Kuronezumia dara ( Gilbert & Hubbs, 1916 )

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 228-231

Kuronezumia dara ( Gilbert & Hubbs, 1916)

[Japanese name: Suruga-nezumidara]

( Figs. 150–151 , 152 A–B; Table 10 ; Appendix 3-9C)

Lionurus darus Gilbert & Hubbs, 1916:197 , pl. 10, fig. 1 [original description; holotype: USNM 76867, from “Suruga Gulf”, Albatross sta. 5060, in 197 ftm (361 m); misspelled “ durus ” in caption of pl. 10]; Okada & Matsubara 1938:453, pl. 111, fig. 2 (in key; Japan); Kuroda 1951:392 (listed; Suruga Bay; Japanese name: “Suruga-nezumidara”); Matsubara 1955:1316 (in key; Japan); Matsubara 1965:509 (compiled; Japan).

Nezumia darus: Okamura 1970a:101 [new combination; brief description after Gilbert & Hubbs (1916)]; Tominaga & Uyeno 1981:489 (listed; Japan); Okamura 1982:161, 349, fig. 95 (description; 2 spec. from Tosa Bay; photo based on BSKU 29499); Okamura 1984a:217, 363, fig. 153 (brief description; 4 spec. from Okinawa Trough; photo based on BSKU 27666); Okamura 1984b:94, pl. 81, fig. J (compiled); Okamura 1988:94, pl. 81, fig. J (compiled); Nakabo 1993:360 (in key; Japan); Okamura 1997:128, fig. 14 (compiled); Shinohara & Matsuura 1997:292 (listed; Suruga Bay); Nakabo 2000:424 (in key; Japan); Shinohara et al. 2001:306 (listed; Tosa Bay); Nakabo 2002:424 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Shinohara et al. 2005:418 (listed; Ryukyu Islands); Suetsugu & Ohta 2005: table 2 (questionable; listed; southeast of Boso Peninsula).

Nezumia dara: Okamura 1970b : table 1 (listed; Japan).

Kuronezumia dara: Shcherbachev et al. 1992:100 (new combination); Nakabo & Kai 2013:500 (in key; Japan); Iwamoto et al. 2015:82, fig. 14 (brief description; 5 spec. from southwestern Taiwan and Japan); Motomura 2020:39 (listed; Japan).

Kuronezumia darus: Shao et al. 2008b : table 2 (1 spec. from southwestern Taiwan; new Taiwanese record).

Diagnosis. A species of Kuronezumia without large, scaly, tubercular swelling anterior to anus; pelvic-fin rays 11–12; no enlarged scutes at snout tip; no open pores along cephalic sensory canals; mandibular rami scaled posteriorly; branchiostegal membranes naked; first dorsal fin uniformly black; oral cavity blackish; body scales covered with long, moderately erect, needle-like spinules densely scattered over exposed portion; first dorsal-fin rays II,9–10; pectoral-fin rays i21–i26; inner gill rakers on first arch 9–11; upper-jaw length 30–35% HL.

Material examined. 9 specimens. Holotype of Lionurus darus: USNM 76867 (19.6 mm HL, 132+ mm TL), off Fuji River , Shizuoka Pref., Suruga Bay , Japan , 35.1000ºN, 138.6694ºE, 197 ftm (361 m), Albatross sta. 5060, 9-ft Albatross-Blake beam trawl, 13 Oct. 1906. Non-types : Japan: BSKU 26326 (1, 34.5 mm HL, 210+ mm TL), off Senkaku Islands , Okinawa Trough, 25.6283ºN, 122.8933ºE, 560–692 m, F/ V Yuryo-maru, No. 8, tr. 3, bottom trawl, coll. T. Kitajima et al., 14 Jan. 1978 ; BSKU 27666 (1, 49.8 mm HL, 256+ mm TL), west of Okinawa-jima Island , Okinawa Trough, 28.7333ºN, 127.0167ºE, 610–640 m, F/ V Ryoan-maru, No. 28, tr. 49, bottom trawl, coll. Y. Kinoshita and S. Hagino, 11 Mar. 1978 ; BSKU 44828 (1, 42.0 mm HL, 220+ mm TL), Tosa Bay , 33.1755ºN, 133.6498ºE, 500 m, FRV Kotakamaru, 25 Apr. 1988 ; BSKU 45036 (1, 60.0 mm HL, 374+ mm TL), Tosa Bay , 500 m, FRV Kotaka-maru, 23 Aug. 1988 ; BSKU 30497 (1, 20.1 mm HL, 111+ mm TL), Tosa Bay , 32.9667ºN, 133.5333ºE, 605 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, bottom trawl, coll. O. Okamura et al., 21 Dec. 1979 ; BSKU 29499 (1, 21.1 mm HL, 137+ mm TL), Tosa Bay , 32.9667ºN, 133.5333ºE, 605 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, cr. 4-Ky, tr. 19, bottom trawl, coll. O. Okamura et al., 21 Dec. 1979 ; NSMT-P 48555 (1, 54.9 mm HL, 340 mm TL), southwest of Heta , Suruga Bay , 34.9517ºN, 138.7267ºE, 380–1000 m, F/ V Seishin-maru, sta. CT-1- 5, bottom trawl, 26 Oct. 1993 ; NSMT-P 101346 (1, 69.8 mm HL, 416+ mm TL), west of Matsuzaki, Suruga Bay, 34.7567ºN, 138.6650ºE, 652–676 m, R/ V Tansei-maru, cr. KT-89-06, sta. SB26, 3-m ORE beam trawl, 17 May 1989.

