Eviota nigramembrana, Greenfield, David W. & Suzuki, Toshiyuki, 2013

Greenfield, David W. & Suzuki, Toshiyuki, 2013, Eviota nigramembrana, a new dwarfgoby from the Western Pacific (Teleostei: Gobiidae), Zootaxa 3637 (2), pp. 169-175 : 169-174

Eviota nigramembrana n. sp.

Blackbar dwarfgoby

Japanese name—Kometubu-isohaze Figs. 1–6 .

Eviota sp. C. Hayashi et al. 1990: 131; Senou et al., 2004: 122. Eviota sp. 3. Akihito et al. 2002: 1178.

Holotype. OMNH-P 35642, 13.9 mm female, Okinawa Prefecture, the Ryukyu Islands, Uehara, Iriomote-jima Island, 24.4325N, 123.8148E, 3–5 m depth, field number S-5671, Toshiyuki Suzuki & Masatomi Suzuki, 8 August 1996.

Paratypes: All from the Okinawa Prefecture, the Ryukyu Islands—USNM 406763 (ex OMNH-P 4285), 14.8 mm female, Aragusuku, Gusukube-cho, Miyako-gun, Miyako-jima Island, Aragusuku Beach, 24.7572N, 125.4263E, 3 m depth, field number S-3718, Toshiyuki Suzuki & Masatomi Hosokawa, 13 February 1994; OMNH-P 34238, 11.4 mm male, Uehara, Iriomote-jima Island, 24.4298N, 123.8262E, 7 m depth, field number S- 17076, Toshiyuki Suzuki, Masatomi Suzuki & Akira Kawai, 8 July 2008; OMNH-P 35639, 13.8 mm female, Uehara, Iriomote-jima Island, 24.4325N, 123.8148E, 5–6 m depth, field number S-3906, Toshiyuki Suzuki & Masatomi Suzuki, 22 August 1994; OMNH-P 35641, 14.1 mm male, Uehara, Iriomote-jima Island, 24.4325N, 123.8148E, field number S-3987, 7– 8 m depth, Toshiyuki Suzuki & Masatomi Suzuki, 27 August 1994; CAS 234537-(ex OMNH-P 35643), 14.0 mm male, Aakabanare, Iriomote-jima Island, 24.4004N, 123.8715E, 3 m depth, field number S-5983, Toshiyuki Suzuki & Masatomi Suzuki, 24 July 1997; OMNH-P 35644, 14.0 mm female, Uehara, Iriomote-jima Island, 24.4325N, 123.8148E, 5–6 m depth, field number S-6178, Toshiyuki Suzuki & Masatomi Suzuki, 29 July 1997.

Non-types: Philippine Islands -Negros Oriental, Siquijor Id.- USNM 223062 (3) 12.5–17.2 mm, 0–10.7 m, SP78-7; USNM 223063 (19) 13.0– 18.2 m, 0–1.2 m, LK 79-15; USNM 223067 (1) 13.3 mm, 0–6.1 m, SP 78-4; USNM 223068 (1) 16.3 mm, 0–0.9 m, LK 79-14. Apo Id.—USNM 223071 (2) 12.7 & 16.8 mm, 0–6.1 m, SP 78- 35; CAS 47914 (2) 16.6 & 16.8 m, 0–2.4 m, LK 79-20. Zamboanga del Norte, Allibay Id.—USNM 223066 (1) 13.6 mm, 0–3.1 m, LK 79-5. Solino (Selinog) Id.—AMS I.22206-001 (3) 13.2–15.7 mm, 13.7–21.3 m, LK 79-6; USNM 223065 (1) 12.6 mm, 12.2–18.3 m, LK 79-9. Palawan Province, Tagauayan Id.—USNM 223064 (4) 13.7–14.2 mm, 0–13.7 m, SP 78-24.

Diagnosis. The following combination of characters distinguishes E. nigramembrana from congeners: cephalic sensory-pore system pattern group I (complete); dorsal/anal fin-ray formula 8/8; 5th pelvic-fin ray absent; five internal bands between anal-fin origin and caudal-fin base; base of pectoral fin pale; a dark rectangular caudalpeduncle spot above midline; spinous dorsal fin pale, without broad dark and light bands; posterior edge of opercular membrane with a concentration of dark chromatophores; in life red-orange spots along bases of both dorsal fins, and belly with distinct red spots.

