Trachonurus villosus (Günther, 1877)

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 281-284

Trachonurus villosus (Günther, 1877)

[Japanese name: Wata-hige]

( Figs. 193–195 ; Appendix 3-12B)

Coryphaenoides villosus G̹nther, 1877:441 [original description; holotype: BMNH 1887.12 .7.105, from “south of Yeddo ” (off Eno-shima Island), Challenger sta. 232, in 345 ftm (631 m)] .

Macrurus villosus : G̹nther 1887:142–143, pl. XXXVI, fig. B [description; in part, 1 spec., BMNH 1887.12 .7.105 (holotype); remaining 1 spec. probably represents different species (fide Iwamoto 1997:945)] .

Trachonurus villosus : Jordan & Snyder 1901:120 (listed; Japan); Jordan & Gilbert in Jordan & Starks 1904:621 [after G̹nther (1877, 1887)]; Jordan et al. 1913:420 (listed; Japan; new Japanese name: “Wata-hige”); Gilbert & Hubbs 1916:205 (description; 4 spec. from off Cape Shionomisaki and southsouthwest of Izu Island); Kamohara 1931b:544 (questionable; listed; Kochi); Kamohara 1934a:54 (questionable; listed; Kochi); Okada & Matsubara 1938:453 (in key; Japan); Kamohara 1938:73 (questionable; spec. from Kochi Pref.); Kamohara 1950:279 (questionable; listed; Kochi Pref.); Kamohara 1952:99 (questionable; spec. from Kochi Pref.); Matsubara 1955:1317 (in key; Japan); Kamohara 1958:74 (questionable; listed; Kochi Pref.); Kamohara 1964:96 (questionable; listed; Kochi Pref.); Okamura 1970a:106, pl. XXIII, text-fig. 44 (description; 1 spec. from East China Sea); Okamura 1970b: table 1 (listed; Japan); Tominaga & Uyeno 1981:489 (listed; Japan); Okamura 1984b:94, pl. 81, fig. L (compiled); Okamura 1988:94, pl. 81, fig. L (compiled); Sazonov & Iwamoto 1992:77 (unnecessary lectotype designation; synonymy; comments on Challenger spec.; 2 additional spec. from Sala y Gomez Ridge); Nakabo 1993:356 (in key; Japan); Okamura 1997:128, fig. 7 (compiled); Nakabo 2000:420 (in key; Japan); Shinohara et al. 2001:306 (listed; Tosa Bay); Nakabo 2002:420 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Shinohara et al. 2005:418 (listed; Ryukyu Islands); Shao et al. 2008b: table 2 (5 spec. listed from South China Sea); Nakabo & Kai 2013:496 (in key; Japan); Iwamoto et al. 2015:104, fig. 26 (brief description; 4 spec. from southwestern Taiwan and South China Sea); Motomura 2020:39 (listed; Japan).

Diagnosis. A species of Trachonurus with grooved lateral line; pelvic-fin rays 7; gular and lower portions of branchiostegal membranes heavily scaled; outer series of premaxillary tooth band distinctly enlarged; pectoralfin rays i13–i17 (usually i15); inner gill rakers on first arch 10–12; body scales small, longitudinal scales 32–46; scales below first dorsal-fin midbase 4.5–8, below second dorsal-fin origin 5–9.

