Rhinogobius yonezawai, Suzuki & Oseko & Kimura & Shibukawa, 2020

Suzuki, Toshiyuki, Oseko, Naoharu, Kimura, Seishi & Shibukawa, Koichi, 2020, Rhinogobius, Bulletin of the Kanagawa Prefectural Museum (Natural Science) 49, pp. 7-28 : 15-21

Rhinogobius yonezawai sp. nov.

(New Standard Japanese name: Kemmun-hirayoshinobori)

( Figs. 7–12 ; Tables 2 & 3 )

Rhinogobius brunneus (not of Temminck & Schlegel): Nakayama, 1975: 114 (in part: Amami-oshima Island of Amami Group, the Ryukyu Islands, Japan).

Rhinogobius sp. DL: Kawanabe & Mizuno, 1989: 589 (in part: Amami-oshima Island of Amami Group, the Ryukyu Islands, Japan); Akihito et al., 1993: 1080 (in part: the Nansei Islands, Japan); Akihito et al., 2000: 1252 (in part: the Nansei Islands, Japan); Sakai et al., 2001: 117 (in part: Tanega-shima and Yaku-shima islands of Osumi Group, and Amami-oshima Island of Amami Group, the Ryukyu Islands, Japan); Akihito et al., 2002: 1252 (in part: the Nansei Islands, Japan); Yonezawa, 2002: 1 (Tanega-shima and Yaku-shima islands of Osumi Group, the Ryukyu Islands, Japan); Suzuki et al., 2004: 450 (in part: Tanega-shima and Yaku-shima islands of Osumi Group, Amami-oshima Island of Amami Group and Okinawa-jima Island of Okinawa Group, the Ryukyu Islands, Japan); Yonezawa et al., 2010: 256 (Yaku-shima Island of Osumi Group, the Ryukyu Islands, Japan); Akihito et al., 2013: 1454 (in part: Tanega-shima and Yaku-shima islands of Osumi Group, Amami-oshima Island of Amami Group and Okinawa-jima Island of Okinawa Group, the Ryukyu Islands, Japan); Motomura & Harazaki, 2017: 139 (Yaku-shima Island of Osumi Group, the Ryukyu Islands, Japan).

Holotype. OMNH-P 44049 , male, 75.2 mm SL, Issogawa River , Yaku-shima Island of Osumi Group, the Ryukyu Islands, Japan, 30°26'22.45"N 130°28'23.65"E, 16 November 2018, Fig. 7 .

Paratypes. Total 16 specimens (six males and 10 females), 45.8–71.0 mm SL, collected from Osumi Group , Amami Group and Okinawa Group , the Ryukyu Islands , Japan. Tanega-shima Island (Osumi Group): KAUM-I. 5753, 5754 (stained with Alizarin Red S), 5755, 5761, 5763, two males and three females, 49.2–64.5 mm SL O’okouda-gawa River, 30°37'34.77"N 131°2'4.02"E, 11 August 2007 . Yaku-shima Island (Osumi Group): KPM-NI 53488 and 53489 (formerly OMNH-P 44058 and 44059), male and female, 67.9 and 68.9 mm SL, stained with Alizarin Red S, Jyono-gawa River, 30°23'58.19"N 130°35'22.49"E, 9 December 2018 ; OMNH-P 44050 , female, 60.2 mm SL, collected with holotype, Fig. 8 . Amami-oshima Island (Amami Group): OMNH-P 43718 , 43720 (stained with Alizarin Red S), 43724, 43726 (stained with Alizarin Red S), two males and two females, 45.8–71.0 mm SL, Kawauchi-gawa River, 28°18'46.10"N 129°25'13.28"E, 31 May 2017 . Okinawa-jima Island (Okinawa Group): OMNH-P 43973 and 44082, male and female, 48.7 and 51.3 mm SL, stained with Alizarin Red S, Ufu-gawa River, Aha-gawa River System, 26°44′04.0″N 128°15′12.0″E, 3 October 2005 ; SPMN-PI 45463 and 45464 (formerly OMNH-P 43692 and 43693), male and female, 59.4 and 63.8 mm SL, Fun-gawa River of Aha-gawa River System , 26°43'29.27"N 128°17'12.65"E, 25 June 2015 .

