Pseudonezumia cetonuropsis ( Gilbert & Hubbs, 1916 )

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 272-274

Pseudonezumia cetonuropsis ( Gilbert & Hubbs, 1916)

[Japanese name: Chidori-hige]

( Figs. 185–186 , 187 A–B; Appendix 3-11D)

Lionurus cetonuropsis Gilbert & Hubbs, 1916:202 , pl. 11, fig. 1 [original description; holotype: USNM 76869, from “off east coast of Hondo” (off Cape Omaezaki), Albatross sta. 5084, in 918 ftm (1690 m)]; Okada & Matsubara 1938:453 (in key; Japan); Matsubara 1955:1316 (in key; Japan); Matsubara 1965:509 (compiled; Japan; new Japanese name: “Chidorihige”).

Nezumia cetonuropsis: Okamura 1970a:103 [new combination; description after Gilbert & Hubbs (1916)]; Okamura 1970b: table 1 (listed; Japan).

Paracetonurus cetonuropsis: Tominaga & Uyeno 1981:489 (listed; Japan).

Pseudonezumia cetonuropsis: Okamura 1984b:95 , pl. 345, fig. D (compiled); Okamura 1988:95, pl. 345, fig. D (compiled); Nakabo 1993:356 (in key; Japan); Okamura 1997:128, fig. 18 (compiled); Nakabo 2000:420 (in key; Japan); Shinohara et al. 2001:306 (listed; Tosa Bay); Nakabo 2002:420 (in key; Japan); Nakabo & Kai 2013:496 (in key; Japan); Iwatsuki et al. 2017:32 (listed; Hyuga-nada); Motomura 2020:39 (listed; Japan).

Diagnosis. Underside of snout broadly naked above upper lip; spinules on body scales supported by narrowly developed buttresses; transverse scale rows below first dorsal-fin origin 9–11, below first dorsal-fin midbase 7–9; orbit diameter 22–25% HL; preoral length 26–29% HL; postorbital length 42–45% HL; orbit–preopercle distance 35–41% HL; interorbital width 31–37% HL; barbel length 5–11% HL; caudal depth at base of 40th anal-fin ray 24– 29% HL; body uniformly dusky to paler brown, except for darker abdomen and black periproct.

