Enneapterygius velatus Tashiro, Senou et Motomura, 2018

English name: sail triplefin Table 1; Figs 1, 2, 3, 4, 5

Material examined.

KAUM –I.220189 (Fig. 1), female, 19.7 mm SL, off Midara-hama Beach, Iriomote Island, Yaeyama Islands, Okinawa, Japan, 24°22'23"N, 123°44'49"E, hand net, 18 m depth, 30 Aug. 2025, M. Sato leg.

Description.

Dorsal profile of snout slightly rounded. Mouth oblique; posterior margin of maxilla reaching vertically below eye center; anterior tip of upper jaw almost level with lower margin of pupil (lateral view). Medial supratemporal canal strongly curved (U-shaped), with two short branches. Anterior nostril a membranous tube, at mid-eye level, closer to eye than to upper lip; nasal tentacle unbranched, broad, and rounded distally; posterior nostril opening circular, without membranous tube. Eye oriented dorsolaterally, with broad elliptical tentacle slightly longer than nasal tentacle, on posterodorsal margin. Interorbital space narrow, its width less than pupil diameter. Opercular margin slightly rounded, reaching vertically below posterior end of first dorsal-fin membrane. Body slender, slightly compressed anteriorly, progressively more compressed posteriorly.

First dorsal extremely long; 1 st and 2 nd spines elongate, filamentous, gradually thinning distally; membrane between 1 st and 2 nd spines irregularly incised, forming three branches, two rounded (blunt) and one pointed; dorsal fin origin vertically above pre-opercular margin; length of first dorsal-fin base very short, it length less than half distance between base of 3 rd spine of first dorsal fin and second dorsal fin origin; first dorsal-fin spine base with well-developed inclinator muscles. Origin of second dorsal fin just above 4 th pored lateral-line scale, 3 rd spine longest, spines thereafter becoming gradually shorter posteriorly, forming rounded margin. Third dorsal fin triangular, its origin just above 10 th scale of lateral line posterior series. Anal-fin membranous margin uniformly incised between rays; anal fin origin just below 6 th spine base of second dorsal fin, its posteriormost tip close to caudal-fin base. Pectoral fin pointed posteriorly, 9 th soft ray longest, its tip reaching below posterior edge of second dorsal fin; upper and lowermost pectoral-fin base below horizontal level of posterior tip of opercular and posteriormost origin of first dorsal fin membrane, respectively. Pelvic fin long, 2 nd ray extending slightly beyond base of 1 st spine of anal fin (right side; 2 nd ray on left side damaged); pelvic fin origin vertically below base of 1 st spine of first dorsal fin. Caudal fin truncate, its length less than head length.

Lateral line discontinuous, with anterior series of pored scales (two posteriormost notched) and posterior series of notched scales; anterior series ending below midpoint between bases of 7 th and 8 th spines of second dorsal fin; posterior series beginning below first notched scale in anterior series, ending at caudal-fin base; one scale row between anterior and posterior series. Body scales peripheral ctenoid; scales absent on head (including maxilla, interorbital space, preopercle, and opercle), pectoral-fin base, pre-dorsal and pre-pelvic fin regions, and all fin membranes, except basal part of caudal fin. Ctenii on body scales becoming fewer and more sparce toward ventral surface; inter-pelvic-fin region and abdomen scales cycloid (Fig. 2).

Fresh coloration of female.

(Fig. 1 A). Dorsal profile of head, including snout, greenish; cheeks white with oblique orange markings. Iris black, with scattered tiny yellowish blotches; pupil black, margined by orange; orbital tentacles pale orange. Anterior nostril tube and tentacle whitish. Body uniformly translucent, whitish; scales on dorsal half of body generally margined by orange, forming four indistinct saddles with melanophores; ventral surface of body with four faint blackish bands vertically, continuous with irregular black lines on anal fin; small whitish blotches on mid-lateral longitudinal scale row, each associated with scattered tiny yellow dots. Small indistinct black blotch before anus. First dorsal fin orange-mottled, membrane between third spine and body transparent white. Second and third dorsal fins transparent white with orange rays and spines; scattered white dots forming three irregular oblique bands on membranes; two black blotches on upper edge of second dorsal fin. Pectoral fin translucent, whitish with orange rays, pale yellow basally, lower half with three faint orangish bands; pectoral fin base with scattered white blotches, two orange oval blotches anteroventrally. Pelvic fin white, orangish basally. Anal fin with faint blackish bands, overlain by orange pigment on rays. Caudal peduncle with numerous melanophores, forming triangular pigmentation on caudal-fin base. Caudal fin transparent white with orange rays; two faint curved white bands on caudal fin base and middle part of caudal fin.

Preserved coloration of female.

(Fig. 1 B). Almost all pigmentation completely lost, although blackish pigmentation still present, particularly on second dorsal and anal fins, and caudal fin base. Dorsal surface of head pinkish. Longest (9 th) ray of pectoral fin with three brownish blotches, evenly placed along ray.

Live coloration of female.

(Fig. 3 A). Living and fresh coloration similar, but whitish pigmentation more distinct in former. Orange saddles on lateral body surface less visible in life. Dorsum of head with scattered black blotches.

Distribution and habitat.

