Hymenocephalus striatissimus Jordan & Gilbert

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 218-221

Hymenocephalus striatissimus Jordan & Gilbert in Jordan & Starks, 1904

[Japanese name: Sujidara]

( Figs. 143–145 ; Appendix 3-8E)

Hymenocephalus striatissimus Jordan & Gilbert in Jordan & Starks, 1904:612, unnumbered fig. [original description; holotype: USNM 50934, from Suruga Bay, Albatross sta. 3738, in 167 ftm (306 m); 3 paratypes from Suruga Bay]; Jordan et al. 1913:411, fig. 381 (listed; Japan; new Japanese name: “Suji-dara”); Gilbert & Hubbs 1916:187 (brief description; 15 spec. from East China Sea, off Cape Shionomisaki, and Suruga Bay); Izuka & Matsuura 1920:103 (spec. from “ Tōkyō Market”); Okada & Matsubara 1938:451 (in key; Japan); Kamohara 1950:277 (listed; Kochi and Wakayama Pref.); Kuroda 1951:392 (listed; Suruga Bay); Uchinomi 1951:76 (listed; southern part of Kii Peninsula); Kamohara 1952:96 (brief description; Kochi Pref.); Matsubara 1955:1315 (in key; Japan); Kobayashi 1956:72 (listed; Enshu-nada); Kamohara 1958:74 (listed; Kochi Pref.); Kamohara & Okamura 1958:32, pl. 31, fig. 151 (compiled; Japan); Okada et al. 1959:83 (listed; Kumano-nada); Kamohara 1964:96 (listed; Kochi Pref.); Tatara et al. 1965:121 (listed; off Shikoku); Matsubara 1965:507 (compiled; Japan); Yatou 1982:143, 346, fig. 86 [brief description; 7 spec. from Kyushu-Palau Ridge and Tosa Bay; photo based on BSKU spec. (catalog no. unknown)]; Ohta 1983: table A (listed; Suruga Bay); Ozawa 1983:13 (listed; off Makurazaki, Kagoshima Pref., East China Sea); Okamura 1984a:199, 358 [brief description; 25 spec. from Okinawa Trough; photo based on BSKU 36798 (from Mimase fish market)]; Okamura 1984b:92, pl. 80, fig. E (compiled); Okamura 1988:92, pl. 80, fig. E (compiled); Nakabo 1993:355 (in key; Japan); Shao 1993:171 (compiled; Taiwan); Shinohara et al. 1996:169 (5 spec. listed from Pacific off Tohoku); Okamura 1997:128, fig. 3 [compiled; photo spec. is H. lethonemus (BSKU 41914)]; Shinohara & Matsuura 1997:291 (listed; Suruga Bay); Nakabo 2000:419 (in key; Japan); Shinohara et al. 2001:305 (667 spec. listed from Tosa Bay); Nakabo 2002:419 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Nakajima 2003:53 (brief description; 1 spec. from Enshu-nada); Chiou et al. 2004a: table 1 (listed; Taiwan); Shinohara et al. 2005:417 (listed; Ryukyu Islands); Kitagawa et al. 2008:38, unnumbered fig. (brief description; spec. from Pacific off Tohoku); Shinohara et al. 2009:708 (listed; Pacific off Tohoku); Furuhashi et al. 2010: table 2 (49 spec. listed from northern Okinawa Trough); Nakabo & Kai 2013:495 (in key; Japan); Schwarzhans 2014:60, fig. 32 (description; comparison; in key); Iwatsuki et al. 2017:32 (listed; Hyuga-nada); Motomura 2020:39 (listed; Japan).

Hymenocephalus striatissimus striatissimus: Chen 1951:210 (listed; Taiwan); Okamura 1970a:48, pl. XV (description; biological notes; 90 spec. from Pacific off southern Japan from Suruga Bay to Totoro and East China Sea); Okamura 1970b: table 1 (listed; Japan); Kataoka & Tomida 1981:78 (listed; Mie Pref.); Tominaga & Uyeno 1981:489 (listed; Japan); Ohta 1983: table B (listed; Suruga Bay); Akazaki 1984:265 (listed; Aoshima, Miyazaki Pref.); Suetsugu & Ohta 2005: tables 2–3 (listed; southeast of Boso Peninsula and Enshu-nada); Shao et al. 2008b: table 2 (34 spec. listed from northeastern and eastern Taiwan, and South China Sea); Iwamoto et al. 2015:77 (brief description; 42 spec. from northeastern and eastern Taiwan, and South China Sea).

