Crossorhombus kobensis, : Kuronuma, 1939

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 180-181

Crossorhombus kobensis ( Jordan & Starks, 1906)

Kobe flounder; àƾḃľ

Figures 6 A–B; Table 6

Scaeops kobensis Jordan & Starks, 1906:170 (Type locality: Kobe, Hyogo Prefecture, Japan).

Crossorhombus kobensis: Kuronuma, 1939:84 ; Shen, 1983:17 (in part); Shen in Shen et al., 1993:568; Shen & Wu, 2012:750.

Specimens examined. NMMB-P22249 (1 male, 69.1), Taiwan (possibly Dong-gang ), no other data. Other localities : FAKU15947 (1 female, 79.8) , FAKU15973 , 15980 (2 males, 67.1–99.0), Mimase , Kochi Prefecture, Japan 20 Feb. 1951 ; FAKU 25611 (1 male, 97.5), Yawatahama, Ehime Prefecture, Japan, 13 Mar. 1956 ; FAKU29821 (1 male, 103.5), Choshi, Chiba Prefecture, Japan 20 Jul. 1958 ; FAKU 29829–29830 (2 males, 79.3–81.2) , FAKU29834 , 29837–29838 , 29849 , 29851 (5 males, 50.5–74.0), Mimase , Kochi Prefecture, Japan, 23 May 1959 ; FAKU29866 , FAKU29876 , 29878 , 29879 , 29891–29892 , 29894 (7 females, 49.2–70.8), Mimase , Kochi Prefecture, Japan 23 May 1959 .

Diagnostic features. Description based on a single specimen collected from Taiwan, with additional information from other specimens. D 85 (80–86 from other localities); A 64 (60–67); P 11 (10–11); C 3+11+3=17; LLs 56 (50–55); GR 0+6=6 (0+6–7); vert. 10+25=35 (10+24–26=34–36).

Body ovate, strongly compressed, greatest depth at middle part of body 54.1% SL (49.3–56.8% SL, from other localities). Head much shorter than half of body depth 24.5% SL (23.1–27.3); 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, from other localities). Snout much shorter than eye diameter. Rostral spine on tip of snout, sharp and strong in males (absent in females and juveniles).

Eye diameter shorter than upper jaw. Some 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 females, 10.6% SL (5.9–12.3 in males, 2.0– 5.5 in females). Mouth small, upper-jaw length 6.8% SL (6.8–8.6); maxilla extending to 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, closely set. Gill rakers on lower limb very short and slender, 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, second ray longest, longer than head; pectoral-fin length 31.3% SL (30.8–57.2 in males, 22.2–36.1 in females).

Coloration. Ocular side of body uniformly dark brown with obtuse dark blotches on lateral line and a series of dark spots arranged along dorsal and ventral margins of body; many very tiny elliptical black spots arranged in front of eyes and interorbital space; margins of dorsal and anal fins dark; blind side of body in males stained distinctly deep bluish at posterior 2/3 portion, its anterior margin without concavity, uniformly whitish in females.

Size. Reaching 69 mm SL in Taiwan; up to 120 mm TL elsewhere ( Hensley & Amaoka, 2001).

Distribution. Western and southwestern Taiwan; Southern Japan, South China Sea, East China Sea ( Amaoka, 2016).

Remarks. Specimens larger than 50 mm SL exhibit a distinct sexual dimorphism expressed in the presence of rostral and orbital spines before both eyes and the coloration on the blind side.

Crossorhombus kobensis resembles C. valderostratus in having a large dark blue pattern on the blind side of the body in males, but it differs from the latter by a rather elliptical body, 3 unbranched upper and lower rays of the caudal fin and no concavity at the anterior margin of the blue pattern on the blind side of the body in males. This species is rare in Taiwan, but rather common in Japan ( Amaoka, 1969).

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.