Arnoglossus japonicus Hubbs, 1915

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 158-160

Arnoglossus japonicus Hubbs, 1915

Japanese lefteye flounder; ıƾ¥6ľ

Figures 1 A–B; Tables 1–2

Arnoglossus japonicus Hubbs, 1915:454 (Type locality: south of Kyushu, Japan). Chen, 1969:214; Shen, 1984:450; Chen & Yu, 1986:817; Shen in Shen et al., 1993:566; Shen & Wu, 2012:747.

Arnoglossus polyspilus (not of Günther): Shen in Shen et al., 1993:567.

Arnoglossus elongatus (not of Weber): Chen & Weng, 1965:43; Chen & Yu, 1986:817.

Specimens examined. NMMB-P02249 (1 male, 1 female, 118.7–121.6), Taiwan, 20 Jun. 1983 ; NMMB-P22222 (1 male, 1 female, 90.3–109.4), Ke-tzu-liao, 11 Feb. 2015 ; NMMB-P23187 (2 males, 2 females, 100.2–121.0), Ke-tzu-liao, 18 Mar. 2016 ; NMMB-P23207 (1 female, 116.9), Dong-gang , 5 Mar. 2016 ; NMMB-P23315 (3 males, 2 females, 110.0–110.1), Ke-tzu-liao, 18 Mar. 2016 ; NMMB-P24852 (2, 112.5–145), Ke-tzu-liao, 4 Apr. 2015 ; NMMB-P25680 (1 female, 130.8), Ke-tzu-liao, 27 Jun. 2016 ; NMMB-P25707 (1 male, 115.1), Ke-tzu-liao, 2 Apr. 2015 ; NMMB-P25709 (1 male, 105), Ke-tzu-liao, 27 Feb. 2017 . More specimens are deposited in NMMB-P.

Diagnostic features. D 100–108; A 77–84; P 12–14; C 3+11+3=17; LLs 66–72; GR 0+7–8=7–8; vert. 10+33– 34=43–44.

Body elongated, greatest depth near anterior 1/3 part of body (33.9–41.1% SL). Head small, its length about 66–74% of body depth (24.3–28.5% SL); front of head with slight concavity in front of upper eye; head profile gentle, same in both sexes. Snout sharply protruding, snout length shorter than eye diameter. Rostral spine absent on tip of snout in both sexes. Eye diameter slightly longer than 1/2 of upper-jaw length; upper eye about half eye diameter away from dorsal margin of head. No orbital spines in both sexes. Interorbital space with narrow bony ridge extending from anterior margin of lower eye to posterior space between both eyes.

Mouth large, upper-jaw length on ocular side 9.9–12.8% SL; anterior tip of upper jaw on about same vertical line to anterior tip of lower jaw; maxilla extending to or slightly beyond middle part of lower eye. Teeth on both jaws uniserial, upper jaw with 2–4 canine-like teeth on ocular side, 4–5 on blind side anteriorly, posteriorly gradually getting smaller; lower jaw with 8–16 widely spaced canine-like teeth. Gill rakers on lower limb, short and strong bearing 2–5 sharp spines on inner margin; entirely absent on upper limb.

Scales rather large and deciduous, cycloid on both sides. Second dorsal-fin ray elongate in males (2.7–3.5 in HL); no elongate ray in females. Pectoral fin on ocular-side short and feeble, about half of head (13.1–16.5% SL); that of blind side very short. Caudal fin round, uppermost and lowermost 3 rays simple, and middle rays deeply branched.

Coloration. Ocular side of body uniformly pale brownish without distinct blotches or spots; dorsal and anal fins uniformly pale brownish sometimes with darkish spots; blind side of body uniformly milky white.

Size. Reaching 131 mm SL in Taiwan; up to 144 mm SL in southern Japan ( Amaoka, 1969).

Distribution. Northeastern, western and southern Taiwan; Indian and Western Pacific oceans ( Amaoka, 2016).

Remarks. This species resembles A. yamanakai in having an elongate second dorsal-fin ray in males and similar counts of D and A, but differs in having cycloid scales on the ocular side, 10 abdominal vertebrae (vs. 11–12 in the latter), a long upper jaw (2.15–2.48 in HL, vs. 2.54–2.92), uniserial teeth on the upper jaw (vs. biserial), longer gill rakers, and no black margin of the anterior half of the dorsal fin.

Chen & Weng (1965) recognized two lots (THUP 2602, 2814) with 4 specimens of A. elongatus . The whereabouts of these specimens are unknown. However, Chen (1969) mentioned that their specimens were misidentification of the present species.

Figures

FIGURE 1. A–B. Arnoglossus japonicus, NMMB-P23187, male 121.0 mm SL (A) and female, 110.2 mm SL (B). C. A. macrolophus, NMMB-P 23204, male, 81.1 mm SL. D–E. A. oxyrhynchus, NMMB-P23317, male, 148.0 mm SL (D) and female, 171.1 mm SL (E). F. A. polyspilus, NMMB-P29041,164 mm SL. G. A. tenuis, NMMB-P25684, 64.5 mm SL. H. A. yamanakai, NMMB-P25685, 95.0 mm SL.