Diagnosis. A species of Hymenocephalus with 8 or 9 pelvic-fin rays; barbel moderately short, length 14–23% PRL, its tip not reaching vertical through hind margin of orbit when depressed; snout high, not depressed, length 26–37% PRL; orbit diameter 48–59% PRL; interorbital width 32–40% PRL; first dorsal-fin rays II,8–10; pectoral-fin rays i11–i16; gill rakers on first arch (outer/ inner) 12–18/20–24, on second arch 19–23/16–23; dorsal surface of trunk prominently blackish below first dorsalfin base; the dark area on dorsum trunk followed by faint dusky stripe forming clusters of small melanophores; lower half of tail lacking black pigmentation; body flesh translucent posteriorly on tail (only when fresh) where caudal vertebrae visible from outside; ostial and caudal colliculi of otolith fused.

Material examined. 32 specimens. Holotype of Hymenocephalus striatissimus: USNM 50934 (currently comprising 2 spec., 16.7–17.7 mm HL, 99+–112+ mm TL, 1 of which is holotype), off Heta, Shizuoka Pref., Suruga Bay, Japan , 34.9667ºN, 138.7667ºE, 167 ftm (306 m), Albatross sta. 3738, 8-ft Tanner beam trawl, 17 Mar. 1900 . Paratype of H. striatissimus: CAS-SU 8549 (1, 23+ mm HL, 113+ mm TL), Suruga Bay , Albatross sta. 3721 or 3738, 8-ft Tanner beam trawl, Mar. 1900 . Nontypes : Japan : BSKU 26290 (1, 32.8 mm HL, 148+ mm TL), off Senkaku Islands, Okinawa Trough , 24.6833ºN, 122.5933ºE, 510–615 m, F/ V Yuryo-maru, No. 8, tr. 2, bottom trawl, coll. T. Kitajima et al., 13 Jan. 1978 ; BSKU 77294 (1, 29.7 mm HL, 170+ mm TL), south of Muroto , 33.0790ºN, 134.1645ºE, 414–513 m, R/ V Tansei-maru, cr. KT-05-29, sta. K-500, 3-m ORE beam trawl, coll. H. Endo et al., 17 Nov. 2005 ; BSKU 98924 (1, 32.6 mm HL, 201+ mm TL) , BSKU 98931 (1, 35.8 mm HL, 213+ mm TL), Tosa Bay , 33.1428ºN, 133.6248ºE, 450–490 m, FRV Kotaka-maru, otter trawl, 1 Aug. 1988 ; BSKU 12934 (1, 31.1 mm HL, 187+ mm TL), Tosa Bay , 350–450 m, bottom trawl, 14 May 1968 ; BSKU 41903 (1, 32.7 mm HL, 199+ mm TL) , BSKU 41904 (1, 35.1 mm HL, 217+ mm TL) , BSKU 41906 (1, 33.5 mm HL, 204+ mm TL) , BSKU 41909 (1, 32.7 mm HL, 189+ mm TL), Tosa Bay , 420–450 m, FRV Kotaka-maru, otter trawl, 6 Jun. 1985 ; BSKU 58543 (1, 29.8 mm HL, 191 mm TL), Mimase fish market, bottom trawl, 1 Feb. 2002 ; BSKU 70088 (1, 16.2 mm HL, 67+ mm TL), Mimase fish market, bottom trawl, 15 Jan. 2004 ; BSKU 53083 (1, 26.8 mm HL, 174+ mm TL), Mimase fish market, bottom trawl, 18 Dec. 2000 ; BSKU 58427 (1, 27.1 mm HL, 160+ mm TL), Mimase fish market, bottom trawl, 3 Dec. 2001 ; BSKU 78828 (1, 28.4 mm HL, 170+ mm TL), Mimase fish market, bottom trawl, 6 Apr. 2006 ; * BSKU 92222 (1, ca. 157 mm TL), Mimase fish market, F/ V Seiryo-maru, bottom trawl, coll. N. Nakayama, 7 Nov. 2007 ; BSKU 94814 (1, 23.7 mm HL, 161 mm TL) , BSKU 94815 (1, 19.0 mm HL, 92+ mm TL), Mimase fish market, F/ V Kosei-maru, bottom trawl, 28 Nov. 2007 ; BSKU 112461 (1, 22.6 mm HL, 150 mm TL) , BSKU 112462 (1, 21.9 mm HL, 118+ mm TL), off Susaki, Tosa Bay , 320–380 m, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama et al., 9 Mar. 2014 ; BSKU 113966 (1, 29.0 mm HL, 159+ mm TL), off Susaki, Tosa Bay , 350–365 m, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama et al., 23 Apr. 2014 ; BSKU 112514 (1, 21.6 mm HL) , BSKU 112517 (1, 24.6 mm HL, 160+ mm TL) , BSKU 113656 (1, 23.1 mm HL, 145+ mm TL) , BSKU 113658 (1, 21.3 mm HL, 138+ mm TL) , BSKU 113659 (1, 26.3 mm HL, 153+ mm TL) , BSKU 113660 (1, 20.3 mm HL, 132+ mm TL), off Okitsu, Tosa Bay , 380 m, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama et al., 11 Mar. 2014 ; * BSKU 43410 (1, 31.3 mm HL, 206+ mm TL) , BSKU 43412 (1, 29.4 mm HL, 133+ mm TL), south of Okino-shima Island , 32.6400ºN, 132.5367ºE, 440–451 m, R/ V Tansei-maru, cr. KT-86-16, sta. A-3, 2-m beam trawl, 1 Nov. 1986 ; BSKU 113665 (1, 27.3 mm HL, 174+ mm TL), Numazu fish market, coll. S. Ohashi and M. Takami, 16 Feb. 2010 .