Redescription. General features are shown in Figs. 150–151 . Counts and measurements are given in Table 10 . Trunk deep, compressed, width over pectoral-fin bases 1.7–2.7 in depth at first dorsal-fin origin. Body deepest at first dorsal-fin origin, gradually tapering to long, well compressed tail. Head moderately large, HL about 5.1– 6.7 in TL. Supraoccipital crest moderately high, giving humpback appearance to dorsal contour of predorsal region (only in larger specimens). Snout short, protruding scarcely beyond upper jaw, length 0.7–1.1 times as long as orbit diameter; ventral contour almost vertical when viewed laterally; snout high, its tip situated on horizontal through midorbit or above. Orbit circular, moderate in size, greatest diameter 1.1–1.9 in postorbital length. Interorbital space flat or slightly concave in preserved specimens, width 1.1–1.6 in orbit diameter. Mouth small, subinferior, upper-jaw length 0.8–1.2 in orbit diameter; posterior margin of maxilla not reaching vertical through midorbit; lateral corner of mouth moderately restricted by lip folds; lips thick, highly papillose near tooth bands. Suborbital region deep, almost flat, lacking stout bony ridge. Preopercle large, posterior margin almost vertical, broadly rounded ventrally; preopercular ridge low, forming right angle posteroventrally. Interopercle narrowly exposed as narrow tab beyond preopercle. Gill membranes narrowly connected across, and attached mesially to isthmus, with posterior free fold. Anteroventral end of gill opening not reaching below posterior margin of lower jaw. Outermost gill slit moderately restricted by skin folds, length 1.5–2.2 in orbit diameter. Gill rakers small, tubercular, armed with short, slender spines distally; those on outer side of first arch and inner side of fourth arch much smaller than others. Gill filaments moderately long. Barbel long, slender, length 1.1–1.6 in orbit diameter.

Anus closer to pelvic-fin bases than to anal-fin origin. Periproct broad, more or less oval in shape. Light organ small, circular, separated from periproct by narrow scaled area; its anterior margin lying on line connecting outer pelvic-fin bases.

Teeth short, slender, sharp, in broad tapered bands in both jaws. Premaxillary teeth arranged in about 4–5 tooth rows anteriorly with outermost series significantly enlarged. Mandibular band with about 5 tooth rows at widest point near symphysis, none especially enlarged. Posterior ends of tooth bands falling far short of lateral corner of mouth in both jaws. All teeth deeply embedded in thick layer of gum papillae.

Body scales small, thin, adherent, covered with long, moderately erect, needle-like spinules densely scattered over exposed portion ( Fig. 152 A–B); tip of posteriormost spinules extending well beyond scale margin; spinules forming angle of about 45º to scale surface, giving villiform texture to body surfaces; buttresses of spinules poorly developed; reticulate structure narrowly developed on posterior parts of unexposed portion. Body fully scaled except for periproct, light organ, and fins, but pelvic fin heavily scaled proximally.

Head ridges inconspicuous, without coarsely modified scales. Terminal snout scutes absent (scales on snout tip very slightly enlarged and thickened in larger specimens); lateral angles of snout lacking coarsely modified scales. Head scales covered with short, erect, needle-like spinules in widely divergent rows.Head almost completely and uniformly scaled; naked areas confined to membrane around anterior nostril, narrow band above upper lip, and anterior half of mandibular rami; gular and branchiostegal membranes entirely naked.

Cephalic sensory canals without open pores. Grooved lateral line almost complete, often narrowly interrupted above pectoral-fin base.

First dorsal fin originating slightly posterior to vertical through pectoral-fin base; second spinous ray not especially elongate, its tip extending to base of 16th–26th second dorsal-fin ray when laid back; height of first dorsal fin 3.4– 5.3 times as long as its base length; leading edge of second spinous ray beset with short, erect, conical denticles. Second dorsal fin moderately separated from first dorsal, originating above bases of 8th–12th anal-fin rays; interdorsal space 0.8–1.5 times as long as first dorsal-fin base length. Pelvic fin inserted slightly anterior to vertical through pectoral-fin base; outermost ray greatly prolonged, its tip reaching base of 9th–15th anal-fin ray when laid back.