Enneapterygius velatus has previously been recorded from Kume (type locality) and Amami-oshima islands (Ryukyu Islands) (Tashiro et al. 2018; Fig. 4), with underwater photographs confirming the occurrence of the species on Okinawa and Sesoko islands (Okinawa Islands), Japan and New Britain, Papua New Guinea (KPM-NR 80765; Kato 2014; Tashiro et al. 2018; Allen and Erdmann 2024). The presently reported specimen represents the first record of the species from Iriomote Island, and the third specimen-based record of the species.

Although previous authors reported E. velatus from depths between 30–41 m on relatively deep reefs (Kato 2014; Tashiro et al. 2018), the single specimen described herein was collected at a depth of 18 m, after having been observed on the surface of a rock covered by sea sponge, on a sandy and coral-rubble bottom (Fig. 3 B).

Remarks.

The single specimen collected from Iriomote Island (KAUM –I.220189) possessed the following characteristics of the Enneapterygius tutuilae species group, defined by Fricke (1997), Holleman and Bogorodsky (2012), Tashiro et al. (2018), and Fricke et al. (2024), and followed herein: body relatively small; all pectoral fin rays unbranched; first dorsal fin significantly long in both sexes; orbital tentacle unbranched, broad; and mandibular pore formula usually 2 + 2 + 2. Additionally, the morphometric and meristic characters of the present specimen agreed closely with the original description of Enneapterygius velatus provided by Tashiro et al. (2018) (Figs 1, 2; Table 1). Enneapterygius velatus clearly differs from all other congeners, including the six members of the E. tutuilae group, viz., Enneapterygius pusillus Rüppell, 1835; Enneapterygius tutuilae Jordan et Seale, 1906; Enneapterygius altipinnis Clark, 1980; Enneapterygius mirabilis Fricke, 1994; Enneapterygius kosiensis Holleman, 2005; and Enneapterygius rubrimarginatus Fricke, Erdmann et Ichida, 2024, by having the following characters: first dorsal fin extremely long, its length 31.6 % – 34.6 % of SL; first dorsal-fin base short, its length less than half distance between base of 3 rd spine of first dorsal-fin and second dorsal-fin origin; well-developed inclinator muscles present on basal part of first dorsal fin; pelvic fin long, its posterior tip extending beyond anal fin origin; medial supratemporal canal U-shaped; snout profile slightly rounded; abdomen from pelvic fin insertion to anus covered by small cycloid scales; caudal fin base with blackish pigmentation (Holleman and Bogorodsky 2012; Tashiro et al. 2018; Fricke et al. 2024; this study). It should be noted that although Fricke et al. (2024) treated Enneapterygius ventermaculus Holleman, 1982 as a member of the E. tutuilae group, this study confirmed that that nominal species differs from other members of the group in the following characters: five pectoral fin rays unbranched (all unbranched in the remaining six species in the E. tutuilae group); mandibular pore formula 3 + 1 + 3 (2 + 2 + 2); and first dorsal fin short in females (long in both sexes) (Holleman and Bogorodsky 2012; Holleman 2022; Fricke et al. 2024; this study).

In addition to the morphological characteristics, the genetic analysis in this study clearly separated E. velatus from E. tutuilae, co-occurring in Japanese waters. Each species formed a distinct clade on the maximum likelihood phylogenetic tree, based on 561 bp COI sequences (Fig. 5). Using the Kimura 2 - parameter model (Kimura 1980) with gamma distribution, the genetic distance between E. velatus, and E. tutuilae was estimated as 25.3 % – 28.4 %, respectively. However, to analyze the phylogenetic position of E. velatus within the E. tutuilae group necessitates sequence data for the remaining five species, including the morphologically most similar species E. mirabilis.

Comparative materials examined.

Enneapterygius tutuilae, 7 specimens, 13.4–19.1 mm SL, all collected from Japan, used for genetic analysis. KAUM –I.70986, female, 17.8 mm SL, off Chabana, Yoron Island, Amami Islands, 27°03'38"N, 128°24'32"E, 9 m depth, 15 Mar. 2015, S. Tashiro; KAUM –I.127653, male, 13.4 mm SL, Isso, Yaku-shima Island, Osumi Islands, 30°27'35"N, 130°29'17"E, 10 m, 3 Feb. 2019, K. Fujiwara; KAUM –I.170159, male, 19.1 mm SL, same locality as KAUM –I.127653, 10–20 m, 8 July 2022, K. Fujiwara and M. Sato; KAUM –I.179107, male, 14.3 mm SL, Sanju Bay, Iwo Island, Osumi Islands, 30°47'36"N, 130°16'11"E, 15–30 m, 6 Jan. 2023, S. Dewa et al.; KAUM –I.184122, male, 19.3 mm SL, same locality as KAUM –I.127653, 10 m, 22 May 2023, S. Harazaki et al.; KAUM –I.184140, male, 14.4 mm SL, KAUM –I.184142, female, 17.9 mm SL, Motoura Beach, Yaku-shima Island, 30°27'15"N, 130°29'52"E, 2–3 m, 21 May 2023, S. Harazaki et al.; Enneapterygius velatus: KPM-NI 6763, holotype, male, 22.4 mm SL, northeast of Kume Island, Okinawa Islands, Japan, 55 m, 31 July 1999, T. Kawamoto.