Tosarhombus octoculatus Amaoka, 1969

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 210-211

Tosarhombus octoculatus Amaoka, 1969

Eighteyed flounder; Āṯ±ãľ

Figures 10 D–E; Table 12–13

Tosarhombus octoculatus Amaoka, 1969:129 , fig. 36 (Type locality: Urado, Kochi Prefecture, Japan). Ho et al, 2009:7; Shen & Wu, 2012:755.

Specimens examined. NMMB-P02359 (1 male, 111.0), Taiwan, 30 May 1983 . Other localities: FAKU29431 (holotype, male, 161.8), Urado , Kochi Prefecture, Japan 20 Nov. , 1958; FAKU 29432–29438 (paratypes, 7 males 123.2–147.5), Urado , Kochi Prefecture, Japan, Nov. 20–24, 1958 ; FAKU 29439–29454 , (paratypes, 6 females, 90.5–143.4), Urado , Kochi Prefecture, Japan, 20–24 Nov., 1958 ; FAKU 33830 (paratype, 1 female, 129.5), Urado , Kochi Prefecture, Japan, 12 Dec. , 1959.

Diagnostic features. D 104 (96–104 from other localities); A 78 (76–82); P 13 (12–13); C 2+13+2=17 (2+13+2=17); LLs 66 (59–66); GR 0+7=7 (0+6–8=6–8); vert. 10+29=39 (10+28–30=38–40). Description based on a single specimen collected from Taiwan with additional information from other specimens shown in parentheses.

Body ovate, deepest at anterior 1/3 of body, its depth 50.0% SL (45.4–50.7% SL, from other localities). Caudal peduncle narrow, its depth about 10.4 (9.4–11.1)% SL. Head rather small 26.0 (25.1–27.8)% SL; upper profile of head with distinct concavity in front of dorsal margin of upper eye. Snout round, short, its length much shorter than eye diameter. Short obtuse rostral spine on tip of snout in males, (absent in females and juveniles from other localities). Eye diameter about equal to upper jaw length. Short and low orbital spine anterior of upper eye in males, (absent in females and juveniles). Interorbital space broad and shallow concave, its width about equal to eye diameter, 8.8% SL (9.1–12.9 in males, 4.2–8.3 in females), (wider in males than in females and juveniles).

Mouth large, upper-jaw length 7.9 (7.8–8.9)% SL; maxilla extending to middle of lower eye. Prominent knob on mandibular symphysis. Teeth on upper jaw small, biserial, those on outer row much shorter and widely spaced than those on inner row; teeth on lower jaw uniserial and close-set. Gill rakers only on lower limb, moderately long, pointed at tip, and not serrated, absent on upper limb. Scales small, ctenoid with long ctenii on ocular side; cycloid on blind side. Pectoral fin on ocular side moderately large, and elongate in males, its length 26.5% SL (22.4–31.4 in males, 18.5–20.4 in females and juveniles).

Coloration. Ocular side of body uniformly bluish purple; 6 yellowish white blotches with black rims on anterior margin of head; body on blind side milky white.

Size. Reaches 111.0 mm SL in Taiwan; up to 162 mm SL ( Amaoka, 1969).

Distribution. Western Taiwan; southern Japan to Philippines ( Amaoka, 2016).

Remarks. This species exhibits sexual dimorphism and ontogenetic changes of the interorbital width, the length of the pectoral fin on the ocular side, and the presence or absence of a rostral spine. Amaoka & Rivaton (1991) reported larvae of T. octoculatus from the Ryukyu Islands and eastern Taiwan. Ho et al. (2009) recorded a single adult male specimen from Taiwan. Photos of two large individuals collected from Penghu (Pescadores) Islands were also examined, but might now be lost.

Figures

FIGURE 10. A–C. Taeniopsetta ocellata, FRIP01118, 160 mm SL, ocular side (A) and blind side (B), photo taken by S.-C. Chaung; C. NMMB-P29264, 65.7 mm SL, juvenile. D–E. Tosarhombus octoculatsus, ca. 200 mm SL, specimen not retained.