranged in narrowly divergent rows ( Fig. 22 E–F). The absence of scales on the nasal fossa is also useful to diagnose C. hige (vs. usually heavily scaled in C. anatirostris ), although large adults of C. hige often have a few tiny scales, and also the fossa in small specimens of C. anatirostris is occasionally naked. In C. hige , scales on the median rostral ridge are covered with radiating rows of spinules, whereas in C. anatirostris , the spinules are arranged in divergent rows (the spinule rows are often irregular in small specimens of the former). The dorsal contour of the snout is almost straight in C. hige , but it is generally concave in C. anatirostris . Additionally, C. hige has significantly higher counts of pyloric caeca (47–49 vs. 21–26 in C. anatirostris ) and a relatively wider interdorsal space [51–70% PRL vs. 33–54%; second dorsal fin originating above the bases of 1st–6th anal-fin ray (usually anterior to 5th) vs. 5th–10th (usually posterior to 6th)]. Although the two species are difficult to identify in the field, C. hige is readily recognized when young by having several dark spots on the posterior part of the tail (vs. absent in C. anatirostris ; Fig. 21 ). The combination of the snout shape, the position of the second dorsal-fin origin, and the presence/absence of scales of the nasal fossa distinguishes larger specimens of the two species in the field.

Figures

FIGURE 21. Preserved juvenile specimens of two species of Coelorinchus. (A) C. anatirostris, BSKU 50891, 21.7 mm HL, 88+ mm TL, Numazu fish market, Shizuoka Pref., Pacific; (B) C. hige, BSKU 50881, 30.0 mm HL, 108+ mm HL, off Nomaike, Kagoshima Pref., East China Sea. Lateral views. [Photos: N. Nakayama]

FIGURE 22. Scanning electron micrographs showing scales of Coelorinchus anatirostris. (A–B) BSKU 4385, 98.4 mm HL; (C–F), BSKU 97958, 73.3 mm HL. (A–D) Scales from the dorsum below the interdorsal space; (E–F) from the top of the head between the parietal ridges. (A, C, E) Views from above; (B, D, F) oblique views. [Photos: N. Nakayama]

FIGURE 43. Fresh specimens of Coelorinchus hige. (A) BSKU 109039, 84.2 mm HL, 351+ mm TL, Okinawa Trough, East China Sea, 304–312 m depth; (B) BSKU 109040, 88.2 mm HL, 401+ mm TL, collected with BSKU 109039; (C–E) BSKU 112451, 72.0 mm HL, 310+ mm TL, Mimase fish market, Kochi Pref., Pacific. (A–C) Lateral views (D) dorsal and (E) ventral views of the head and trunk. [Photos: N. Nakayama]

FIGURE 44. Preserved specimen of Coelorinchus hige. FAKU 23801, holotype of Coelorhynchus asteroides, 85.5 mm HL, 376+ mm HL, Owase fish market, Mie Pref., Pacific. (A) Lateral, (B) dorsal, and (C) ventral views. [Photos: N. Nakayama]

FIGURE 45. Scanning electron micrographs showing body scales of Coelorinchus hige. (A–B) SNFR 14555, 110 mm HL; (C–F), BSKU 27032, 70.2 mm HL. (A–D) Scales from the dorsum below the interdorsal space; (E–F) from the top of the head between the parietal ridges. (A, C, E) Views from above; (B, D, F) oblique views. [Photos: N. Nakayama]