Lestrolepis japonica ( Tanaka, 1908 )

Ho, Hsuan-Ching, Tsai, Song-Yu & Li, Hsing-Hui, 2019, The barracudina genera Lestidium and Lestrolepis of Taiwan, with descriptions of two new species (Aulopiformes: Paralepididae), Zootaxa 4702 (1), pp. 114-139 : 127-130

Lestrolepis japonica ( Tanaka, 1908)

Japanese barracudina

Figures 3C , 4 A–E; Table 1–8

Lestidium Japonicum Tanaka, 1908:27 (type locality: Sagami Sea, Japan).

Lestrolepis Japonica : Chen & Yu, 1986:324.

Materials examined. Collected from off Dong-gang, southwestern Taiwan, except for as indicated: NMMB-P3684 (3, 187–194), 28 May 2002 . NMMB-P7923 (1, 202), 11 Jun. 2004 . NMMB-P7028 (1, 193), 20 Feb. 2004 . NMMB- P7089 (4, 170–196), Shiao-liu-qiou, Pingtung, 26 Dec. 2003 . NMMB-P8026 (1, 190), Fang-shan , Pingtung, 17 Jun. 2004 . NMMB-P11219 (4, 192–202), 5 Jul. 2007 . NMMB-P11222 (9, 185–203), 30 Oct. 2010 . NMMB-P11273 (4, 184–198), 15 Dec. 2009 . NMMB-P12016 (4, 193–203), 18 Dec. 2011 . NMMB-P12170 (2, 183–185), 31 Dec. 2010 . NMMB-P13734 (1, 202), 2 Jul. 2011 . NMMB-P16389 (4, 174–193), 23 Feb. 2012 . NMMB-P20331 (1, 202), 25 May 2013 . NMMB-P21167 (2, 200–203), 2 Apr. 2014 . NMMB-P21888 (1, 205), 12 Dec. 2013 . NMMB- P21992 (3, 164–200), 31 Dec. 2013 . NMMB-P22080 (8, 185–222, stained), 5 Jan. 2015 . NMMB-P22468 (1, 206), 30 Oct. 2015 . NMMB-P22469 (6, 183–211, stained), 30 Jan. 2015 . NMMB-P22847 (2, 88–110), 10 Mar. 2015 . NMMB-P23817 (1, 178), 4 Feb. 2016 . NMMB-P23818 (1, 193), 4 Feb. 2016 . NMMB-P24620 (1, 170), 27 Jun. 2016 . NMMB-P24623 (2, 129–150), 21 Sep. 2015 . NMMB-P24629 (1, 168), 27 Jun. 2016 . NMMB-P25538 (21, 139–187, stained), 4 Feb. 2016 . NMMB-P25539 (1, 186), 8 Jan. 2017 . NMMB-P25542 (2, 186–190, stained), 20 Jan. 2017 . NMMB-P25543 (12, 168–191), 20 Jan. 2017 . NMMB-P25544 (5, 123–140), 20 Jan. 2017 . NMMB- P30788 (4, 85–130, stained), out of NMMB-P25545 . NMMB-P25578 (30, 50–100), 20 Jan. 2017 . NMMB-P27933 (17, 144–195), 6 Dec. 2017 . NMMB-P27934 (16, 150–206), 6 Dec. 2017 . NMMB-P27936 (20, 168–203), 6 Dec. 2017 . NMMB-P30788 (4, 78–130, stained), out of NMMB-P25545 . NMMB-P30799 (24, 103–210), 27 Mar. 2018 . NMMB-P30800 (29, 158–224), 16 Jul. 2017 .

Diagnosis. A moderately elongate species in Lestrolepis with body depth 13–16 times in SL; DFO clearly before midline of V–A, V–D 32.5–43.1% V–A; anal-fin rays 36–40; vertebrae: prehaemal 30–32, prepelvic 30–33, predorsal 36–40, preanal 48–51, caudal 52–58; and total 82–88; total lateral-line scales 66–72; and narrow band of black chromatophores along lower portion of abdominal ridge.

Description. Dorsal-fin rays 9; pectoral-fin rays 12–13 (mainly 13); pelvic-fin rays 9; anal-fin rays 36–40 (39); lateral line incomplete, running to above middle of anal-fin base; 31–32 scales before VFO, 38–40 before DFO, 49– 50 before AFO, and 65–72 in total, 60–65 large scales along most of the canal, followed by 2–9 small scales in the rear portion. Vertebrae: prehaemal 30–32; caudal 52–58; prepelvic 30–33; predorsal 36–40; preanal 48–51; and total 82–88. Gill rakers: 9–15 on upper limb (epibranchial) and 24–31 on lower limb (13–19 on ceratobranchial+10–14 on hypobranchial).