Diagnosis. Rhinogobius yonezawai is distinguished from all congeneric species by the following unique combination of features: 35–39 longitudinal scales; 10+16=26 vertebrae; first dorsal fin in males high and falcate, non-filamentous, longest second and/or third spine(s) extending posteriorly to a space between bases of first and fourth second dorsal-fin branched rays when adpressed; fifth pelvic-fin segmented ray divided into four branches at its first (most proximal) segmenting point; pectoral-fin base and prepelvic areas naked; belly with small cycloid scales except for a narrow area around ventral midline or around anterior half of ventral midline; longitudinal rows of sensory-papillae on cheek with no transverse rows; a black oval spot on base of pectoral fin; two red stripes on temporal region, reaching posteriorly to, or around, dorsum of body below first dorsal fin; six to eight vertical deep-red or reddish-orange lines on caudal fin in males; a black bifurcated blotch posteriorly at base of caudal fin in females when alive or freshly collected.

Description. Dorsal-fin rays VI-I, 8* (17); anal-fin rays I, 8* (17); pectoral-fin rays 19 (3), 20* (13), or 21 (1); pelvic-fin rays I, 5* (17); segmented caudal-fin rays 8+8 (1), or 9+8* (16); branched caudal-fin rays 7+7* (11), 7+8 (1), or 8+7 (5); longitudinal scales 35 (1), 36 (1), 37* (9), 38* (5), or 39 (1); transverse scales 9 (1), 10 (5), 11* (10), or 12 (1); scales between origin of dorsal fin and dorsal insertion of pectoral fin 8 (7), 9* (4), or 10 (6); predorsal scales 2 (1), 4 (1), 6* (3), 7 (1), 8 (2), 9 (1), 11 (4), 12 (1), 13 (2), or 14(1); P-V 3/21210/9 (1), or 3/22110/9* (14); vertebrae 10+16=26* (15).

Proportional measurements based on holotype and seven paratypes ( KAUM-I 5753, 5763; OMNH-P 43718, 43724, 44050; SPMN-PI 45463, 45464,) are given in Table 2 . Body slender, slightly compressed anteriorly, compressed posteriorly. Head moderately large, slightly depressed. Snout nearly pointed and long, longer than eye diameter; snout length of males greater than that of females. Eye large, dorsolateral on head, located slightly behind a vertical through midpoint between snout tip and posterior margin of preopercle. Cheek somewhat bulbous, fleshy. Lips thick and fleshy; upper lip slightly protruding anteriorly beyond, or equal to, lower lip; gape slightly oblique; posterior margin of lower jaw not extending posteriorly to a vertical through anterior margin of eye. Anterior naris a short tube without skin flap at its tip, located slightly before the midpoint between snout tip and anterior margin of eye; posterior naris a round pore with low rim, closer to anterior naris than to eye. Gill opening extending anteriorly to a vertical through posterior margin of preopercle. Gill membranes broadly attached to isthmus. No fleshy papillae- or finger-like projections on lateral margin of shoulder girdle. Tongue free from floor of mouth, with rounded anterior margin. Genital papillae cone-shaped in males and oval in females.

Origin of first dorsal fin slightly behind a vertical through dorsal insertion of pectoral fin; first dorsal fin falcate and much higher than second dorsal fin in males, whereas in females, trapezoid, triangle or semicircular, and subequal to second dorsal fin in height; second and/or third spine(s) longest; all dorsal-fin spines slender and flexible, not filamentous; tip of longest spine (= posterior tip of the fin) extending posteriorly to a space between bases of first and fourth second dorsal-fin branched rays in males, but not extending to origin of second dorsal fin in females when adpressed. First and second dorsal fins not continued by membrane; all segmented dorsal-fin rays usually branched; usually seventh and second or third branched rays longest in males and females, respectively; posterior tip of second dorsal fin usually extending to caudal fin in males, but not reaching there in females when adpressed; posterior end of base of second dorsal fin above posterior end of anal-fin base. Origin of anal fin below a space between bases of first and third second dorsal-fin branched rays; anal fin slightly lower than second dorsal fin in height; all segmented anal-fin rays usually branched; sixth or seventh and fifth, sixth or seventh branched rays longest in males and females, respectively; posterior tip of anal fin not extending to caudal fin when adpressed. Pectoral fin oval, extending posteriorly to a vertical through a space between base of fifth spine and end of first dorsal-fin base; pectoral-fin rays branched, except dorsalmost and/or ventralmost ray(s) unbranched. Pelvic fins fused medially by well-developed frenum (between spines) and connecting membrane (between innermost rays), forming a circular cup-like disc at least in large adults; pelvic fins usually extending posteriorly to a vertical through a space between bases of second and fifth first dorsal-fin spines, and not reaching to anus; pelvic-fin spine with a rounded membranous lobe at its tip; all segmented rays of pelvic fin branched; fifth pelvic-fin segmented ray divided into four branches at its most proximal point with segment of each branch ( Fig. 9A ). Caudal fin elliptical or fan-shaped.

