Coryphaenoides microps (Smith & Radcliffe

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 190-192

Coryphaenoides microps (Smith & Radcliffe in Radcliffe, 1912)

[No Japanese name]

( Figs. 122 C–D, 123–124; Appendix 3-7A)

Macrourus microps Smith & Radcliffe in Radcliffe, 1912:116, pl. 25, fig. 2 [original description; holotype: USNM 72933 , from Atulayan Island, eastern coast of Luzon Island, Albatross sta. 5470, 13º37ʹ30ʺN, 123º41ʹ09ʺE, in 560 ftm (1024 m); 4 paratypes from northern Luzon] .

Coryphaenoides marginatus (not Steindachner & D̂derlein 1887): Shao 1993:171 (compiled; Taiwan); Shao et al. 2008b: table 2 (36 spec. listed from northeastern, southeastern and southwestern Taiwan, and South China Sea).

Coryphaenoides microps: Chiou et al. 2004a : table 1 (listed; Taiwan); Shao et al. 2008b: table 2 [1 spec. listed from southwestern Taiwan (as first Taiwanese record)]; Kim et al. 2009b:108, fig. 3 [brief description; 14 spec. from Korea, Taiwan, and Philippines (including holotype); new Korean record from Korea]; Iwamoto et al. 2015:70 (brief description; 53 spec. from northeastern and southwestern Taiwan, and Philippines).

Diagnosis. Pelvic-fin rays 7–8. Snout short, slightly protruding beyond upper jaw. Tip and lateral angles of snout armed with stout tubercles; scales along head ridges not coarsely modified. Mouth small, posterior margin of upper jaw not reaching vertical through midorbit; upper-jaw length 30–31% HL; lateral corner of mouth moderately restricted by skin folds. Outermost gill slit greatly restricted, length 4–7% HL. Barbel short, slender, length 5–10% HL. Teeth all small, conical, slender in wide bands in both jaws, none especially enlarged. Body scales covered with short, greatly reclined, needle-like spinules in tightly packed subparallel rows; tip of last spinule in each row extending distinctly beyond posterior scale margin. Transverse scale rows. Top of snout fully scaled; underside of snout narrowly naked above upper lip. Second spinous ray of first dorsal fin notably prolonged, height of first dorsal fin distinctly greater than HL (198– 300% HL); serration along its leading edge rudimentary in adults; first dorsal-fin rays. Pelvic-fin bases closer together, their interspace less than base length of each fin. Body dusky brown overall.

Material examined. 5 specimens. Taiwan: ASIZP 66413 (1, 43.7 mm HL, 241+ mm TL), Dong-gang fish market, Pingtung, bottom trawl, coll. P.-F. Lee, 7 Oct. 2005 ; ASIZP 63792 (1, 78.5 mm HL, 367+ mm TL), off Kaohsiung, 22.3667ºN, 120.1000ºE, 821 m, otter trawl, coll. H.-M. Yeh, 29 Aug. 2002 ; ASIZP 66099 (1, 52.4 mm HL, 298 mm TL), ASIZP 66109 (1, 80.4 mm HL, 324+ mm TL), off Kaohsiung, 22.3333ºN, 120.1000ºE, 687 m, ORE-type beam trawl, coll. P.-F. Lee, 11 Aug. 2005; * FAKU 204442 (1, 37.0 mm HL, 201+ mm TL) , Dong-gang fish market, Pingtung, bottom trawl, coll. N. Nakayama, 27 Feb. 2017 .

