Nezumia spinosa ( Gilbert & Hubbs, 1916 )

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 262-264

Nezumia spinosa ( Gilbert & Hubbs, 1916)

[Japanese name: Goten-hige]

( Figs. 175B , 176–177 ; Appendix 3-10F)

Lionurus spinosus Gilbert & Hubbs, 1916:199 , pl. 10, fig. 2 [original description; holotype: USNM 76868, from “Eastern Sea” (East China Sea), Albatross sta. 4915, in 427 ftm (781 m)]; Okada & Matsubara 1938:453 (in key; Japan); Matsubara 1955:1317 (in key; Japan); Matsubara 1965:510 (compiled; Japan; new Japanese name: “Goten-hige”).

Lionurus proximus (not Smith & Radcliffe in Radcliffe 1912): Gilbert & Hubbs 1916:201 [in part, 1 spec. ( CAS-SU 22941 ) from East China Sea, Albatross sta. 4918] .

Nezumia spinosa: Okamura 1984b:94 , pl. 345, fig. A (compiled); Okamura 1988:94, pl. 345, fig. A (compiled); Nakabo 1993:360 (in key; Japan); Nakabo 2000:424 (in key; Japan); Nakabo 2002:424 (in key; Japan); Suetsugu & Ohta 2005: table 3 (questionable; listed; Enshu-nada); Shao et al. 2008b: table 2 (3 spec. listed from southwestern Taiwan and South China Sea; first Taiwanese record); Nakabo & Kai 2013:500 (in key; Japan); Iwamoto et al. 2015:94, fig. 20 (brief description; 6 spec. from southwestern Taiwan and South China Sea); Motomura 2020:39 (listed; Japan).

Diagnosis. A species of Nezumia with 8 pelvic-fin rays. Snout moderately long, conical, protruding well beyond upper jaw, length 27–33% HL, ventral contour oblique in lateral view; underside of head almost completely naked. Second spinous ray of first dorsal fin extremely prolonged (height of fin 120–138% HL). Body scales covered with short, greatly reclined, needle-like spinules densely scattered over exposed portion; posteriormost spinules extending well beyond scale margin; no spinules especially enlarged; scales below second dorsal-fin origin 7.5–8.5. Cephalic sensory pores well developed especially on mandibular and infraorbital canals. No prominent dark band encircling trunk; first dorsal fin uniformly dark.

Material examined. 9 specimens. Holotype of Lionurus spinosus: USNM 76868 (46.4 mm HL, 262+ mm TL), southwest of Kamikoshiki-jima Island, Kagoshima Pref., Japan, East China Sea , 31.5167ºN, 129.4250ºE, 427 ftm (781 m), Albatross sta. 4915, 9-ft Agassiz beam trawl, 12 Aug. 1906. Non-types : Japan: CAS-SU 22941 (1, 19.6 mm HL, 117+ mm TL), west of Yaku-shima Island , Okinawa Trough , 30.3667ºN, 129.1417ºE, 660 m, Albatross sta. 4918, 13 Aug. 1906 ; SFU 1840 (1, 37.0 mm HL, 176+ mm TL), South China Sea , Apr. 1982. Australia: CSIRO H1971-01 (1, 40.8 mm HL, 199+ mm TL), off Queensland, 16.9167ºS, 151.5667ºE, 880 m, 6 Dec. 1985 ; CSIRO H1961-01 (1, 40.4 mm HL, 197+ mm TL), off Queensland, 18.9000ºS, 150.4833ºE, 1005–1013 m, 25 Nov. 1985 ; CSIRO H2549- 10 (1, 48.8 mm HL, 254+ mm TL), off Western Australia, 21.8500ºS, 113.7667ºE, 650–685 m, 24 Jan. 1991 ; CSIRO H2580-04 (1, 47.5 mm HL, 249+ mm TL), off Western Australia, 27.1000ºS, 112.3667ºE, 713–714 m, 31 Jan. 1991. Timor Sea: BSKU 16687 (1, 35.5 mm HL, 183+ mm TL), BSKU 16688 (1, 19.4 mm HL, 130 mm TL), 9.4500ºS, 127.9767ºE, 690–850 m, R/ V Hakuho-maru, cr. KH-72-01, coll. O. Okamura, 18–9 Jan. 1972.

Counts and measurements. Based on 9 specimens (19.4–48.8 mm HL, 117+–262+ mm TL). Counts: first dorsal-fin rays II,8–10; pectoral-fin rays i18–i22; pelvicfin rays 8; gill rakers on first arch (outer/inner) 4–11/9– 11, on second arch 8–11/9–11; longitudinal scales 37–40; transverse scale rows below first dorsal-fin origin 7.5– 12, below first dorsal-fin midbase 5.5–9, below second dorsal-fin origin 7.5–8.5, above anal-fin origin 22–23.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 27–33 (36–46); orbit diameter 27–32 (38–43); postorbital length 41–47 (57–63); postrostral length 71– 75; orbit–preopercle distance 33–40 (46–53); suborbital width 11–19 (15–26); upper-jaw length 27–33 (35–45); length of rictus 20–26 (27–34); length of premaxillary tooth band 14–21 (20–28); preoral length 18–28 (24–39); distance between tip and lateral angle of snout 11–20 (15– 26); snout width 20–27 (27–36); internasal width 16–20 (21–28); interorbital width 19–22 (25–31); body width over pectoral-fin bases 41–58 (55–82); body depth at first dorsal-fin origin 72–82 (102–115); body depth at anal-fin origin 63–77 (88–103); prepelvic length 104–124 (138– 170); preanus length 118–137 (156–188); preanal length 141–156 (194–216); isthmus–pelvic distance 33–40 (45– 54); isthmus–anus distance 45–49 (63–65); isthmus–anal distance 60–78 (84–106); pelvic–anal distance 32–43 (44–60); anus–anal distance 16–29 (22–40); pelvic-fin length 55–88 (78–124); pectoral-fin length 51–121 (71– 162); predorsal length 110–124 (154–168); height of first dorsal fin 120–138 (165–195); length of first dorsal-fin base 23–30 (32–42); interdorsal length 34–56 (46–75); length of gill slit 10–14 (13–19); length of posterior nostril 6–11 (8–15); barbel length 9–14 (12–20).