Material examined. 16 specimens. Holotype of Lionurus cetonuropsis: USNM 76869 (43.8 mm HL), off Cape Omaezaki , Shizuoka Pref., Enshu-nada , Japan , 34.0000ºN, 137.8278ºE, 918 ftm (1679 m), Albatross sta. 5084, 9-ft Agassiz beam trawl, 20 Oct. 1906. Non-types : Japan: BSKU 43443 (1, 39.4 mm HL, 213+ mm TL), southeast of Okino-shima Island , 32.5233ºN, 132.4650ºE, 1642–1651 m, R/ V Tansei-maru, cr. KT-86-19, sta. D-1, tr. 1, 3-m beam trawl, 16 Dec. 1999 ; BSKU 86837 (1, 30.6 mm HL, 207+ mm TL), south-southwest of Okinoshima Island , 32.3038ºN, 132.3592ºE, 1678–1690 m, R/ V Tansei-maru, cr. KT-99-18, sta. BT-5, beam trawl, coll. H. Endo and S. Nagatomo, 16 Dec. 1999 ; BSKU 57408 (1, 50.8 mm HL, 316 mm TL), Bungo Channel, no further information ; BSKU 86863 (1, 46.0 mm HL, 321+ mm TL), Kumano-nada, 33.7500ºN, 136.5955ºE, 2035–2043 m, R/ V Tansei-maru, cr. KT-99-18, sta. BT-8, beam trawl, coll. H. Endo and S. Nagatomo, 20 Dec. 1999 ; BSKU 18802 (1, 44.8 mm HL, 293 mm TL), BSKU 18803 (1, 38.4 mm HL, 221+ mm TL), southeast of Owase , Kumano-nada, 33.8117ºN, 136.5800ºE, 2050 m, FRV Soyo-maru, sta. 18, beam trawl, 27 Jun. 1955 ; * BSKU 47908 (1, 54.9 mm HL, 345+ mm TL), Kumanonada, 33.7085ºN, 136.6092ºE, 2034–2036 m, R/ V Tanseimaru, cr. KT-09-13, sta. T1, 31 Aug. 1990 ; BSKU 86851 (1, 42.6 mm HL, 296 mm TL), Kumano-nada, 33.7332ºN, 136.5788ºE, 2035–2051 m, R/ V Tansei-maru, cr. KT-99- 18, sta. BT-7, beam trawl, coll. H. Endo and S. Nagatomo, 20 Dec. 1999 ; BSKU 86866 (1, 42.3 mm HL, 226+ mm TL), Kumano-nada, 33.8333ºN, 136.5433ºE, 1947–2023 m, R/ V Tansei-maru, cr. KT-99-18, sta. BT-9, beam trawl, coll. H. Endo and S. Nagatomo, 20 Dec. 1999 ; BSKU 86847 (1, 40.6 mm HL, 292 mm TL), Kumano-nada, 33.6362ºN, 136.5063ºE, 2072–2074 m, R/ V Tansei-maru, cr. KT-99-18, sta. BT-6, beam trawl, coll. H. Endo and S. Nagatomo, 20 Dec. 1999 ; *NSMT-P 78831 (2, 47.0– 48.8 mm HL, 314–346 mm TL), Kumano-nada, 33.7650ºN, 136.6967ºE, 2019–2054 m, R/ V Tansei-maru, cr. KT-86-06, sta. KN6, trawl, 28 May 1986 ; NSMT-P 19019 (1, 45.4 mm HL, 230+ mm TL), east of Hachijo Island, Shichito-Iojima Ridge, 33.1550ºN, 140.7933ºE, 1700 m, 25 Jul. 1975 ; NSMT-P 101338 (2, 49.0– 50.3 mm HL, 298+–321+ mm TL), southeast of Okinawa-jima Island, Ryukyu Trench, 26.2840ºN, 128.4505ºE, 1943–2013 m, R/ V Hakuho-maru, cr. KH-05-01, sta. PS-07, 4-m ORE beam trawl, 24 May 2005.

Counts and measurements. Based on 13 specimens (30.6–50.8 mm HL, 207+–321+ mm TL). Counts: first dorsal-fin rays II,8–10; pectoral-fin rays i15–i20; pelvicfin rays 6; gill rakers on first arch (outer/inner) 8–11/10– 11, on second arch 10/11; longitudinal scales 51–63; transverse scale rows below first dorsal-fin origin 9–11, below first dorsal-fin midbase 7–9, below second dorsalfin origin 9–11.5.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 34–39 (50–60); orbit diameter 22–25 (34–39); postorbital length 42–45 (64–67); postrostral length 65–68; orbit–preopercle distance 35–41 (52–60); suborbital width 15–18 (23–28); upper-jaw length 27–31 (41–46); length of rictus 23–24 (33–36); length of premaxillary tooth band 13–17 (20– 25); preoral length 26–29 (39–45); distance between tip and lateral angle of snout 21–22 (31–34); snout width 34– 38 (50–56); internasal width 29–32 (42–48); interorbital width 31–37 (46–55); body width over pectoral-fin bases 38–54 (58–80); body depth at first dorsal-fin origin 67–80 (100–119); body depth at anal-fin origin 60–72 (89–106); caudal depth at base of 40th anal-fin ray 24–29 (35–42); prepelvic length 100–117 (150–174); preanus length 123–140 (183–208); preanal length 127–147 (190–218); isthmus–pelvic distance 23–27 (34–41); isthmus–anus distance 46–57 (69–84); isthmus–anal distance 53–62 (79–93); pelvic–anal distance 29–42 (44–62); anus–anal distance 5–11 (7–17); pelvic-fin length 28–47 (41–70); pectoral-fin length 47–56 (72–85); predorsal length 105– 115 (156–170); height of first dorsal fin 65–78 (96–116); length of first dorsal-fin base 19–23 (28–34); interdorsal length 32–42 (48–63); length of gill slit 12–15 (18–23); length of posterior nostril 5–10 (8–15); barbel length 5–11 (8–16).

Size. To about 32 cm TL (BSKU 86863, 321+ mm TL, Kumano-nada, Japan).

Distribution. So far known from only Japanese waters (Appendix 3-11D). Depth range 1642‾ 2074 m.

