Bothus mancus ( Broussonet, 1782 )

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 169-170

Bothus mancus ( Broussonet, 1782)

Tropical flounder; ăľ

Figures 3 A–B; Table 4

Pleuronectes mancus Broussonet, 1782 : no pagination (Type locality: Ulietea, near Anamoka, Tahiti).

Bothus mancus: Norman, 1927:34 ; Chen & Weng, 1965:58; Shen, 1983:24; Shen in Shen et al., 1993:567; Shen & Wu, 2012:749.

Specimens examined. NMMB-P00628 (female, 147.3), Taiwan, 7 Feb. 1985 ; NMMB-P04701 (male, 342.4), Hengchun, Pingtung, 15 Sep. 1965 ; NMMB-P05154 (female, 129.3), Wan-li-ton, Hengchun , Pingtung, 15 Sep. 1966 ; NMMB-P27812 (149.9), Hengchun, Pingtung, 17 Nov. 2017 .

Diagnostic features. D 99–101; A 77–79; P 11–13; C 2+13+2=17; LLs 81–89; GR 0+8–11=9–11; vert. 10+30=40.

Body compressed; body shape changed ontogenetically, from round to elliptical, greatest depth at middle part of body (54.3–58.9% SL). Head length about equal to half of body depth (27.5–29.9% SL); upper profile of head with shallow, gentle concavity anterior of dorsal margin of upper eye, steep in both sexes. Snout much longer than eye diameter. Rostral spine present on tip of snout in males, absent in females and juveniles. Eye diameter less than half of upper jaw length. Males with 3–4 small orbital spines on anterior margin of upper eye and 1 strong spine on anterior margin of lower eye; both eyes in mature males with several flaps. Interorbital space shallow, wide and concave, its width wider in males than in females and juveniles.

Mouth large, upper-jaw length 9.1–10.1% SL; maxilla extending to or slightly beyond anterior margin of lower eye; large and obtuse knob on symphysis of lower jaw in males. Teeth on both jaws uniserial, somewhat enlarged anteriorly. Gill rakers only on lower limb, short and slender, pointed at tip, not serrate.

Scales on ocular side very small, ctenoid with moderate long ctenii on posterior margin, cycloid on blind side. Pectoral-fin rays on ocular side remarkably elongate in males, pectoral fin vary in length (20.9–65.7% SL).

Coloration. Ocular side of body uniformly darkish brown mottled with many dark spots; head and body with many small bluish spots and rings; a diffuse dark blotch above junction of curve and straight portions of lateral line; a darker blotch on middle of straight section of lateral line; a smaller blotch anterior to caudal peduncle; a series of dark botches along bases of dorsal and anal fins; pectoral fin on ocular side with irregular dark brown cross-bars. Blind side of body yellowish white.

Size. Reaching 342 mm SL in Taiwan; up to about 460 mm SL elsewhere ( Norman, 1934).

Distribution. Around Taiwan, including Penghu, Green and Orchid islands; widespread in the Indian and Pacific oceans ( Amaoka, 2016).

Remarks. This species inhabits in similar habitats as Bothus pantherinus , but differs from the latter in having a notch at the frontal margin of the head and higher meristics. Its body form changes from a round to an elliptical shape with growth.

Specimens larger than 220 mm SL exhibit a distinct sexual dimorphism in the interorbital width, the pectoral-fin length on the ocular side, presence of rostral and orbital spines on both eyes, and orbital flaps on both eyes.

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.

Tables

TABLE 4. Frequency of six meristic data of three Bothus species in Taiwan.

Dorsal-fin rays
	n	86	87	88	89	90	91	92	93	94	95	96	97	98	99	100	101
B. mancus B. myriaster B. pantherinus	4 20 20	1	0	4	3 3	2 4	4 3	2 4	3 1	2	1	1	2		2	1	1
Anal-fin rays
	n	65	66	67	68	69	70	71	72	73	74	75	76	77	78	79
B. mancus B. myriaster B. pantherinus	3 19 20	2	0	2 3	7 4	2 5	1 5	1 3	2	0	1	0	0	1 1	1	1
				Pectoral-fin rays											Vertebrae (precaudal + caudal)
	n	9	10	11	12	13						n	10	+	26	27	28	29	30
B. mancus B. myriaster B. pantherinus	4 20 20	12	7 14	1 1 5	1 1	1						3 20 20	3 20 20		1	2 7	15 12	2 1	3
Lateral-line scales
	n	77	78	79	80	81	82	83	84	85	86	87	88	89	90	91	92	//	102	103	104	105
B. mancus B. myriaster B. pantherinus	3 19 20	2	1	1 3	2 3	1 2 4	0 2 0	0 3 2	0 0 3	0 0 0	0 0 2	1 0	0 1	1 0	1	2	3	//	1	0	0	1
Gill rakers (upper + lower)
	n	0	1	2	3	4	5	+	5	6	7	8	9	10	11
B. mancus B. myriaster B. pantherinus	3 20 20	3 1 8	1 0	1 2	8 6	8 4	1		2	9 7	8 6	1 6	1 1	1	1