Description. Dorsal-fin rays VI-I,8 [I,8 (6), I,9 (1-OMNH P. 34238)]; anal-fin rays I,8; dorsal and anal soft rays branched except first, the last ray branched to base; pectoral-fin rays 16 (16–17, usually 16), lower rays 10–16 may be branched (usually 10–14); pelvic fins joined by membrane only at extreme base; no pelvic frenum; pelvicfin rays I,4, 4th pelvic-fin ray with 8 (6–8, usually 7 or 8) branches, 1–3 segments between branches; 5th pelvic-fin ray absent; 11 branched caudal-fin rays; segmented caudal-fin rays 17; lateral scale rows 23 (23–24); transverse scale rows 7; no scales on head, nape, breast, or pectoral-fin base; vertebrae 26; dorsal-fin spines filamentous in males and females, extending back to 3rd or 4th element of second dorsal fin; cephalic sensory-pore system compete (Group I); male genital papilla non-fimbriate, not reaching anal-fin base, sides smooth and curved with a blunt tip with a few short skin flaps on the end; mouth oblique, forming an angle of about 45° to horizontal axis of body, lower jaw not projecting; maxilla extending to center of pupil; nostrils short, not extending to upper lip and light in color; gill opening extending forward to midway between edge of preoperculum and posterior end of opercular membrane; gill membranes attached anteriorly to isthmus, without a free fold; scales on body finely ctenoid,.

Measurements (based on holotype and 6 paratypes, 11.4–14.8 mm). Head length 31.6 (30.5–34.2, 31.8); origin of first dorsal fin 36.0 (33.6–37.4, 35.7), above posterior end of pectoral-fin base; origin of second dorsal fin 56.1 (55.4–59.6, 57.2), slightly in advance of anal-fin origin; origin of anal fin 63.3 (58.5–63.3, 61.6); caudalpeduncle length 25.2 (22.9–28.5, 25.5); caudal-peduncle relatively deep, 15.8 (13.9–15.8, 15.0); body of moderate depth 23.7 (21.8–25.2, 23.6); eye diameter 10.1 (9.8–11.2, 10.4); snout length 6.1 (4.2–6.1, 5.1); upper-jaw length 10.8 (10.3–12.7, 11.2).

Color in preservative of holotype: ( Fig. 1 ). Background color of head and body pale yellowish. Head with a diffuse occipital spot about the size of the pupil (absent or faint in most paratypes), a few scattered melanophores on side of head and nape (more intense in some paratypes). Opercular membrane with an obvious concentration of melanophores contrasting with a lighter operculum and pectoral-fin base ( Fig. 2 ). Melanophores also more concentrated on membrane covering branchiostegals below operculum. Iris of eye black and pupil translucent yellow. Body without distinctive markings except for a subcutaneous rectangular dark spot above the midline over the ural centrum and five subcutaneous dark marks along the ventral surface between the anal-fin origin and caudal-fin base. Pectoral and pelvic-fin rays edged with tiny melanophores, membranes clear. Caudal-fin membranes peppered with light brown chromatophores, distal margin edged with brown. Anal fin covered with light brown chromatophores. Basal one-quarter of first and second dorsal fins heavily peppered with melanophores, remainder lightly peppered with distal margins darker.

Color of fresh holotype: ( Fig. 3 ). Background color of head translucent sky blue as is the lower half of the body. Background color of upper half of body and nape translucent cream. Head overlaid by a number of narrow irregular red-orange lines: four under the eye, the anteriormost from the anteroventral portion of the eye down across the upper lip; the second posterior to the first from the eye across the posterior part of the upper jaw; the third from under the center of the eye down posterior to the jaws continuing down under the head; the fourth extends from the posteroventral margin of the eye across the cheek onto the branchiostegal membrane. Cheek, operculum and nape also covered with narrow irregular red-orange lines. A black occipital spot present above preopercle. Scale pockets with bold red-orange pigment, the pigment on the belly scale pockets smaller, looking like spots on a white background. Five dark subcutaneous marks between anal-fin origin and caudal-fin base, each mark extending up onto the body forming lighter subcutaneous bars: the first above the first two soft rays of the anal fin; the second over rays six and seven; the next three evenly spaced along the caudal peduncle. A black rectangular spot over the ural centrum above its midpoint. Pectoral and pelvic fins sky blue. Anal fin heavily peppered with melanophores. Caudal fin with a red-orange crescent across its base, followed by a clear sky blue area. Remainder of caudal fin heavily peppered with melanophores, with larger black spots on basal half. First and second dorsal fins with red-orange spots along basal one-quarter with dense melanophores between them. Distal margins of both fins with a dark peppering of melanophores, the space in the center relatively clear. Color in life agrees with color of fresh holotype ( Fig. 4 ). One paratype (OMNH-P. 34238) has more red-orange pigmentation on the fins and body than other paratypes ( Fig. 5 ).

