Coelorinchus matsubarai Okamura, 1982

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 105-107

Coelorinchus matsubarai Okamura, 1982

[Japanese name: Mato-hige]

( Figs. 47B , 70–71 ; Appendix 3-4C)

Coelorhynchus matsubarai Okamura, 1982:167 , fig. 101 (original description; holotype: BSKU 29440 , from Kyushu-Palau Ridge, 28º06.7ʹN, 134º39.9ʹE, in 550–600 m; 46 paratypes from Kyushu-Palau Ridge and Emperor Seamounts; new Japanese name: “Matō-hige”).

Coelorinchus matsubarai : Okamura 1984b:96, pl. 82, fig. M (compiled); Okamura 1988:96, pl. 82, fig. M (compiled); Okamura 1997:126, fig. 7 (compiled); Nakabo & Kai 2013:507 (in key; Japan); Motomura 2020:38 (listed; Japan).

Caelorinchus matsubarai : Nakabo 1993:367 (in key; Japan); Nakabo 2000:431 (in key; Japan); Nakabo 2002:431 (in key; Japan).

Diagnosis. Ventral light organ externally represented by long dark line, terminated with 1 fossa at each end, one immediately anterior to anus, the other on chest just posterior to isthmus (duct connecting each fossa often difficult to distinguish). Underside of head completely naked except along lateral nasal ridges; dorsal surface of snout almost fully scaled, naked clefts only narrowly developed along each side of median rostral ridge. Snout long, sharply pointed, length 70–88% PRL; dorsal profile of snout slightly concave in lateral view; terminal scute long, slender, spearhead-shaped, length 18–31% PRL; distal portion of snout narrowly attenuated when viewed dorsally; lateral nasal ridge incompletely supported by nasal bone. Interdorsal space less than first dorsal-fin base length. Anal fin originating posterior to vertical through second dorsal-fin origin. First dorsal fin high, but second spinous ray not especially elongate, height of fin 87–104% PRL. Second dorsal fin well developed, its rays as long as opposites of anal fin.Anus immediately anterior to anal-fin origin. Premaxillary teeth small, slender, conical in short, uniformly wide band, none especially enlarged; posterior end of tooth band falling far short of lateral corner of mouth. Body scales covered with short, reclined, needlelike spinules in subparallel to slightly divergent rows; spinules in each row almost equal in height, free from one another, with last spinule extending slightly beyond posterior scale margin; buttresses scarcely developed. Orbit diameter 44–50% PRL; postorbital length 49–56% PRL; upper-jaw length 38–46% PRL; preoral length 61– 85% PRL; barbel length 8–18% PRL. Transverse scale rows below first dorsal-fin midbase 4–6.5. Spinules on scales anterior to light organ not rudimentary. Prominent large dark blotch between lateral line and pectoralfin base; about 3 faint dark saddles on tail; fine dark vermiculations on dorsal surface of head (uniformly dark brown in preserved specimens); scale pockets on dorsal half of body outlined by dark brown; underside of head dusky, heavily peppered; lips pale; oral cavity, and gular and branchiostegal membranes blackish; first dorsal fin pale with blackish margin; pelvic fin dark, but outermost ray paler distally.