Scales on body largely ctenoid, becoming smaller anteriorly; a part of basal region of caudal fin, anterodorsal part of body before a diagonal line from base of sixth spine and fourth second dorsal-fin branched ray to dorsal insertion of pectoral fin, belly with small cycloid scales; scaled area of belly not extending anteriorly to pelvic-fin insertion. Predorsal squamation usually with trifurcate anterior edge; mid-anterior extension extending anteriorly to a space between transverse lines through a point slightly before origin of first dorsal fin and sensory-canal pore K'; anterior extensions of lateral sides extending anteriorly to a space between transverse lines through anterodorsal end of gill membrane and pore K' ( Fig. 9B ). The other part of head, pectoral-fin base, pelvic-fin axil and following narrow triangular area around ventral midline or around anterior half of ventral midline of belly ( Fig. 9C ), and prepelvic areas naked.

Cephalic sensory systems are illustrated in Fig. 10 . Nasal extension of anterior oculoscapular canal with terminal pore B' located above anterior naris. Anterior interorbital sections of anterior oculoscapular canal separated bilaterally, with paired pore C and a single pore D. Pore E present just behind posterior edge of eye. Lateral section of anterior oculoscapular canal with anterior pore F and terminal pore H'. Posterior oculoscapular canal with two terminal pores K' and L'. Gap between anterior and posterior oculoscapular canals much shorter than length of posterior oculoscapular canal. Preopercular canal present, with three pores M', N, and O' (a paratype without pore N). Sensory-papillae row “a” oblique and uniserial, composed of loosely-arranged papillae, extending anteriorly to a vertical through anterior margin of eye. Row “b” longitudinal, composed of densely-arranged papillae, extending anteriorly to a vertical through pupil; its length slightly longer than eye diameter. Row “c” composed of loosely-arranged papillae, extending posteriorly to a vertical through posterior margin of eye. Row “d” composed of densely-arranged papillae, extending posteriorly to a vertical through posterior margin of pupil. Row “cp” comprising a single papilla. Row “f” comprising paired papillae. Anterior end of row oi slightly separated from a vertical row “ot”.

Coloration of males when alive [ Figs. 11A, C, E, G ; Suzuki et al., 2004: 451 (middle figure)]. Ground color of head and body bluish green or yellow green. Ventral side of belly pale yellow. Cheek and lower half of operculum grayish, with many small deep-red dots, spots and/or short lines forming an irregular network pattern (indistinct in a population in Okinawa-jima Island). Snout with a broad, oblique deep-red stripe between eye and anterior one fourth of upper lip; lateral side of snout sometimes tinged with yellow. Several irregular-shaped, deep-red short stripes and botches on dorsal surface of snout, interorbital space, occipital region and nape; dorsal margin of cheek edged by a narrow deep red line and bluish green line; upper part of operculum with two oblique deep red or black stripes. Temporal region with two deep-red stripes reaching posteriorly to, or around dorsum of body below the first dorsal fin. Many of scale pockets on body with reddish orange spots. Dorsum of body with four saddle-like, large black blotches; anteriormost one at base of first dorsal fin, middle one at base of second dorsal fin, and the other two on caudal peduncle, sometimes indistinct. A longitudinal series of seven large black blotches on midlateral body; first and second ones ventral to first dorsal fin, third one ventral to between dorsal fins, fourth and fifth ones ventral to second dorsal fin, sixth one at middle of caudal peduncle, seventh one at end of caudal peduncle; all these blotches nearly rounded or rectangular, and sometimes indistinct. Membranes of vertical fins similar to body in coloration, with deep-red or reddish-orange spines/ rays; distal margins of vertical fins pale yellow. Caudal fin becoming blackened distally, with a narrow pale-yellow edge; central part of caudal fin with six vertical deep-red or reddish-orange lines. Pectoral fin greenish or yellowish, with a central part tinged with red; base of pectoral fin paler, with a distinct black oval spot. Pelvic fins bluish gray.