Remarks. For further morphological details see the original description of the species given by Gilbert & Hubbs (1916). Pseudonezumia cetonuropsis was initially described as a new species of Lionurus G̹nther, 1887 based on two specimens collected from off Cape Omaezaki, Enshu-nada, Japan ( Fig. 186 ). Gilbert & Hubbs (1916) also reported one damaged juvenile collected with the holotype; this second specimen was not found during the author’s visits to the Smithsonian Institution in 2011 and 2017.

Maruyama (1971) listed P. cetonuropsis from Iwate Pref., northern Honshu (as Lionurus cetonuropsis ), but with a question mark. Because his list was primarily based on specimens collected from local fish markets, this record appears to represent a different species of grenadiers. The bathymetric distribution of P. cetonuropsis is confined to bathyal depths below 1600 m, where commercial fisheries have not been conducted.

Shao et al. (2008a, 2008b) recorded P. cetonuropsis from Taiwan based on three specimens collected from the northern South China Sea (ASIZP 66945, 20.5–32.9 mm HL, 135+–161+ mm TL). These specimens were reidentified as P. pusilla ( Sazonov & Shcherbachev, 1982) by Iwamoto et al. (2015).

Relationships and comparisons. Pseudonezumia cetonuropsi s is unlikely to be confused with P. flagellicauda ( Koefoed, 1927) owing to its uniformly dark color (vs. lower jaw and naked area on underside of snout prominently black, and tail abruptly blackish posteriorly), shorter postorbital (42–45% HL vs. 47–53%), narrower cheek (orbit–preopercle distance 35–41% HL vs. 40– 48%), and lower counts of transverse scale rows (9–11 vs. 11–15 below first dorsal-fin origin; 7–9 vs. 10.5–13.5 below first dorsal-fin midbase). In addition, this species is readily distinguished from P. parvipes (Smith & Radcliffe in Radcliffe, 1912) and P. pusilla by having a broad naked area on the underside of the snout (vs. naked area absent or represented by only a narrow ventromedial streak above the upper lip). It further differs from P. flagellicauda and P. pusilla in having a shorter chin barbel (5–11% HL vs. 13–18% in P. flagellicauda , 11–23% in P. pusilla ), and from P. pusilla in having a smaller orbit (22–25% HL vs. 28–37%).

Differences between P. cetonuropsis and P. japonica Okamura, 1970 are subtle, and the species are difficult to distinguish from each other. The possible diagnostic character recognized in this study is the preoral length: 26–29% HL in P. cetonuropsis vs. 20–26% in P. japonica . Accordingly, the snout of P. cetonuropsis is usually much higher than that of P. japonica , if specimens are in good condition ( Fig. 185 vs. Fig. 188 ). A slight difference in the caudal depth also suggests a separation between the two species, with P. cetonuropsis having a slenderer tail compared with P. japonica (depth at base of 40th anal-fin ray 24–29% HL vs. 27–34%). However, these differences are very slight, and may be eliminated if more specimens become available for comparison; the taxonomic status of the two taxa requires further investigation.

Figures

FIGURE 185. Fresh specimen of Pseudonezumia cetonuropsis. BSKU 47908, 54.9 mm HL, 345+ mm TL, Kumano-nada, Pacific, 2034–2036 m depth. Lateral view. [Photo: BSKU]

FIGURE 186. Holotype of Lionurus cetonuropsis (= Pseudonezumia cetonuropsis). USNM 76869, 43.8 mm HL, Enshu-nada off Cape Omaezaki, Shizuoka Pref., Pacific, 1679 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of head. Preserved condition. [Photos: N. Nakayama]

FIGURE 187. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of two species of Pseudonezumia. (A–B) P. cetonuropsis, NSMT-P 78831, 48.8 mm HL; (C–D) P. japonica, BSKU 56976, 50.5 mm HL. (A, C) Views from above; (B, D) oblique views. [Photos: N. Nakayama]

FIGURE 188. Fresh specimen of Pseudonezumia japonica. BSKU 56976, 50.5 mm HL, 273+ mm TL, off Kamaishi, Iwate Pref., Pacific, 1949–2005 m depth. Lateral view. [Photo: H. Endo]