Engyprosopon maldivense ( Regan, 1908 )

Amaoka, Kunio & Ho, Hsuan-Ching, 2018, Review of the genus Engyprosopon Günther, 1862 (Pleuronectiformes: Bothidae) from waters off Taiwan, with descriptions of two new species, Zootaxa 4413 (3), pp. 449-481 : 461-464

Engyprosopon maldivense ( Regan, 1908)

Figures 8–9 ; Table1

Scaeops maldivensis Regan, 1908:234 , pl. 25, fig. 1 (type locality: Maldives, Indian Ocean , depth 27–44 fathoms [49.3–80.5 m]).

Engyprosopon maldivensis: Norman, 1934:216 , fig. 165; Amaoka et al., 1993:393, fig. 8; Hensley & Amaoka, 2001:3832; Shao et al., 2008:264; Shen & Wu, 2012:751, 1 fig.

Arnoglossus maculipinnis Fowler, 1934: 329 , fig. 84 (type locality: Vicinity of Jolo , Sulu Province, Philippines, 6°08'45"N, 121°03'E, depth 20–76 fathoms [36.6–139 m]).

Engyprosopon borneensis Chabanaud, 1948:64 , fig. 1 (type locality: Northeast of Datoe [Datoae] Point, north coast of Borneo).

Engyprosopon macroptera Amaoka, 1963:115 , fig. 5 (type locality: Mimase, Kochi Prefecture, Japan). Amaoka, 1969:154, fig. 52; Shao et al., 2008:264; Ho et al., 2009:10; Shen & Wu, 2012:751, 1 fig.

Engyprosopon filimanus (not of Regan, 1908): Chen & Weng, 1965:49, fig. 33.

Material examined. NMMB-P2053, male, 113.5 mm SL, date unknown; NMMB-P2771, male and 2 females, 76.1–83.0 mm SL, Chie-din, 50 m, 1 Nov. 2001; NMMB-P6695, male, 180.5 mm SL, 11 Oct. 1965; NMMB- P22226, 3 males, 112.7–151.6 mm SL, Ke-tzu-liao, 11 Feb. 2015; NMMB-P22238 , 4 females, 83.2–102.7 mm SL, Ke-tzu-liao, 12 Mar. 2015; NMMB-P22254 , sex unknown, 71.1 mm SL, Ke-tzu-liao, 21 Jan. 2015; all collected from Kaohsiung, southwestern Taiwan .

Diagnosis. Caudal fin without black blotches; ocular-side pectoral fin with greatly elongate filament in both sexes; gill rakers not serrate; upper jaw teeth biserial.

Description. Dorsal-fin rays 85–94, anal-fin rays 64–69, ocular-side pectoral-fin rays 10–12, blind-side pectoral-fin rays 9–11, caudal-fin rays 3 + 11 + 3; ocular-side pelvic-fin rays 6, blind-side pelvic-fin rays 6, scales in lateral line 44–48, gill rakers 0–3 + 8–11, vertebrae 10 + 25–26.

In SL: HL 3.68–4.42, body depth 1.82–2.10. In HL: snout 3.78–5.20, upper eye diameter 3.12–3.96, lower eye diameter 3.09–4.16, interorbital width 1.65–2.31 in males, 2.72–3.89 in females, ocular-side upper jaw 2.59–2.77, blind-side upper jaw 2.56–2.78, ocular-side lower jaw 1.95–2.18, blind-side lower jaw 1.99–2.18, caudal peduncle depth 1.74–2.13, ocular-side pectoral fin 0.43–0.61, blind-side pectoral fin 1.56–2.00, ocular-side pelvic fin 1.73– 2.33, blind-side pelvic fin 1.85–2.72, base of ocular-side pelvic fin 2.05–2.42, base of blind-side pelvic fin 5.52– 7.25, longest dorsal fin ray 1.55–1.98, longest anal fin ray 1.44–2.00, middle caudal fin ray 0.86–1.12.