Material examined. 10 specimens. Holotype of Coryphaenoides villosus : * BMNH 1887.12 .7.105 (26.0 mm HL, 193+ mm TL), off Eno-shima Island , Kanagawa Pref., Sagami Bay, Japan, 35.1833ºN, 139.4667ºE, 345 ftm (631 m), Challenger sta. 232, trawl and dredge, 12 Mar. 1875 (only photographed and briefly examined in this study). Non-types: Japan: BSKU 26555 (1, 25.8 mm HL, 114+ mm TL), off Miyako-jima Island, Okinawa Trough , 26.4633ºN, 124.8483ºE, 680–770 m, F/ V Yuryomaru, No. 8, tr. 10, bottom trawl, coll. S. Kishida and Y. Kinoshita, 23 Jan. 1978 ; NSMT-P 93826 (1, 57.7 mm HL, 362+ mm TL), northern Okinawa Trough , 917–919 m, R/ V Tansei-maru, cr. KT-93-09, 3-m beam trawl, 18 Jun. 1877 ; BSKU 23083 (1, 45.2 mm HL, 290+ mm TL), off Kochi, 32.9800ºN, 133.8550ºE, 1043 m, FRV Kaiyomaru, cr. SK-75-2, sta. 9, tr. 2, bottom trawl, 26 Jan. 1975 ; BSKU 23055 (1, 60.1 mm HL, 383+ mm TL), Tosa Bay , 33.0350ºN, 133.7500ºE, 945 m, FRV Kaiyo-maru, cr. SK-75-2, sta. 18, tr. 3, bottom trawl, 26 Jan. 1975 ; SNFR uncat. (1, 56.3 mm HL, 328+ mm TL), Tosa Bay , 750 m, FRV Kotaka-maru, otter trawl, 13 Sept. 1988 ; BSKU 43458 (1, 79.7 mm HL, 463+ mm TL), south-southwest of Okinoshima Island , 32.5450ºN, 132.4750ºE, 1075–1092 m, R/ V Tansei-maru, cr. KT-86-16, sta. C, 3-m beam trawl, 2 Nov. 1986 ; BSKU 20536 (1, 37.2 mm HL, 229+ mm TL), south of Izu Peninsula , 34.3333ºN, 138.8167ºE, FRV Soyo-maru, sta. 30, 5 Oct. 1965 ; HUMZ 71882 (1, 124 mm HL, 495+ mm TL) , HUMZ 71883 (1, 110 mm HL, 675+ mm TL), off Minami-torishima Island , 23.8667ºN, 150.6667ºE, 10 Oct. 1977 .

Counts and measurements. Based on 9 specimens (25.8–124 mm HL, 114–675 mm TL). Counts: first dorsal-fin rays II,7–9; pectoral-fin rays i13–i17; pelvic-fin rays 7; gill rakers on first arch (outer/inner) 4–9/10–12, on second arch 9–14/10–12; longitudinal scales 32–46; transverse scale rows below first dorsal-fin origin 6.5– 8.5, below first dorsal-fin midbase 4.5–8, below second dorsal-fin origin 5–9, above anal-fin origin 22–33.5.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 24–29 (31–40); orbit diameter 24–33 (32–42); postorbital length 46–55 (60–71); postrostral length 73–79 (–); orbit–preopercle distance 30–39 (39–51); suborbital width 10–14 (14–18); upper-jaw length 31– 38 (41–49); length of rictus 26–33 (35–42); length of premaxillary tooth band 20–26 (26–34); preoral length 12–16 (16–21); distance between tip and lateral angle of snout 10–16 (13–21); snout width 18–24 (23–31); internasal width 19–23 (25–32); interorbital width 32– 38 (43–51); body width over pectoral-fin bases 38–66 (50–90); body depth at first dorsal-fin origin 66–104 (89–135); body depth at anal-fin origin 52–93 (68–119); prepelvic length 114–134 (149–181); preanus length 137–165 (180–214); preanal length 144–172 (189–230); isthmus–pelvic distance 55–65 (72–88); isthmus–anus distance 74–95 (98–123); isthmus–anal distance 82–108 (108–140); pelvic–anal distance 26–46 (34–58); anusanal distance 8–15 (10–20); pelvic-fin length 29–45 (38–60); pectoral-fin length 42–54 (56–71); predorsal length 109–121 (143–164); height of first dorsal fin 51– 65 (67–87); length of first dorsal-fin base 16–23 (21–32); interdorsal length 27–45 (36–61); length of gill slit 14–20 (19–25); length of posterior nostril 5–10 (7–14); barbel length 9–12 (11–16).

Size. Attains about 68 cm TL ( HUMZ 71883, 675 mm TL, off Minami-torishima Island, Japan).

Distribution. RecordedfromthenorthwesternPacific off Japan and Taiwan as well as from the southeastern Pacific at the Sala y Gomez Ridge; depth range 514–1240 m ( Sazonov & Iwamoto 1992; Shao et al. 2008a, 2008b; this study). In Japanese waters, known from the Pacific off southern Japan northward to the Miura Peninsula (139.62ºE), Okinawa Trough, and off Minami-torishima Island, at depths of 631‾ 1187 m (Appendix 3-12B). It appears to be rare wherever found.