Color when fresh ( Fig. 150 ). Uniformly dark to dusky gray; abdomen much darker; gular and branchiostegal membranes dull black; first dorsal, pectoral, and pelvic fins uniformly black; anal fin dusky, but darker anteriorly.

Color in alcohol ( Fig. 151 ). Almost same as in fresh condition; oral cavity blackish; gums pale; gill cavity paler anteriorly, blackish posteriorly; gular membrane dusky, branchiostegal membranes black; light organ and periproct dull black.

Size. To about 42 cm TL (NSMT-P 101346, 416+ mm TL, Suruga Bay, Japan).

Distribution. Restricted to Japan and Taiwan. Known from Suruga Bay, Tosa Bay, the Okinawa Trough, and the northern South China Sea, at depths of 280‾ 1000 m ( Shcherbachev et al. 1992; Shao et al. 2008a, 2008b; Iwamoto et al. 2015; this study; Appendix 3-9C). It appears to be rare wherever found.

Remarks. Kuronezumia dara is redescribed herein based on the holotype from Suruga Bay and eight additional specimens from Japan. Although Gilbert & Hubbs (1916) originally referred this species to Lionurus G̹nther, 1887, it was subsequently transferred to Nezumia Jordan in Jordan & Starks, 1904 by Okamura (1970a), and then shifted to Kuronezumia by Sazonov & Iwamoto (1992).

Relationships and comparisons. Data used in the following comparisons are based on Shcherbachev et al. (1992) and this study. Kuronezumia dara is one of six species of the genus that is characterized by the absence of a large, scaly, bulbous swelling anterior to the anus. In this respect, K. dara is similar to the following five species: K. endoi sp. nov. from Japan; K. leonis ( Barnard, 1925) widespread in temperate to subarctic waters of the South Atlantic, Indian Ocean, and southwestern Pacific; K. macronema (Smith & Radcliffe in Radcliffe, 1912) probably restricted to the Philippines; K. paepkei Shcherbachev, Sazonov & Iwamoto, 1992 known only from the western Indian Ocean off Kenya; and K. pallida Sazonov & Iwamoto, 1992 disjunctly distributed in the Sala y Gomez Ridge in the southeastern Pacific (type locality) and the southeastern Indian Ocean off Western Australia.

Kuronezumia dara differs notably from all but K. pallida in lacking open pores along the cephalic sensory canals [vs. small but present (unknown in K. macronema )]. In addition, this species is unlikely to be confused with K. leonis as it lacks a large spiny scute at the tip of the snout (vs. present). It also differs from K. endoi , K. leonis , and K. pallida in that the gular and branchiostegal membranes are completely naked (vs. scaly patches are present on the lower portions of the branchiostegal membranes). Kuronezumia dara is further distinguished from K. paepkei by its higher counts of transverse scale rows (8.5–10.5 vs. 7 scales below the first dorsal-fin midbase; 10–11.5 vs. 8 scales below the second dorsal-fin origin) and lower counts of gill rakers (9–11 vs. 12 on the inner side of the first arch; 8–10 vs. 11 on the outer side of the second arch).

As discussed by Shcherbachev et al. (1992:102), K. dara is most similar to K. macronema , and they are difficult to distinguish by meristic and morphometric characters ( Shcherbachev et al. 1992: table 1). According to the key to species given by Shcherbachev et al. (1992), K. dara is distinguished from K. macronema in having a uniformly black first dorsal fin (vs. darker basally and paler distally). Unfortunately, the present author had no opportunity to examine specimens of the latter species, and their differences should be verified in the future.

Figures

FIGURE 150. Fresh specimens of Kuronezumia dara. (A) BSKU 29499, 21.1 mm HL, 137+ mm TL, Tosa Bay, Kochi Pref., Pacific, 605 m depth; (B) BSKU 44828, 42.0 mm HL, 220+ mm TL, Tosa Bay, Kochi Pref., Pacific, 500 m depth; (C) BSKU 45036, 60.0 mm HL, 374+ mm TL, Tosa Bay, Kochi Pref., Pacific, 500 m depth. Lateral views. [Photos: BSKU]

FIGURE 151. Holotype of Lionurus darus (= Kuronezumia dara). USNM 76867, 19.6 mm HL, 132+ mm TL, Suruga Bay, Shizuoka Pref., Pacific, 361 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]

FIGURE 152. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of two species of Kuronezumia. (A–B) K. dara, BSKU 45036, 60.0 mm HL; (C–D) K. endoi sp. nov., MSM 71-945, holotype, 32.7 mm HL. (A, C) Views from above; (B, D) oblique views. [Photos: (A–B) N. Nakayama; (C–D) NSMT]