Body moderately ovate, deepest slightly anterior to vertical through middle of body; body depth usually more than 1/2 of SL; dorsal and ventral contours of body nearly symmetrical with gradual taper posteriorly. Caudal peduncle subequal to, or less than, 1/4 of body depth. Head small, its length about 1/4 of SL; upper profile of head with small concavity slightly anterodorsal to upper margin of lower eye, very steep, almost vertical in mature males, not so in females and juveniles. Snout rather long, slightly protruding, shorter than eye diameter. Rostral spine present on both sides of snout in males; ocular-side spine stronger than that on blind side; rostral spine absent or feeble in females and juveniles. Eyes large, eye diameter shorter than upper jaw length, lower eye in advance of upper eye. No orbital spine in either sex. Interorbital space widely concave, distinct sexual and ontogenetic differences in width, interorbital width wider in males than in females. Ocular-side nostrils anterior to upper margin of lower eye; anterior nostril a longer tube than that of posterior nostril; blind-side nostrils closely set below origin of dorsal fin, very small.

Mouth rather large, oblique; maxilla extending to vertical through anterior 1/3 of lower eye; anterior tip of upper jaw distinctly beyond tip of lower jaw, when mouth closed; small knob at mandibular symphysis. Teeth on upper jaw biserial, those in outer series larger, more widely spaced and sparse compared with those in inner series, some canine-like teeth anteriorly, protruded before tip of lower jaw; lower jaw teeth uniserial, conical, nearly same size as anterior teeth of upper inner series. Gill rakers on first arch slender; inside edge not serrate, but covered by skin with tiny hairs; no or few rudimental gill rakers on upper limb. Ocular-side scales ctenoid with short ctenii, large and deciduous; tips of both jaws and of ocular side of snout naked; scales cycloid on blind side of body.

Dorsal and anal fins without elongate rays. Ocular-side pectoral fin with elongate filamentous rays in both sexes; elongate ray about 1.2–2.3 times of head length; blind-side pectoral-fin rays not elongate. Ocular-side pelvic-fin origin at tip of isthmus, ocular-side fifth ray opposite to blind-side first ray. Tip of isthmus near vertical line through middle of lower eye. Caudal-fin rays branched, except for three upper- and three lowermost rays. Tip of pelvic bone not distinctly extruded.

Coloration in alcohol. Ocular side of body pale yellowish green; anterior margin of head anterior to both eyes with tiny black dots; one distinct black spot at middle of anterior margin of upper eye; sometimes with a black spot at posterior upper corner of lower eye, and one black spot at anterior and posterior parts, respectively. Blind side of body in males dark grey, except for pale yellowish white head; blind side of body of females uniformly yellowish white. All fins on ocular side uniformly semi-transparent, without special markings.

Sexual dimorphism. This species shows sexual dimorphism only in interorbital width, presence of a rostral spine, and coloration on the blind side of the body.

Distribution. Widespread in the Indo-West Pacific Ocean: southern Japan, Taiwan, South China Sea, Philippines, northwestern Australia, Coral Sea, and Maldive Islands. Bathymetric range 30–215 m, usually 30–75 m ( Amaoka et al., 1993). In Taiwan, it is commonly collected from depths less than 100 m.

Remarks. This species, characterized in lacking black botches on its caudal fin and in having an elongate pectoral fin on the ocular side in both sexes, was previously reported from waters off Taiwan as E. macroptera . Amaoka et al. (1993) synonymized this species with E. maldivense , previously known from the Maldives Islands, notwithstanding that E. maldivense has a wide range of meristic features with its geographic distribution.

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Figures

FIGURE 8. Engyprosopon maldivense (Regan, 1908). Ocular side, A. NMMB-P22226, male, 121.3 mm SL. B. NMMB- P22238, female, 102.3 mm SL.

FIGURE 9. Engyprosopon maldivense (Regan, 1908). Blind side, same specimens as those in Figure 8.