Lestrolepis nigroventralis, Ho & Tsai & Li, 2019

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 : 123-126

Lestrolepis nigroventralis sp. nov.

New English name: Black-belly barracudina

Figures 1 A–C, 2A–D, 3A; Tables 1–8

Lestrolepis intermedia (non Poey, 1868): Chen & Yu, 1986:324.

Holotype. NMMB-P28481 (1, 234), off Dong-gang , Pingtung, southwestern Taiwan, South China Sea, midwater trawl, 0–50 m, 30 Jan. 2018 [from bycatch].

Paratypes. Forty-three specimens, 134–244 mm SL. Collected from off Dong-gang , near the type local- ity : KAUM–I. 125204–125206 (3, 180–185), 27 Mar. 2018 . NMMB-P18105 (2, 220–240, stained), 4 Jan. 2013 . NMMB-P24635 (1, 238), 12 Oct. 2011 . NMMB-P24718 (2, 183–249, stained), 11 Oct. 2016 . NMMB-P25563 (1, 180, stained), 4 Feb. 2016 . NMMB-P25564 (1, 184), 20 Jan. 2017 . NMMB-P25565 (1, 230), 10 Jan. 2017 . NMMB- P27930 (1, 244) , NMMB-P27933 (17, 148–197) , NMMB-P27935 (5, 180–235) , NMMB-P27940 (1, 231), NMMB- P27941 (1, 228) , NMMB-P30790 (4, 177–237, stained), Dong-gang , 6 Dec. 2017 . Japan. NSMT-P48916 (1, 167), south of Sagami Bay, Honshu, southern Japan , 4 Nov , 1995. NSMT-P65466 (1, 134), 36°53.76’N, 141°33.7’E, Pacific coast off Ibaraki, Honshu, southern Japan , 459–530 m, ottet trawl, 20 Oct. 2002 . NSMT-P67598 (1, 230), 28°59.87’N, 127°9.35’E, Each China Sea , 350 m, otter trawl, 5 Nov. 2003 .

Non-types. Collected from near the type locality: NMMB-P26455 (1, 185), 20 Jun. 2017 . NMMB-P27929 (3, 180–234), 16 Jul. 2017 . NMMB-P30803 (18, 102–192), 27 Mar. 2018 . Collected from off Japan: NSMT-P13816 (2, 144–153), off Kanbara , Shizuoka City , Honshu, Suruga Bay, southern Japan, 17 Nov. 1968 . NSMT-P48931 (1, 154), off Pacific cost of Tohoku District, Honshu, southern Japan, 5 Nov. 1995 . NSMT-P65464 (1, 181), 37°45.9’N, 142°9.53’E, Pacific coast off Fukushima, Honshu, Japan, 647–676 m, otter trawl, 19 Oct. 2002 . NSMT-P67563 (1, 145), 31°20.65’N, 128°10.88’E, East China Sea, 392 m, otter trawl, 8 Nov. 2003 . NSMT-P91547 (1, 164+), 38°21.5’N, 141°56,4’E, Pacific coast off Miyagi, Honshu, southern Japan, 280 m, trawl, 23 Oct. 2007 . NSMT- P 102802 (1, 169), 36°58.44’N, 141°25.72’E, off Fukushima, Honshu , southern Japan, 251–252 m, otter trawl, 26 Oct. 2006 .

Diagnosis. A species of Lestrolepis with relatively slender body, body depth 15–19 times in SL; DFO at about midline of V–A, V–D 46.8–55.0% of V–A; VFO at or slightly behind midline of the fish, prepelvic length 50.6– 53.2% SL; vertebrae: prehaemal 32–35, prepelvic 33–35, preanal 53–57, caudal 60–66, and total 94–98; lateral-line scales 75–81; and abdomen ridge with broad black margin.

Description. Dorsal-fin rays 9; pectoral-fin rays 12–13; pelvic-fin rays 9; anal-fin rays 41–43. Lateral line incomplete, running to above middle of anal-fin base; 33–36 scales before VFO, 43–46 before DFO, 53–57 before AFO, 75–81 in total, 69–74 large scales followed by 4–11 smaller ones. Vertebrae: prehaemal 32–35; prepelvic 33–35; predorsal 43–46; preanal 53–57; caudal 60–66; and total 94–98. Gill rakers: 8–13 on upper limb (epibran- chial) and 23–30 on lower limb (13–16 on ceratobranchial+9–14 on hypobranchial).

Body elongate and slender, strongly compressed, depth at pectoral fin 15–19 in SL. Caudal peduncle shorter than eye diameter. Abdomen ridge well-developed, with narrow 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 4.8–5.3 in SL. Mouth terminal, moderately large, its gape extends to middle of eye; lower jaw slightly upturned at tip. Eye large, its diameter 5.8–6.8 in HL. A black antorbital light organ in front of eye; a short luminescent duct along lower margin of orbit (inner side of first and second infraorbitals). Snout moderately long, its length 1.8–1.9 in HL. Seven infraorbital bones, the first slen- der, the fifth and sixth not especially expanded, the last small. Interorbital space narrow, its width 9.0– 10.6 in HL. Four gill arches, all with gill filaments. The third and fourth arches mostly connected by membranes. Pseudobranch present, inside a deep pocket.