Body elongate and slender, strongly compressed, depth at pectoral-fin depth 13–16 in SL. Caudal peduncle shorter than eye diameter; its depth 1.8–2.4% SL. Abdominal ridge with low adipose fin between pectoral and pelvic fins; ventral adipose fin well developed along margin between anus and anal fin.

Head moderately long and pointed, slightly triangular; its length 4.7–5.0 in SL. Mouth terminate, moderately large, its gape extends to middle of eye; lower jaw slightly upturned at tip. Eye large, its diameter 5.7–6.4 in HL. A light organ in front of eye ( Fig. 4D ); a short luminescent duct along lower margin of orbit (inner side of first and second infraorbitals). Seven infraorbital bones, the first slender, the fifth and sixth well-expanded posteriorly, the seventh small. Interorbital space narrow, its width 5.6–8.3 in HL. Four gill arches, all with gill filaments. The third and fourth arches mostly connected by membranes. Pseudobranchs present, inside a deep pocket.

DFO well behind pelvic fins and middle of body, predorsal length 1.6–1.7 SL, but clear before midline of VFO and AFO. Pectoral fin at same level as posterior margin of gill cover, its upper base about same level of lower margin of eye. Pelvic fin at or slightly behind middle of body, prepelvic fin length 1.8–1.9 in SL. Anal fin originating posterior fourth of body, preanal fin length 1.3–1.4 in SL. Adipose fin above rear portion of anal-fin base.

Two or three small fangs at tip of upper jaw, followed by single row of small retrose teeth along upper jaw, gradually smaller on posterior portion. Vomerine teeth absent. Two rows of fangs on lower jaw, gradually smaller posteriorly, those in outer row short and fixed; those in inner row long, each with a knife-like tip, and depressible. Two rows of fangs on each palatine, those on outer row smaller than those on inner row. Teeth on tongue small and scattered, one row on each side. Gill rakers present on epibranchial, ceratobanchial and hypobanchial; shield shape, each with 1–3 small teeth. Teeth on pharyngeal arch slender, forming an ovoid patch with about five rows at middle.

Body devoid of scales, except for a single row of lateral-line scales originating from above pectoral-fin girdle and running to above about middle of anal-fin base. Lateral-line scales as high as it’s wide, gradually smaller and becoming narrower posteriorly; 5–8 (mainly 6–7) pores forming an irregular cluster on each side of lateral-line scales before dorsal fin.

Luminescent duct well developed at ventral abdomen cavity, originating from below pectoral fin ( Fig. 4B ) and divided into two branches from its origin to anus.

Coloration. Body semitransparent when fresh, creamy white in preservation. Chromatophores present on the surface of first to the third infraorbital bones, upper margin of eye, anterior three-fourths of upper jaw, and along upper margin of lower jaw. Upper fourth of body covered by tiny and dense chromatophores, extending to upper margin of lateral line ventrally. Bases of dorsal, pectoral, and anal-fin rays with black pigments. Single row of large chromatophores forming a narrow black margin or slightly above the ridge with a narrow pale margin ( Fig. 4E ); ventral adipose fin densely covered by small chromatophores. Luminescent duct silver white with black pigments on its upper surface (e.g. can be seen through the semitransparent muscle). Chromatophores present on inner gill chamber and branchiostegal rays; branchiostegal membranes colorless; gill arches blackish; and mouth cavity white.

Size. Appear to be a small species with adults reaching 222 mm TL.

Distribution. Widespread in the western Pacific Ocean. It is very common in the bycatch of midwater and bottom trawl, and it is the most abundant species among the paralepidids in Taiwan; confirmed records from Japan, Taiwan, the Philippines, northwestern Australia, and South China Sea.

Remarks. The first author examined specimens collected from off Australia and found the specimens have a slightly longer and more pointed snout. However, the vertebral formula and body proportions are nearly identical and thus the population from Australia is recognized as same with those from the northwestern Pacific population. This is the most common and abundant paralepidid found in Taiwan, and it is usually collected by midwater trawl as bycatch of Sakura shrimp ( Lucensosergia lucens ) and sometimes by bottom trawl. Most individuals feed on small fishes rather than shrimps.

Figures

FIGURE 3. Demostration of orgin of dorsal fin and mid-point of origins of pelvic and anal fins (bar). A. Lestrolepis nigroventralis sp. nov. B. L. intermedia. C. L. Japonica.

FIGURE 4. Lestrolepis Japonica, NMMB-P25542. A–C. 190 mm SL.A. lateral view. B. ventral view of head, arrow points the origin of luminous organ. C. trunk, arrows point to origins of dorsal fin (above), pelvic fin (left) and anal fin (right); stained. D–E. 186 mm SL. D. lateral view of head. E. lateral view of trunk. Anterior to left.