Material examined. 60 specimens. Holotype of Coelorhynchus matsubarai: BSKU 29440 (86.6 mm HL, 308+ mm TL), Kyushu-Palau Ridge , Japan, 28.1117ºN, 134.6650ºE, 550–600 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, tr. 9, bottom trawl, coll. O. Okamura et al., 19 Dec. 1979 . Paratypes of C. matsubarai: BSKU 32226 (1, 73+ mm HL, 286+ mm TL), * BSKU 32229 (1, 68+ mm HL, 277 mm TL) , * BSKU 32230 (1, 69+ mm HL, 211+ mm TL) , BSKU 32231 (1, 66+ mm HL, 259 mm TL) , BSKU 32232 (1, 71.7 mm HL, 227+ mm TL) , * BSKU 32233 (1, 65.6 mm HL, 234+ mm TL) , BSKU 32234 (1, 67.5 mm HL, 245+ mm TL) , BSKU 32235 (1, 66.6 mm HL, 266 mm TL) , BSKU 32236 (1, 62.5 mm HL, 239 mm TL) , * BSKU 32237 (1, 60.8 mm HL, 233+ mm TL) , BSKU 32238 (1, 64.0 mm HL, 242 mm TL) , BSKU 32239 (1, 64.1 mm HL, 244+ mm TL) , BSKU 32240 (1, 55.1 mm HL, 210 mm TL) , BSKU 32241 (1, 57.9 mm HL, 225+ mm TL) , BSKU 32242 (1, 53.5 mm HL, 214+ mm TL) , BSKU 32243 (1, 62.9 mm HL, 239+ mm TL) , * BSKU 32244 (1, 57.6 mm HL, 206+ mm TL) , BSKU 32245 (1, 52.8 mm HL, 201+ mm TL) , BSKU 32246 (1, 57.3 mm HL, 215+ mm TL) , BSKU 32248 (1, 55.2 mm HL, 189+ mm TL) , BSKU 32249 (1, 51.2 mm HL, 204 mm TL) , BSKU 32251 (1, 53.2 mm HL, 211 mm TL) , * BSKU 32252 (1, 56.2 mm HL, 195+ mm TL) , * BSKU 32253 (1, 50+ mm HL, 185+ mm TL) , * BSKU 32254 (1, 51.1 mm HL, 197+ mm TL) , * BSKU 32255 (1, 53.3 mm HL, 208 mm TL) , BSKU 32256 (1, 43.0 mm HL, 166+ mm TL) , BSKU 32257 (1, 41.7 mm HL, 146+ mm TL), collected with holotype ; * ZMUT KP448 (1, 62.5 mm HL, 197+ mm TL), * ZMUT KP450 (1, 43.0 mm HL, 161+ mm TL), * ZMUT KP451 (1, 68.6 mm HL, 253+ mm TL), * ZMUT KP456 (1, 66.1 mm HL, 252+ mm TL), * ZMUT KP459 (1, 64.8 mm HL, 244+ mm TL), * ZMUT KP463 (1, 53.4 mm HL, 203+ mm TL), * ZMUT KP468 (1, 54.2 mm HL, 214 mm TL), * ZMUT KP470 (1, 53.6 mm HL, 197+ mm TL), * ZMUT KP475 (1, 56.9 mm HL, 210 mm TL), * ZMUT KP478 (1, 74.6 mm HL, 285 mm TL), * ZMUT KP479 (1, 77.1 mm HL, 295 mm TL), * ZMUT KP481 (1, 58.2 mm HL, 241+ mm TL), * ZMUT KP489 (1, 64.3 mm HL, 246 mm TL), * ZMUT KP493 (1, 63.7 mm HL, 254+ mm TL), * ZMUT KP495 (1, 73.8 mm HL, 285+ mm TL), * ZMUT KP498 (1, 72.0 mm HL, 283 mm TL), * ZMUT KP596 (1, 55.2 mm HL, 209 mm TL), * ZMUT KP620 (1, 61.9 mm HL, 231+ mm TL), * ZMUT KP626 (1, 65.7 mm HL, 249 mm TL), * ZMUT KP640 (1, 59.2 mm HL, 215 mm TL), Kyushu-Palau Ridge, 28.0833ºN, 134.7000ºE, 550 m, F/ Vs Shinseimaru, No. 53 and Kyoyo-maru, No. 2, bottom trawl, coll. K. Mochizuki et al., 17 Jan. 1980 ; BSKU 29527 (1, 60.8 mm HL, 231 mm TL), BSKU 30600 (1, 54.2 mm HL, 208+ mm TL), * BSKU 30601 (1, 60.3 mm HL, 240+ mm TL), BSKU 30603 (1, 75.5 mm HL, 287+ mm TL), Kyushu-Palau Ridge, 28.0667ºN, 134.6833ºE, 523 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, tr. 14, bottom trawl, coll. O. Okamura et al., 18 Dec. 1978 .

Non-types: Japan: ZMUT KP490 (1, 61.0 mm HL, 226+ mm TL) , ZMUT KP616 (1, 42.7 mm HL, 156+ mm TL) , ZMUT KP621 (1, 52.8 mm HL, 189+ mm TL) , ZMUT KP622 (1, 62.7 mm HL, 239+ mm TL) , ZMUT KP641 (1, 48.8 mm HL, 187+ mm TL), Kyushu-Palau Ridge, date unknown ; BSKU 32237 (1, 60.4 mm HL, 234+ mm TL) , BSKU 32254 (1, 50.8 mm HL, 197+ mm TL), collected with holotype .

Counts and measurements. Based on 30 specimens (41.3–86.6 mm HL, 145+–308+ mm TL). Counts: first dorsal-fin rays II,8–10; pectoral-fin rays i16–i20; pelvicfin rays 6–7; gill rakers on first arch (outer/inner) 0/8– 10, on second arch 6–7/9; longitudinal scales 36–43; transverse scale rows below first dorsal-fin origin 5.5– 7.5, below first dorsal-fin midbase 4–6.5, below second dorsal-fin origin 5.5–7, above anal-fin origin 16.5–22.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 41–47 (70–88); orbit diameter 25–28 (44–50); postorbital length 27–33 (49–56); postrostral length 54– 60; orbit–preopercle distance 27–34 (50–58); suborbital width 12–14 (21–24); upper-jaw length 21–27 (38–46); length of rictus 17–22 (30–37); length of premaxillary tooth band 10–12 (17–21); preoral length 36–46 (61–85); length of terminal snout scute 10–17 (18–31); length of lateral nasal ridge 28–35 (48–65); length of suborbital ridge 91–97 (153–175); snout width 24–27 (42–51); internasal width 17–19 (29–35); interorbital width 20–23 (34–40); occipital width 9–11 (15–20); body width over pectoral-fin bases 30–45 (57–76); body depth at first dorsal-fin origin 43–53 (76–89); body depth at anal-fin origin 33–38 (58–68); prepelvic length 101–111 (177– 203); preanus length 140–156 (254–275); preanal length 144–163 (263–280); isthmus–pelvic distance 25–30 (46– 53); isthmus–anus distance 59–80 (107–136); isthmusanal distance 63–87 (114–149); pelvic–anal distance 40– 61 (73–105); anus–anal distance 2–8 (3–13); pelvic-fin length 33–40 (57–74); pectoral-fin length 36–45 (64–79); predorsal length 106–111 (185–202); height of first dorsal fin 48–58 (87–104); length of first dorsal-fin base 17–22 (31–38); interdorsal length 9–14 (16–24); length of gill slit 10–13 (19–23); length of posterior nostril 7–10 (11– 18); barbel length 4–10 (8–18).

