Crossorhombus valderostratus ( Alcock, 1890 )

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 182-183

Crossorhombus valderostratus ( Alcock, 1890)

Victory bluespotted flounder; xühḃľ

Figures 6 C–F; Table 6

Rhomboichthys valde-rostratus Alcock, 1890:435 (Type locality: Sri Lanka).

Crossorhombus valde-rostratus: Norman, 1927:28 .

Crossorhombus valderostratus: Hensley & Randall, 1993:1125 .

Crossorhombus kobensis: Shen, 1983:18 , fig. 23.

Specimens examined. NMMB-P22286 (5 males, 4 females, 51.3–70.7), Ke-tzu-liao, 28 Mar. 2015; NMMB- P25675 (6 females, 65.2–73.3) , NMMB-P25712 (3 males, 60.1–70.5), Ke-tzu-liao, 27 Jun. 2016. More specimens deposited in NMMB-P.

Diagnostic features. D 82–88; A 62–68; P 10–12; C 2+13+2=17; LLs 46–55; GR 0(1)+6–7=6–7; vert. 10+23– 25=33–35.

Body short and deeply ovate, greatest depth slightly before middle part of body (54.4–63.2% SL). Head much shorter than half of body depth (24.5–27.4% SL); upper profile of head with deep concavity anterior of upper margin of lower eye; head profile steep, almost vertical in mature males, less steep in females and juveniles. Snout much shorter than eye diameter. Rostral spine on tip of snout, sharp and strong in males, absent in females and juveniles. Eyes diameter slightly shorter than upper jaw. Small orbital spines at anterior margin of both eyes in males, absent in females and juveniles. Interorbital space deeply and widely concave, its width wider in males than in females and juveniles.

Mouth small and lipped, upper-jaw length 6.8–7.9% SL; maxilla extending to slightly beyond anterior margin of lower eye. Teeth on upper jaw biserial, those on outer series larger and more widely spaced than those on inner series; teeth on lower jaw uniserial, similar to inner teeth of upper jaw. Gill rakers on lower limb short and blunt, not serrate; absent on upper limb. Scales on ocular side small, ctenoid with long ctenii on posterior margin; scales on blind side cycloid. Pectoral-fin rays on ocular side filamentous in males, pectoral-fin length 32.6–41.9% SL in males, 19.7–24.7% SL in females.

Coloration. Ocular side of body dark to light brown with many dark spots and obtuse dark blotches; faint large dark blotch on curve and middle of straight section of lateral line; surface of eyes with many dark spots; margins of dorsal and anal fins not dark; blind side of body in males with distinct deep-bluish pattern in horizontal V-shape, uniformly whitish in females.

Size. Reaching 104 mm SL in Taiwan, up to 121 mm SL known from Kenya ( Hensley and Randall 1993).

Distribution. Southern Taiwan; widespread in Indian and West Pacific oceans ( Amaoka, 2016).

Remarks. Specimens more than about 60 mm SL exhibit a distinct sexual dimorphism in respect to the interorbital width, presence of rostral and orbital spines at both eyes, the pectoral-fin length on the ocular side and body coloration on the blind side. Crossorhombus valderostratus very closely resembles C. howensis from Lord Howe Islands and Taiwan, but it differs from latter in having longer pectoral fins on the ocular side in males (32.6–41.9% SL, vs. 27.8–31.8), and a filamentous second ray of the pectoral fin.Also, C. valderostratus inhabits in deeper water than C. howensis .

Figures

FIGURE 6. A–B. Crossorhombus kobensis, NMMB-P22249, male, 69.1 mm SL. C–F. C. valderostratus, NMMB-P22286, male, 70.7 mm SL (C–D) and female, 66.2 mm SL (E–F). G–H. Grammatobothus polyophthalmus, NMMBA 28527, 116.9 mm SL, photo by K. Koeda.