Notoscopelus japonicus ( Tanaka, 1908 )

Su, Yo, Huang, Jian-Fu & Yang, Fan-Yi, 2025, A southward range extension of the Japanese lanternfish, Notoscopelus japonicus (Actinopterygii, Myctophiformes, Myctophidae), from Taiwan, northwestern Pacific Ocean, with a checklist of myctophids from Taiwan, Acta Ichthyologica et Piscatoria 55, pp. 123-131 : 123-131

Notoscopelus japonicus ( Tanaka, 1908)

English name: Japanese lanternfish New Chinese name: 日本背燈魚 Fig. 1 ; Tables 1 , 2 .

Macrostoma quercinum japonicum Tanaka, 1908. — Tanaka (1908): 5 (Type locality: off Misaki, Sagami Bay, Japan; holotype: FMNH 80459)

Notoscopelus japonicus ( Tanaka, 1908). — Bekker (1967): 147 (Ogasawara Islands, Japan). — Nafpaktitis 1975: 76 (mentioned). Fujii and Uyeno 1976: 229 (redescription). — Paxton 1979: 16 (listed). — Fujii (1984): 75 (description). — Peden et al. (1985): 7 (northeastern Pacific Ocean). Peden and Hughes (1986): 3 (west coast of Canada). — McAllister (1990): 110 (listed, Canada). — Shinohara et al. (1996): 167 (northern Honshu, Japan). — Sheiko and Fedorov (2000): 22 (Kamchatka Peninsula). — Shinohara et al. (2001): 301 (listed, Tosa Bay, Japan). — Nakabo in Nakabo (2002): 385 (in key, Japan). — Shinohara et al. (2005): 412 (listed, Ryukyu Islands, Japan). — Mundy (2005): 232 (listed, Hancock Seamounts, Hawaii). — Balanov et al. (2009): 671 (northern Japan). — Nakabo and Kai (2013): 455 (in key, Japan). — Shinohara et al. (2014): 239 (listed, Japan). — Parin et al. (2014): 159 (listed, Russia). — Park et al. (2019): 425 (larval record, Korea). — Balushkin and Prirodina (2020): 43 (listed, Russia). — Nakagawa and Motomura (2020): 590 (new record from northern Ryukyu Islands, Japan). — Love et al. (2021): 71 (listed, Alaska).

Specimens examined.

NMMB-P 41347, 126.5 mm SL, male, off Dong-gang fishing port (ca 22°22′22″N, 120°27′34″E), Pingtung, southwestern Taiwan, 23 November 2024, collected by K.-S. Wu . TOU-AE 10942, 122.1 mm SL, male, off Daxi fishing port (ca 24°56′28.16″N, 121°52′12.21″E), Yilan, northeastern Taiwan, commercial trawler, 28 February, collected by J.-F. Huang . TOU-AE 10943, 130.9 mm SL, sex undetermined, and TOU-AE 10944, 134.2 mm SL, male, off Daxi fishing port , Yilan, northeastern Taiwan, commercial trawler, 27 March 2023, collected by J.-F. Huang .

Description of Taiwanese specimens.

Meristic and morphometric data are provided in Tables 1 , 2 .

Dorsal-fin rays 20–21; pectoral-fin rays 11 (left) / 11–3 (right); pelvic-fin rays 9 / 9; anal-fin rays 18–20; principal caudal-fin rays 10 + 9, uppermost and lowermost rays unbranched; procurrent caudal-fin rays 10–11 and 11 on upper and lower lobes, respectively; gill rakers on outer face of first gill arch 8 + 1 + 16 = 25 (total); lateral-line scales 42–44 / 42 – 43; vertebrae 16–17 + 24–26 = 41–42.

Body slender, depth at dorsal-fin origin 6.0– 6.6 in SL; body slightly compressed and oval in trunk section, width 3.1–4.0 in HL. Head small, length 3.9–4.2 in SL; upper profile of head gently curved, nearly straight to dorsal-fin origin; eyes small, width 4.1–4.7 in HL; snout rounded and short, not extending before premaxilla, length 6.3–7.0 in HL; interorbital space convex, width 3.6–3.9 in HL; postorbital length 1.5 in HL.

