Bothus myriaster (Temminck & Schlegel, 1846)

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 170-172

Bothus myriaster (Temminck & Schlegel, 1846)

Oval flounder; ạƖľ

Figures 3 C–F; Table 4

Rhombus myriaster Temminck & Schlegel, 1846:181 (Type locality: Nagasaki Prefecture, Japan).

Bothus ovalis: Norman, 1927:32 (in part); Chen & Weng, 1965:56.

Bothus myriaster: Chabanaud, 1929:379 ; Chen & Weng, 1965:54; Shen, 1983:21; Shen in Shen et al., 1993:567; Shen & Wu, 2012:749.

Bothus assimilis :? Chen & Weng, 1965:57;? Shen & Wu, 2012:749.

Specimens examined. NMMB-P02769 (1 male, 102.5), Chieh-din, Kaohsiung, 50 m, bottom trawl, 1 Nov. 2001 ; NMMB-P04164 (3 males, 170.6–177.3), Kaohsiung, 11 Oct. 1965 ; NMMB-P12210 (1 male, 154.0), Daxi , Yilan, 22 Jan. 2010 ; NMMB-P22243 (5, 73.4–123.9), Ke-tzu-liao, 9 Mar. 2015 ; NMMB-P23231 (4 males, 1 female, 103.5– 113.8), Ke-tzu-liao, 31 Mar. 2016 ; NMMB-P23285 (1 male, 118.4), Ke-tzu-liao, 7 Apr. 2016 ; NMMB-P23286 (2 males, 121.9–123.4), Ke-tzu-liao, 7 Apr. 2016 ; NMMB-P24769 (1 male, 1 female, 106.1–106.4), Dong-gang , 31 Mar. 2016 . More specimens deposited in NMMB-P.

Diagnostic Features. D 89–97; A 65–77; P 9–11; C 2–3+11–13+2–3=17; LLs 79–105; GR 0–5+5–8=9–11; vert. 10+26–29=36–39.

Body very compressed, and round to elliptical, changing ontogenetically, greatest depth at middle part of body (51.8–76.6% SL). Head much shorter than half of body depth (21.8–27.8% SL); upper profile of head with distinct concavity anterior of dorsal margin of upper eye, steep in both sexes. Snout much shorter than eye diameter. Rostral spine present on tip of snout in males, absent in females and juveniles. Eye diameter subequal to upper jaw. Small orbital spine at anterior margins of each eye in males, absent in females and juveniles; large males with broad flap at hind margins of eyes. Interorbital space with shallow and broad concavity, its width wider in males than in females and juveniles.

Mouth small, upper-jaw length 6.0–7.5% SL; maxilla extending to or slightly beyond anterior margin of lower eye; low and obtuse knob on symphysis of lower jaw in males. Teeth on upper jaw biserial, those on outer series stronger and more wide-spaced than those on inner series; teeth on lower jaw biserial in anterior section, uniserial in posterior section. Gill rakers on lower limb, short and slender, pointed at tip, not serrate; those on upper limb very small or rudimentary. Scales on ocular side very small, cycloid except for those on dorsal and ventral margins of body, cycloid on blind side. Pectoral-fin rays elongate on ocular side in both sexes, longest ray 42.1–65.7% SL.

Coloration. Ocular side of body uniformly darkish brown with many dark spots; a dark blotch above junction of curve and straight section of lateral line; a dark blotch on middle of straight section of lateral line; dorsal and anal fins with a series of dark spots; posterior 1/3 of caudal fin blackish. Blind side of body white on front half of body; darker on posterior half with several dark cross bars, clear and dark in males, faint or missing in juveniles and females.

Size. Reaching 201 mm SL in Taiwan; up to about 270 mm TL elsewhere ( Hensley & Amaoka, 2001).

Distribution. Widespread around Taiwan; Indian to Western Pacific oceans ( Amaoka, 2016).

Remarks. Body form changes from round to elliptical with growth ( Amaoka, 1964). Specimens larger than 70 mm SL exhibit a distinct sexual dimorphism, including changes of the interorbital width, presence of rostral and orbital spines on the lower eye, orbital flaps at hind margins of eyes, and body coloration on the blind side.

Figures

FIGURE 3. A–B. Bothus mancus, NMMB-27812, female, 149.9 mm SL. C–F. B. myriaster, NMMB-P23231, male, 103.5 mm SL (C–D) and female, 107.6 mm SL (E–F). G–H. Bothus pantherinus, NMMB-P23285, male, 116.5 mm SL. Left column, ocular side and right column, blind side.