DFO well behind pelvic fin and middle of body, and at about middle of VFO and AFO, predorsal length 1.6 in SL. Pectoral fin at same level of posterior margin of gill cover, its upper base at about same level of lower margin of eye. VFO at or slightly behind middle of body, prepelvic fin 1.9–2.0 in SL. AFO at posterior third to fourth of body, preanal fin length 1.3–1.4 in SL. Anal-fin base long. Adipose fin above rear portion of anal-fin base. Anus behind pelvic-fin base, at about tip of the appresed pelvic fin.

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 absence. 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 epibranchials, ceratobanchials and hypobanchials; shield shape, each with 1–3 small teeth. Teeth on pharyngeal arch slender, forming an oval patch with about 5 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 about one-sixth of SL before caudal fin. Lateral-line scales slightly higher than its width, gradually smaller and becoming narrower posteriorly; 3 or 4 pores on each side of lateral-line scales before dorsal fin.

Luminescent duct well developed at ventral abdomen cavity, originating from below opercle and divided into two branches from its origin to anus.

Coloration. Body translucent when fresh, creamy white when preserved. Chromatophores present around the orbital, frontal, and nape regions; fine black stripes on cheek. Anterior three-fourths of upper jaw and entire lower jaw covered with dense chromatophores. Upper fourth of body with dense grayish chromatophores, not extending downward to lateral line ventrally. No chromatophores on lateral-line. Bases of dorsal-, pelvic-, and anal- fin rays with black pigments. Scattered chromatophores on upper rays of pectoral fin, absent on the rest rays. Broad black margins on abdomen ridge. Lateral sides of tail (behind anus) mostly blackish in specimen> 200 mm. Surface of cleithrum blackish; gill chamber, tongue, gill arches, and inner side of gill cover blackish. Scattered black chromatophores on branchiostegeal rays; branchiostegal membranes clear without pigments.

Size. A small species with adults reaching 249 mm SL.

Etymology. The specific name is derived from niger, means black and ventral means lower part of body, in referring the broad margin on abdomen ridge.

Distribution. Known from Taiwan and Japan; maybe widespread in the northwestern Pacific Ocean. In Taiwan, most specimens were collected by midwater trawl together with Sakura shrimp ( Lucensosergia lucens ) and other pelagic fishes, such as Bregmaceros spp. and myctophids.

Ecology. All specimens were collected by midwater trawl from surface to less than 100 meters; which suggests that this is a mesopelagic species and may have diurnal vertical migration. Some individuals are found to have myctophids or other fishes inside the stomach which suggests that the species feeds on fishes rather than sakura shrimps.

Comparison. Lestrolepis nigroventralis sp. nov. shares with Ll. intermedia from the western Atlantic Ocean in similar body proportion, fin formula, vertebral formula, and coloration. It can be distinguished from the later by having 32–35 (vs. 28–29) prehaemal vertebrae; 33–35 (vs. 30–32) prepelvic vertebrae; 43–46 (vs. 42–44) predorsal vertebrae; 53–57 (vs. 50–53) predorsal vertebrae; 75–81 (vs. 73–75) lateral-line scales, and a different COI gene sequence (K2P distance=0.063).

Although both species have their DFO at about midline of space between VFO and AFO, the DFO is usually slightly before the midline of V–A (V–D 47.6–55.0% of V–A) in Ll. nigroventralis ( Fig. 3A ), whereas the DFO is always slightly behind midline of V–A (V–D 51.4–59.5% of V–A) in Ll. intermedius ( Fig. 3B ). Uyeno et al. (1983) also mentioned their Atlantic specimens (n=11, 189– 234 mm SL) have the V–D 11.8–13.8% SL, which agrees with our data (11.2–15.2%); whereas that of Ll. nigroventralis sp. nov. is clearly smaller (9.8–11.7% SL).

Lestrolepis nigroventralis can be easily separated from Ll. Japonica which has the DFO clearly before middle of V–A (V–D 32.5–43.1% of V–A) ( Fig. 3A vs. 3C), narrow rows of black dots with pale margin or very narrow black margin on abdomen ridge, different numbers of anal-fin rays and different lateral-line and vertebral formulae ( Tables 1–6 ). Although previously including under the junior synonym of Lestrolepis luetkeni (Ege, 1933) , Ll. pofi is recognized as a valid species herein which differs from Ll. nigroventralis by having 32–36 anal-fin rays and 82–89 total vertebrae ( Ho & Golani, 2019).

Figures

FIGURE 1. Lestrolepis nigroventralis sp. nov. A, B. NMMB-P28481, holotype, 234 mm SL. A. fresh, photo by K. Koeda. B. preserved. C. NMMB-P27930, paratype, 244 mm SL, fresh. D. NMMB-P27941, paratype, 228 mm SL, fresh.

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.