Mouth large, upper-jaw length 1.4 in HL; posterior end of maxilla nearly reaching posterior margin of preopercle. Two nostrils situated at middle of snout, both slightly above horizontal through center of eye; posterior nostril slightly larger than anterior nostril. Symphysis of premaxillae notched and naked. Symphysis of dentaries without knob and naked. Supramaxilla single, small and rounded; situated above posterior portion of maxilla. Premaxilla and dentary covered with villiform teeth on lateral and medial surfaces. Palatine with narrow band of teeth; vomer naked; endopterygoid with villiform teeth. Body scales deciduous, scales on body ctenoid (based on remaining scales). Isthmus with scales.

Gill rakers rod-shaped and laterally compressed; its lateral and mesial surfaces covered with small conical teeth; rakers on outer row of first arch longer than rest. Short rakers, some forming bumps present on inner face of outer three arches. Fifth ceratobranchial with small conical teeth. Second pharyngeal arch with elongated villiform tooth patch. Third pharyngeal arch with elongated tear-drop shaped conical tooth patch. Fourth pharyngeal arch with rounded conical tooth patch.

Dorsal-fin base 3.7–3.8 in SL; its origin anterior to pelvic-fin origin and its end posterior to anal-fin origin; last two rays elongated. Pectoral fin elongated, its length 2.4–2.6 in HL, nearly reaching pelvic-fin origin when adpressed. Pelvic fin situated posteriorly, at midline of pectoral- and anal-fin origins. Anal-fin base 4.7–5.2 in SL. Adipose fin small, its origin above end of anal-fin base; last two rays elongated. Caudal fin forked, length 1.2 in HL. Caudal peduncle rather long, its height 2.9–3.3 in HL; its length 0.9–1.0 in HL.

Photophores (Fig. 1 ).

AOa 8–10, with last one slightly raised; AOp 6–7; Op 2; PLO 1; PO 5, arranged in 1 + 3 + 1, with last one raised and in front of pelvic-fin origin; Pol 2, with first one before end of anal-fin base and posterior one after end of anal-fin base; Prc 4, arranged in 2 + 2; PVO 2, with second one above pectoral-fin base; SAO 3, all anterior to anal-fin origin; VO 4–5. Dn well developed, forming crescent shape and situated at 10 o’clock of eye; Vn present but small, situated at 8 o’clock of eye. No trace of Ant, Cp, So, and Suo. INGL and SUGL present in males but obscure, without distinct borderline.

Coloration.

When fresh (Fig. 1 ), body pale, with scale pockets outlined by black border. Head uniformly black. All fin rays dusky, with caudal fin darker at its base.

When preserved, coloration similar to that of fresh. Inner surface of operculum, gill arch and rakers, and oral cavity dusky.

Distribution.

Previously known from temperate waters in the northern Pacific Ocean, including Russia ( Sheiko and Fedorov 2000; Parin et al. 2014; Balushkin and Prirodina 2020), Korea ( Park et al. 2019), Japan ( Bekker 1967; Fujii and Uyeno 1976; Fujii 1984; Shinohara et al. 1996, 2001, 2005, 2014; Balanov et al. 2009; Nakagawa and Motomura 2020), Hancock Seamount, Hawaii ( Mundy 2005), Canada ( Peden and Hughes 1986; McAllister 1990), and Alaska ( Love et al. 2021). A mesopelagic species that inhabits below 300 m during the daytime and migrated to 20–200 m depth at night ( Watanabe et al. 1999). Our specimens represent the southernmost record of this species.

Figures

Figure 1. Fresh specimens of Notoscopelus japonicus. (A) NMMB-P 41347, 126.5 mm SL, photo by Y. - C. Hsu. (B) TOU-AE 10942, 122.1 mm SL, left – right reversed. (C) TOU-AE 10943, 130.9 mm SL. (D) TOU-AE 10944, 134.2 mm SL.