Rhinogobius nami Maeda, Kobayashi, Iida & Tran, 2024, sp. nov.

Rhinogobius nami, sp. nov. (Figs. 2, 3d–f, 6c, d, 7, 8; Tables 1–7) Holotype. NSMT-P 147890, male (24.9 mm SL), Suoi Mo, a tributary of Song Han, Hoa Vang District, Da Nang City (16°00’01.3”N 108°03’33.2”E), 17 June 2019. Paratypes. HNUE-F 351–352, 1 male (27.2) and 1 female (24.8 mm SL), Suoi Mo, a tributary of Song Han, Hoa Vang District (15°59’58.1”N 108°04’12.7”E), 27 January 2018; HNUE-F 353–354, 1 male (25.1) and 1 female (28.7 mm SL), same data as holotype; NSMT-P 147889, female (32.4 mm SL), same data as holotype; OISTICH 272–273, 1 male (26.9 mm SL) and 1 female (27.5 mm SL), Suoi Mo, a tributary of Song Han, Hoa Vang District (15°59’57.7”N 108°04’10.0”E), 1 March 2016; OISTICH 274–275, 1 male (27.5 mm SL) and 1 female (30.6 mm SL), Suoi Hoa, a tributary of Song Han, Hoa Vang District (15°57’20.2”N 107°58’16.4”E), 2 March 2016; OISTICH 276–278, 3 females (28.0– 29.3 mm SL), Suoi Mo, a tributary of Song Han, Hoa Vang District (15°59’58.1”N 108°04’12.7”E), 27 January 2018; OISTICH 279, female (26.8 mm SL), Suoi Hoa, a tributary of Song Han, Hoa Vang District (15°57’20.2”N 107°58’16.4”E), 27 January 2018; OISTICH 280–290, 3 males (25.3–28.3 mm SL) and 8 females (27.0– 30.6 mm SL), same data as holotype. Diagnosis. Pectoral fin with 14–16 rays. Second dorsal and anal fins usually with one spine and eight soft rays. Number of vertebrae usually 26. Nape and posterior part of occipital region covered by cycloid scales; scaled area extending anteriorly to about halfway between posterior margins of preopercle and opercle. Longitudinal scales 28–31, transverse scales eight or nine, and predorsal scales 6–11. Cephalic sensory pore system usually with B´, C, D(S), E, F, H´, K´, L´, M´, N, and O´. Five, longitudinal, reddish-brown or dusky-brown stripes (dotted lines) running from trunk to caudal peduncle both in male and female; fourth (from dorsal) one slightly below lateral midline most distinct and others sometimes unclear. Male having three parallel, diagonally downward, reddish-brown or dusky-brown stripes on ventral part of cheek. Opercular membrane, interopercle, and lower part of subopercle of live male specimen light bluish-grey with many red or orange spots. Description. Body nearly cylindrical anteriorly and somewhat compressed posteriorly. Anterior tip of head pointed in female but rounded in male. Head larger in male than female (head length 31.3–34.5 vs. 28.4–30.9% of SL; Fig. 2, Table 3). Eyes located dorsolaterally. Mouth terminal and oblique with thick upper and lower lips. When mouth closed, anterior tips of upper and lower jaws almost even or lower jaw protruding slightly beyond upper jaw. Upper jaw extending posteriorly to center of eye in male, but ending below anterior part of eye (between anterior margin of eye and anterior margin of pupil) in female. Mouth larger in male than female (upper-jaw length 11.6– 13.8 vs. 8.4–9.6% of SL; Fig. 2, Table 3). Upper and lower jaws usually with 2–4 rows of conical teeth; those in outermost row enlarged and those in inner rows irregularly aligned. Mental flap on chin usually round or rectangular, often with a small central projection. Anterior nostril short tubular, posterior nostril a pore. Cephalic sensory pore system with B´, C, D(S), E, F, H´, K´, and L´ in oculoscapular canal and M´, N, and O´ in preopercular canal of both left and right sides in 20 of 25 specimens examined (including holotype; Fig. 3d–f), but three specimens having pore G in one or both side(s), and two specimens having an additional pore behind pore F (not G, but near F) in one or both side(s). Arrangement of cutaneous sensory papillae of head shown in Fig. 3d–f. Cheek having no significant transverse row of papillae. Vertebrae 10+15=25 (n=1) or 10+16=26 (n=13; Table 1), P-V 3/II II I I 0/9 (n=14). First dorsal fin usually with six spines, but one specimen with five. Second dorsal fin usually with one spine and eight soft rays, but three specimens with one spine and seven soft rays (Table 2). First and second dorsal-fin bases separated by a small interval (2.8–5.8% of SL; Table 3). In female, first dorsal fin rounded, almost semi-circular; posterior tip of fin (tips of fourth to sixth spines) not reaching second dorsal-fin origin. In male, first dorsal fin in parallelogram shape; posterior tip of fin (usually fourth spine) extending to, or exceeding base of second dorsal-fin spine, but never reaching base of second soft ray of second dorsal fin. Anal fin with one spine and seven (n=4) or