Size. To at least 31 cm TL ( BSKU 29440 , holotype, 308+ mm TL).

Distribution. So far known only from the Kyushu-Palau Ridge (Appendix 3-4C) and the southern part of the Emperor Seamounts at depths of 315–600 m (Okamura 1982; Sazonov 1994; Iwamoto & Okamoto 2015). Common in its range.

Remarks. Coelorinchus matsubarai was described from 57 specimens collected from the Kyushu-Palau Ridge and the Emperor Seamounts ( Figs. 70B , 71 ). The reader can refer to the original description (Okamura 1982) for further morphological details. This species is abundant in its range, but it does not occur on the continental slope along the Pacific coasts of southern Japan.

Relationships and comparisons. Coelorinchus matsubarai belongs to the C. hubbsi group (see the Relationships of C. brevirostris ), and is most similar to C. gladius Gilbert & Cramer, 1897 confined to Hawaii and C. spilonotus Sazonov & Iwamoto, 1992 known from the Sala y Gomez Ridge and Hawaii. They are diagnosed within the group by having a prominent dark blotch between the lateral line and the pelvic-fin base, and having about 2–3 faint dark saddles on the body.

Coelorinchus matsubarai differs from C. gladius and C. spilonotus in that the spinules on the body scales are much shorter, with the last spinule in each row extending only slightly beyond the posterior scale margin ( Fig. 47B ). In contrast, the spinules of the other two species are much longer, with the tip of the last spinules extending well beyond the scale margin. The mottled color pattern of the dorsal surface of the head appears to be unique to C. matsubarai , although it is completely or almost completely faded in preserved specimens. Unfortunately, it is unknown whether the pattern is also found in C. gladius and C. spilonotus , as their fresh coloration has not been reported. Coelorinchus matsubarai is further distinguished from C. gladius by having a shorter scute at the snout tip (18–31% PRL vs. 45–52%). Due to the different size of the scute, the two species are readily distinguished by several morphometric characters, including the snout length (70–88% PRL in C. matsubarai vs. 111% in C. gladius ), preoral length (61–85% PRL vs. 104–106%), pre-dorsal length (185–202% PRL vs. 218– 222%), pre-pelvic length (117–203% PRL vs. 235%), and pre-anal length (263–280% PRL vs. 316%). Coelorinchus matsubarai also differs from C. spilonotus in that the dorsal surface of the snout is entirely scaled except for narrow naked clefts along the median rostral ridge (vs. prominent naked areas dorsally posterior to lateral nasal ridges). It is further distinguished from C. spilonotus by having a longer terminal scute (18–31% PRL vs. 15–16%) and more gill rakers [inner rakers on the first arch 8–10 vs. 5–6 in the two C. spilonotus specimens examined (6– 8 in Sazonov & Iwamoto 1992:50); inner rakers on the second arch 9 vs. 6 (6–8)]. The position of the saddles is also different between the two species. In C. matsubarai , the first saddle originates one first dorsal-fin base length posterior to the second dorsal-fin origin, and the second saddle is located well posterior to it. In C. spilonotus , the first saddle is situated anterior to the first dorsal-fin origin, and the position of the second saddle almost corresponds with that of the first of C. matsubarai (see Sazonov & Iwamoto 1992: fig. 18).

Figures

FIGURE 47. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of two species of the Coelorinchus hubbsi group. (A) C. hubbsi, BSKU 97970, 60.3 mm HL; (B) C. matsubarai, BSKU 32226, paratype, 75.5 mm HL. Views from above. [Photos: N. Nakayama]

FIGURE 70. Fresh specimens of Coelorinchus matsubarai. (A) ZMUT unknown, Kyushu-Palau Ridge, Pacific; (B) BSKU 29440, holotype, 86.6 mm HL, 308+ mm TL, Kyushu-Palau Ridge, Pacific, 550–600 m depth. Lateral views. [Photos: (A) ZMUT; (B) BSKU]

FIGURE 71. Holotype of Coelorhynchus matsubarai (= Coelorinchus matsubarai). BSKU 29440, 86.6 mm HL, 308+ mm TL, Kyushu-Palau Ridge, Pacific, 550–600 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]