Comments on type specimen. G̹nther (1877) originally described the species (as Coryphaenoides villosus ) based on a single small specimen (BMNH 1887.12.7.105, 26 mm HL, 193+ mm TL; Fig. 194 ) collected from “south of Yeddo”, Japan. Ten years after the original description, he (1887) reported an additional specimen from the south of the Philippines (BMNH 1887.12.7.106, 45 mm HL, 246+ mm TL). Sazonov & Iwamoto(1992:78) erroneously considered the Philippines specimen as a syntype of T. villosus , designating the Japanese specimen as the lectotype of this species.This act was probably due to their recognition that the Philippines specimen “appears to be a different species with a longer upper jaw, longer barbel, longer first gill slit, wider 1D.– 2D. interspace, and larger scales”. According to Iwamoto (1997:945), this specimen is unable to be allocated to any known species, partly owing to its poor condition. The above Philippines specimen is not included in the type series of T. villosus , being designated as a paralectotype of Coryphaenoides asper in this study (see the Comments on type specimens of C. asper ).

Remarks. Sazonov & Iwamoto (1992) reported T. villosus from the Sala y Gomez Ridge in the southeastern Pacific, but noted that their specimens differ from the holotype from Japan in many aspects, including the orbit diameter, suborbital width, orbit–preopercle distance, upper-jaw length, and the number of pelvic-fin rays. A further study is required to confirm the conspecificity of these two populations.

Comparisons. The species of Trachonurus are very similar to each other in general appearance, with most species having few diagnostic features that allow ready identification (Iwamoto 1997:942). Among the other five species of the genus (see the Remarks of the genus), T. gagates Iwamoto & McMillan, 1997 may not be confused with any other congeners in the absence of a grooved lateral line on the body (vs. present).However, the remaining four species are quite similar to T. villosus , and they are most likely to be misidentified without a detailed examination of morphology. Based on published information, T. villosus differs from T. sentipellis Gilbert & Cramer, 1897 in that the outer premaxillary teeth are distinctly enlarged (vs. scarcely or not at all enlarged, fide Iwamoto & Williams 1999:213), and from T. robinsi Iwamoto, 1997 in having fewer spinules on the body scales (see Iwamoto 1997: fig. 2). According to Iwamoto (1997:948), T. villosus can be distinguished from T. sulcatus ( Goode & Bean, 1885) in its slightly lower dimensions of the upper-jaw length, suborbital width, and snout length. However, these differences become negligible when considering variation of the T. villosus specimens examined in this study. The differences between T. villosus and T. yiwardaus Iwamoto & Williams, 1999 were not discussed in the original description of the latter ( Iwamoto & Williams 1999), and should be confirmed by a direct comparison of the two species in the future. As noted by Iwamoto (1997:948), there remains much work to be done on Trachonurus , and additional characters are obviously necessary to further characterize each species. A molecular approach may be helpful to clarify the problems within this difficult group of grenadiers.

Figures

FIGURE 193. Fresh specimens of Trachonurus villosus. (A) BSKU 23083, 45.2 mm HL, 290+ mm TL, off Kochi, Kochi Pref., Pacific, 1043 m depth; (B) BSKU 43458, 79.7 mm HL, 463+ mm TL, south-southwest of Okino-shima Island, Kochi Pref., Pacific, 1075–1092 m depth; (C) HUMZ 71883, 110 mm HL, 675+ mm TL, off Minami-torishima Island, Pacific. Lateral views. [Photos: (A–B) BSKU; (C) HUMZ]

FIGURE 194. Holotype of Coryphaenoides villosus (= Trachonurus villosus). BMNH 1887.12.7.105, 26.0 mm HL, 193+ mm TL, Sagami Bay, Pacific, 631 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and body. [Photos: N. Nakayama]

FIGURE 195. Scanning electron micrographs showing a body scale (from the dorsum below the interdorsal space) of Trachonurus villosus. BSKU 43458, 79.7 mm HL. (A) View from above; (B) oblique view. [Photos: N. Nakayama]