Distribution. Amami-oshima Island, Miyako-jima Island and Yayama Islands, the Ryukyu Islands, Japan (Akihito et al. 2002; Hayashi et al. 1990; Senou et al., 2004; in this study). Philippine Islands: Negros Oriental, Siquijor Island and Apo Island; Zamboanga del Norte, Allibay and Solino Islands; Palawan province, Tagauayan island.

Etymology. The specific epithet is an adjective combining the Latin nigra (black) and membrana (membrane), referring to the distinctive black pigment on the opercular membrane.

Comparisons. Of the 27 described species of Eviota belonging to the cephalic sensory-pore pattern group I (Greenfield & Suzuki, 2012), only three ( E. nebulosa Smith, E. nigripinna Lachner and Karnella, and E. winterbottomi Greenfield and Randall ) have the following characters shared with E. nigramembrana : a dorsal/anal formula almost always 8/8; 5th pelvic-fin ray absent or rudimentary; five or fewer dark internal spots or bands between anal-fin origin and caudal fin; no distinct markings on pectoral-fin base; and similar moderately deep body. Eviota nigramembrana has a dark internal mark above the midline of the ural centrum whereas it is on the middle of the centrum in E. nigripinna and over the entire centrum in E. winterbottomi . The spinous dorsal fin is light in E. nigramembrana whereas it is black in nigripinna and has broad dark and light bars in E. nebulosa . Eviota nigramembrana also differs from all three in live coloration: E. nigripinna has four narrow red bars across the nape that are lacking in E. nigramembrana ; E. winterbottomi has large red spots on the side of the head and six broad dark bars on the side of the body that are lacking in E. nigramembrana ; and E. nebulosa has two red bars on the cheek under the eye whereas E. nigramembrana has several narrow red bars under the eye.

Remarks. We have restricted our type material to the Ryukyu Islands, Japan because we have information on live and fresh color from there. The preserved material from the Philippine Islands agrees with preserved material from Japan in distinguishing characters, including the distinctive dark opercular membrane ( Fig. 6 ); however, we do not have information on live coloration. There are differences in the coloration of preserved specimens from the type series with the Philippine specimens having more small melanophores on the cheeks and nape and the scale pockets more heavily pigmented ( Fig. 7 ). Until future DNA studies determine otherwise, we consider the Philippine specimens to be E. nigramembrana .

Figures

FIGURE 1. Color in preservative of holotype of Eviota nigramembrana, OMNH-P. 35642. Photograph by D. W. Greenfield.

FIGURE 2. Dark pigment on opercular membrane of Eviota nigramembrana, OMNH-P. 35644. Photograph by D. W. Greenfield.

FIGURE 3. Color of fresh holotype of Eviota nigramembrana, OMNH-P. 35642. Photograph by T. Suzuki.

FIGURE 4. Underwater photograph of Eviota nigramembrana, Kasari-wan Inlet, Amami-oshima Island, the Ryukyu Islands, Japan, 6 m depth, 29 Aug. 2005, Photograph by Hiroyuki Kanehara.

FIGURE 5. Color of fresh paratype of Eviota nigramembrana, OMNH-P. 34238. Photograph by T. Suzuki.

FIGURE 6. Pigmented opercular membrane of Philippine Island specimen of Eviota nigramembrana, USNM 220062, 17.2 mm male. Photograph by D. W. Greenfield.

FIGURE 7. Eviota nigramembrana from the Philippine Islands, USNM 223063, 17.6 mm male. Photograph by K. Sandved.