Counts and measurements. Based on 30 specimens (16.2–35.8 mm HL, 67+–217+ mm TL). Counts: first dorsal-fin rays II,8–10; pectoral-fin rays i11–i16; pelvicfin rays 8–9; gill rakers on first arch (outer/inner) 12– 18/20–24, on second arch 19–23/16–23; longitudinal scales 16–19; transverse scale rows below first dorsal-fin origin 2.5–4.5, below first dorsal-fin midbase 2–3, below second dorsal-fin origin 2–3, above anal-fin origin 5–8.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 21–28 (26–37); orbit diameter 39–46 (48–59); postorbital length 43–47 (52–57); postrostral length 75–83; orbit–preopercle distance 38–46 (47–59); suborbital width 10–12 (12–15); upper-jaw length 49–55 (62–67); length of rictus 43–47 (52–59); length of premaxillary tooth band 38–45 (47–57); preoral length 11–18 (14–22); distance between tip and lateral angle of snout 14–20 (17–25); snout width 27–31 (33–40); internasal width 17–25 (21–33); interorbital width 26–34 (32–40); occipital width 8–13 (10–16); body width over pectoral-fin bases 38–60 (47–77); body depth at first dorsal-fin origin 57–87 (69–107); body depth at anal-fin origin 43–56 (53–72); prepelvic length 99–118 (123–153); preanus length 167 (201); preanal length 151– 175 (185–221); isthmus–pelvic distance 46–63 (55–79); isthmus–anal distance 107–131 (134–163); pelvic–anal distance 53–76 (65–96); pelvic-fin length 57–70 (70–90); pectoral-fin length 51–74 (61–92); predorsal length 99–110 (121–145); height of first dorsal fin 64–95 (79–114); length of first dorsal-fin base 29–36 (36–46); interdorsal length 66–95 (81–119); length of gill slit 29–36 (35–43); length of posterior nostril 3–6 (3–8); barbel length 11–18 (14–23).

Size. To about 22 cm TL (BSKU 41904, 217+ mm TL, Tosa Bay, Japan).