Counts and measurements. Based on 4 specimens (43.7–80.4 mm HL, 241+–367+ mm TL). Counts: first dorsal-fin rays II,9–10; pectoral-fin rays i19–i21; pelvicfin rays 7–8; gill rakers on first arch (outer/inner) 4–5/9– 10, on second arch 9–10/8–9; longitudinal scales 33–41; transverse scale rows below first dorsal-fin origin 10– 11, below first dorsal-fin midbase 7.5–9, below second dorsal-fin origin 7–8.5, above anal-fin origin 25–28.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 28–30 (38–42); orbit diameter 19–22 (26–31); postorbital length 50–55 (70–74); postrostral length 71– 74; orbit–preopercle distance 41–46 (57–63); suborbital width 12–14 (17–20); upper-jaw length 30–31 (42–43); length of rictus 21–23 (29–31); length of premaxillary tooth band 18–20 (26–27); preoral length 11–14 (16–20); distance between tip and lateral angle of snout 12–16 (17–22); snout width 21–25 (28–35); internasal width 15–17 (21–23); interorbital width 18–21 (24–29); body width over pectoral-fin bases 44–58 (62–81); body depth at first dorsal-fin origin 78–86 (109–121); body depth at anal-fin origin 70–83 (98–116); prepelvic length 118–134 (165–182); preanus length 172–179 (241–244); preanal length 177–187 (248–254); isthmus–pelvic distance 43– 46 (60–62); isthmus–anus distance 89–101 (124–141); isthmus–anal distance 94–107 (131–150); pelvic–anal distance 55–65 (77–91); pelvic-fin length 53–62 (75– 84); pectoral-fin length 64–68 (90–92); predorsal length 117–124 (165–174); height of first dorsal fin 198–300 (269–421); length of first dorsal-fin base 27–29 (37–41); interdorsal length 12–24 (17–33); length of gill slit 4–7 (5–9); length of posterior nostril 6–8 (9–11); barbel length 5–10 (7–14).

Size. Attains at least 46 cm TL (ASIZP 66111, 464+ mm TL, South China Sea; see Iwamoto et al. 2015:70).

Distribution. Known from the Philippines, Taiwan, and Korea, at depths of 115–1165 m ( Radcliffe 1912; Shcherbachev & Iwamoto 1995; Shao et al. 2008a, 2008b). No specimens have been collected from Japanese waters (Appendix 3-7A). Common in Taiwan.

Remarks. For a full description see Shcherbachev & Iwamoto (1995). Coryphaenoides microps appears to be a sister species to C. marginatus Steindachner & D̂derlein, 1887 known from Japan and Korea. The two species are parapatric, with their distributions only slightly overlapping in the Sea of Japan off Korea (Appendix 3-6F and 3-7A).

Relationships and comparisons. Coryphaenoides microps belongs to the C. marginatus group (see the Relationships of C. marginatus ), and is most similar to C. marginatus . However, C. microps readily differs from C. marginatus in that the spinules on the body scales are arranged in tightly packed, narrowly convergent rows (vs. tightly packed parallel rows), with the tip of the last spinule in each row extending distinctly beyond the posterior scale margin (vs. scarcely reaching this level) ( Fig. 122 C–D vs. A–B). Coryphaenoides microps further differs from that species in having a smaller orbit (19–22% HL vs. 22–31%) and a longer postorbital (50–55% HL vs. 42–51%). In the four C. microps specimens examined, the underside of the head was almost fully scaled along the infraorbital, preopercular, and mandibular canals, and naked areas were apparent only on anterior portions of the mandibular rami and a narrow band above the upper lip. In contrast, the C. marginatus specimens examined had broad naked areas above the upper lip and along margins of the interopercle, preopercle, and mandibular rami. Coryphaenoides microps is unlikely to be confused with females of C. marginatus by having a uniformly dark body (vs. paler ventrally) and blackish fins (vs. first dorsal and pelvic fins pale except for dark distal margins).

Figures

FIGURE 122. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of three species of the Coryphaenoides marginatus group. (A–B) C. marginatus, BSKU 103048, 71.4 mm HL; (C–D) C. microps, ASIZP 66413, 43.7 mm HL; (E–F) C. nasutus, BSKU 103042, 78.5 mm HL. (A, C, E) Views from above; (B, D, F) oblique views. [Photos: NSMT]