Coloration of female when alive ( Figs. 11B, D, F, H ; Suzuki et al., 2004: 451, lower figure). Resembles that of male, except as follows. Ground color of head, body and fins bluish gray, pale sky or pale yellow-green. In spawning season, belly bright yellow ( Fig. 11F ). Orange dots on cheek indistinct, fewer in number. Many scale pocket spots with pale spots. Stripes and blotches on head and body darker. Seventh midlateral black blotch, located at base of caudal fin, bold and bifurcated posteriorly. Caudal fin without vertical rows.

Coloration when freshly collected. Freshly-collected coloration of males ( Figs. 7 , 12A ) resembles that when alive in underwater photograph, except as follows. Ground color of head and body light or medium gray; head bluish; branchiostegal membrane pale yellow, with many small indistinct bright orange spots. Red and orange markings on head and body darker. Saddle-like black blotches on dorsum and a longitudinal series of black blotches on midlateral body hardly visible. Membranes of vertical fins grayish or reddish brown; distal margins of vertical fins white. Central part of caudal fin with usually six to eight vertical deep-red or reddish-orange lines. Pectoral and pelvic fins similar to, or slightly more darkened than, body in coloration. Freshly-collected coloration of females ( Figs. 8 , 12B ) resembles that of males, except as follows. Ground color of head and body dull yellow or grayish yellow; head and midlateral body bluish. Scale pockets with orange spots, forming a network pattern. Fin membranes light gray. Caudal fin without barred pattern. In some specimens, pectoral fin with two vertical rows of orange dots.

Coloration when preserved in alcohol. All blue, green, orange, red and yellow color faded; ground color of head and body turns to grayish brown and pale yellow in males and females respectively; blackish markings on body turn to brown.

Habitat and Distribution. Known from upper reaches of swift freshwater streams in montane areas of Tanega-shima and Yaku-shima islands of Osumi Group, Amami-oshima Island of Amami Group and Okinawa-jima Island of Okinawa Group, the Ryukyu Islands, Japan; it is an amphidromous species ( Takagi et al., 2015), although landlocked in few freshwater reservoirs of Okinawa-jima Island (present study).

Etymology. The specific name, yonezawai , refers to Mr. Toshihiko Yonezawa, who offered much information and specimens to us for our study.

Figures

Fig. 7. Holotype of Rhinogobius yonezawai (OMNH-P 44049, male, 75.2 mm SL) collected from Isso-gawa River, Yaku-shima Island, Osumi Group, Japan.A and B: freshly-collected condition; C: alcohol-preserved condition. Photographed by T. Suzuki.

Fig. 8. Female paratype of Rhinogobius yonezawai (OMNH-P 44050, 60.2 mm SL) collected with OMNH-P 44050. A and B: fresh condition; C: alcohol-preserved condition. Photographed by T. Suzuki.

Fig. 9. Ventral view of pelvic fin (A), dorsal view of head (B), and ventral view of belly (C) in Rhinogobius yonezawai (KAUM-I 5754, paratype, female, 49.2 mm SL), stained with Alizarin Red S. Annotations are as in Fig. 3. Photographed and annotated by T. Suzuki.

Fig. 10. Dorsal (top), lateral (middle), and ventral (bottom) views of head in Rhinogobius yonezawai (KAUM-I. 5755, paratype, male, 54.0 mm SL), showing cephalic sensory pores and papillae.Annotations and abbreviations are as in Fig. 4. Photographed and annotated by T. Suzuki.

Fig. 11. Underwater photographs of Rhinogobius yonezawai taking at Tanega-shima Island (A, B), Yaku-shima Island (C, D), Amami-oshima Island (E, F) and Okinawa-jima Island (G, H), Japan. A, C, E, and G: male; B, D, F, and H; female. A-F, photographed by T. Yonezawa; G and H, photographed by K. Maeda.

Fig. 12. Dorsal (top), lateral (middle), and ventral (bottom) views of head in Rhinogobius yonezawai showing freshlycollected coloration. A: OMNH-P 43718, paratype, male, 71.0 mm SL; B: OMNH-P 43724, paratype, female, 56.7 mm SL. Photographed by T. Suzuki.