Size. To at least 26 cm TL ( Iwamoto & Williams 1999). The holotype is the largest specimen of this species, measuring 262+ mm TL.

Distribution. Widely distributed in the Indo-West Pacific from South Africa, eastward to Australia and New Caledonia, and northward to Japan, at depths of 420–1258 m ( Gilbert & Hubbs 1920; Iwamoto & Anderson 1994; Iwamoto & Merrett 1997; Iwamoto & Williams 1999; Shao et al. 2008a, 2008b; Last et al. 2014; Iwamoto et al. 2015; Nakayama & Endo 2015). Very rare in Japanese waters, but not in other parts of its range. The Japanese records based on only two Albatross specimens collected from the Okinawa Trough in 660‾ 781 m (Appendix 3-10F).

Remarks. For a full description see the original description given by Gilbert & Hubbs (1916). Nezumia spinosa was originally described from a single specimen collected from the East China Sea off Japan ( Fig. 176 ). Subsequently, it has been widely recorded from the Indo-West Pacific, including the South China Sea off Taiwan ( Shao et al. 2008a, 2008b; Iwamoto et al. 2015), the Philippines ( Gilbert & Hubbs 1920), Western Australia ( Iwamoto & Williams 1999), New Caledonia and Fiji ( Iwamoto & Merrett 1997; Merrett & Iwamoto 2000), Timor Sea (Nakayama & Endo 2015), and eastern Indian Ocean off South Africa ( Iwamoto & Anderson 1994). However, N. spinosa appears to include multiple species, as previous authors have mentioned (see below). Gilbert & Hubbs (1920:554) indicated that four small specimens from the Philippines differ from the holotype in having a larger head and a deeper body, suggesting the presence of a second species. Similarly, Iwamoto & Williams (1999:204, table 6) highlighted notable differences in meristic and morphometric characters between African and Australian populations of N. spinosa , particularly in the mode of first dorsal-fin ray counts (II,8 vs. II, 9 in the African and Australian populations respectively), preoral length (28–35% HL vs. 18–29%), and postorbital length (37–42% vs. 43–46%). They implied that the African population might represent an undescribed species, noting “isolation has resulted in significant divergence between the populations on each side of the Indian Ocean”.

The Japanese records of N. spinosa are based on only two specimens: one is the holotype and the other is a small specimen (CAS-SU 22941, 19.6 mm HL, 117+ mm TL; Fig. 177 ) collected from the type locality. This second specimen was initially reported by Gilbert & Hubbs (1916) as N. proxima (Smith & Radcliffe in Radcliffe, 1912), but it was subsequently re-identified as N. spinosa by Iwamoto & Merrett (1997).Although Okamura (1970a) considered N. spinosa as a junior synonym N. proxima , he ( Okamura 1984a, 1984b) resurrected this species after an examination of its holotype. In his list of fishes from Iwate Pref., Maruyama (1971) listed N. spinosa with a question mark (as Lionurus spinosus ). Although the whereabouts of his specimen(s) is unknown, it probably represents N. proxima , considering the common occurrence of this species along the Pacific coasts of northern Japan.

Relationships and comparisons. Nezumia spinosa belongs to the N. spinosa group as defined by Nakayama & Endo (2015) (see the Remarks, relationships, and comparisons of N. shinoharai ), and is most similar to N. infranudis Gilbert & Hubbs, 1916 . The latter species is so far represented by the holotype from the Celebes Sea and an additional specimen recently reported from the Timor Sea (Nakayama & Endo 2015). Nezumia spinosa is readily distinguished from that species by having lower counts of pelvic-fin rays (8 vs. 11).

Figures

FIGURE 175. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of two species of the Nezumia spinosa group. (A) N. shinoharai, NSMT-P 97667, holotype, 38.0 mm HL; (B) N. spinosa, USNM 76868, holotype, 46.4 mm HL. Views from above. [Photos: reproduced from Nakayama & Endo (2012: fig. 4A, E)]

FIGURE 176. Holotype of Lionurus spinosus (= Nezumia spinosa). USNM 76868, 46.4 mm HL, 262+ mm TL, southwest of Kamikoshiki-jima Island, Kagoshima Pref., East China Sea, 781 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of head. Preserved condition. [Photos: N. Nakayama]

FIGURE 177. Preserved juvenile specimen of Nezumia spinosa. CAS-SU 22941, 19.6 mm HL, 117+ mm TL, west of Yaku-shima Island, Kagoshima Pref. East China Sea, 660 m depth. Lateral view. [Photo: N. Nakayama]