Distribution. Known from the Pacific off Japan northward to Iwaki (37.07ºN, Fukushima Pref.), Kyushu-Palau Ridge, East China Sea northward to Tsushima Island, and northern South China Sea ( Shao et al. 2008a, 2008b; Schwarzhans 2014; Iwamoto et al. 2015; this study; Appendix 3-8E). Schwarzhans (2014:60) also recorded the species from the Philippines based on a single specimen collected from off Jolo Island (ZMUC P375860). Depth range varies from 150 to 1188 m, but usually shallower than 500 m. Very abundant on the upper continental slope off southern Japan.

Remarks. For further morphological details see the original description ( Jordan & Gilbert in Jordan & Starks 1904) and a redescription given by Okamura (1970a); otolith morphology was fully described by Schwarzhans (2014).

Gilbert & Hubbs (1920) recognized three subspecies under H. striatissimus , viz., H. s. aeger Gilbert & Hubbs, 1920 , H. s. striatissimus , and H. s. torvus Smith & Radcliffe in Radcliffe, 1912. Subsequently, Okamura (1970a) described a fourth subspecies, H. s. hachijoensis . All these taxa currently deserve full species status ( Schwarzhans 2014).

Comments on type specimens. Hymenocephalus striatissimus was described from three specimens collected from Suruga Bay . In the original description, Jordan & Gilbert (in Jordan & Starks 1904) designated a 108 mm long specimen as the holotype, giving the catalog number as USNM 50934 . However , this lot currently contains two specimens of about equal size (16.7–17.7 mm HL, 99+–112+ mm TL; Fig. 144 ), and it is uncertain which specimen represents the holotype.

Relationships and comparisons. Hymenocephalus striatissimus belongs to the H. striatissimus group as defined by Schwarzhans (2014). The other members of this group are: H. aeger known from Indonesia, Papua New Guinea, and off Western Australia; H. megalops Iwamoto & Merrett, 1997 distributed in the New Caledonian region and off Queensland; and H. torvus probably endemic to the Philippines. According to Schwarzhans (2014), H. striatissimus differs primarily from H. aeger in having a shorter barbel [15–20% HL (11–18% in the specimens examined in this study) vs. 20–25%]; from H. megalops in having a smaller orbit [37–42% HL (39–46%) vs. 41– 45%]; and from H. torvus in its higher counts of pelvic-fin rays [8 (8–9) vs. 7]. See Schwarzhans (2014) for further comparisons of these four species.

McMillan & Iwamoto (2014) recently described H. maculicaudus from New Zealand; this species appears to fall into the H. striatissimus group. Hymenocephalus maculicaudus is unique within the genus in having a distinctive mid-lateral line of black melanophores on the anterior portion of the tail (vs. absent in all other congeners). It further differs from H. striatissimus in its lower counts of gill rakers [16–20 (modally 18) vs. 20–24 (22) on the inner side of the first arch; 15–20 (17) vs. 19–23 (21) on the outer side of the second arch].

In Japanese waters, H. striatissimus is most similar to H. hachijoensi s Okamura, 1970 and H. yamasakiorum Nakayama, Endo & Schwarzhans, 2015 in general appearance, but differs notably from the latter two species in having a shorter barbel (14–23% PRL vs. 36–52% in H. hachijoensis , 73% in H. yamasakiorum ) and an otolith with a single colliculum (vs. ostial and caudal colliculi not fused).

Figures

FIGURE 143. Fresh specimens of Hymenocephalus striatissimus. (A) BSKU 92222, 157 mm TL, Mimase fish market, Kochi Pref., Pacific; (B–D) BSKU 113966, 20.0 mm HL, 159+ mm TL, Tosa Bay off Susaki, Kochi Pref., Pacific. (A–B) Lateral views; (C) dorsal and (D) ventral views of the head and trunk. [Photos: N. Nakayama]

FIGURE 144. Possible holotype of Hymenocephalus striatissimus. USNM 50934 (1 or 2 spec.), 16.7 mm HL, 99+ mm TL, Suruga Bay, Shizuoka Pref., Pacific., 306 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]

FIGURE 145. Scanning electron micrographs showing a body scale (from the dorsum below the interdorsal space) of Hymenocephalus striatissimus. BSKU 43410, 31.3 mm HL. (A) View from above; (B) oblique view. [Photos: NSMT]