eight (n=21) soft rays (Table 2). Caudal fin with 17 segmented rays including 12 (n=15), 13 (n=9), or 14 (n=1) branched rays; posterior margin rounded. Male having larger second dorsal, anal, and caudal fins than female (second dorsal-fin length 31.2–37.5 vs. 25.0–28.3% of SL, anal-fin length 27.6–30.1 vs. 23.5–27.2% of SL, and caudal-fin length 26.5–29.6 vs. 21.8–26.6% of SL; Fig. 2, Table 3). Pectoral fin with 14–16 rays (mode 15 rays) (Table 4). Pelvic fin with one spine and five soft rays; pelvic fins joined together to form a cuplike disc with fleshy bilobed frenum. Ctenoid scales covering lateral, dorsal, and ventral surfaces of body posterior to flank except belly. Nape and posterior part of occipital region covered by cycloid scales; scaled area extending anteriorly around middle between posterior margin of preopercle and posterior margin of opercle both in male and female. Other regions of head naked. Belly and flank covered with cycloid scales. First and second dorsal, and anal-fin bases covered with ctenoid scales and a few small cycloid scales mixed. Proximal part of caudal fin covered with cycloid scales. Scales on breast (pre-pelvic area) difficult to detect, but cycloid scales observed in a few individuals. Pectoral-fin base probably naked (at least invisible without staining with alizarin red; see Suzuki et al. 2016). Longitudinal scales 28–31, transverse scales eight or nine, transverse scales in caudal peduncle seven, and predorsal scales 6–11 (Tables 5–7). Color in life and fresh (Figs. 7 and 8): in male, background of head and body cream or yellowish-brown, but whitish on ventral side. A clear, reddish-brown stripe across center of upper lip; stripe splitting to left and right sides at snout and extending to anterior margin of eyes and continuing posteriorly from posterior margin of eye to region above gill opening, but posterior half indistinct. Dorsal side of head above this stripe, grey or brown. Lower half of cheek and opercular region darker than upper half, sometimes strongly contrasting. Reddish-brown or dusky-brown spot at posterior part of upper lip. Three parallel, diagonally downward, reddish-brown or dusky-brown stripes on ventral part of cheek. Opercular membrane, interopercle, and lower part of subopercle light bluish-grey with many red or orange spots. Posterior part of lower lip also often light bluish-grey. Five longitudinal, reddish-brown or dusky-brown stripes (formed by dotted lines) running on lateral and dorsal sides from trunk to caudal peduncle; fourth one (counted from dorsal) slightly below lateral midline being most distinct and others sometimes unclear. Three to six indefinite dusky transverse bands sometimes appearing on lateral side of body. First dorsal fin with series of black or dusky-brown markings on middle parts of membranes between first to fifth spines; marking between first and second spines largest and clearest, and posterior ones sometimes unclear. Distal part of membrane light blue or white between first and second spines, and orange or red between second and fifth spines. Distal part of spines black or grey. Reddish-brown spots on proximal part of first to fourth spines; spines and membranes white between proximal reddish-brown spots and middle black or dusky-brown markings. Two or three indefinite reddish-brown stripes on membranes posterior to fifth spine and white between stripes (in most specimens, as in Fig. 8a, but stripes sometimes disordered, as in Fig. 7a). Second dorsal fin with three to six reddish-brown spots aligned along each spine and soft rays; membrane around these spots also reddish-brown and forming stripes across fin. Proximal and middle parts of spine, soft rays, and membranes white between reddish-brown spots. Distal margin of second dorsal fin white or light blue. Black, vertical rectangular or elliptical spot surrounded by cream and orange at middle of proximal part of caudal fin. Remainder of caudal fin white or translucent with many reddish-brown spots forming five to eight vertical bands, but ventral part orange or dark brown. Anal fin orange, but dusky brown distally with bluish-white margin. Pectoral fin greyish translucent or grey, but its proximal part light yellowish-brown or light grey with large black or reddish-brown blotch at middle of pectoral-fin base. Pelvic disc greyish translucent or dark grey with white or light blue margin. In female, markings and background color of head and body similar to those of male, but lacking three parallel, diagonally downward stripes from ventral part of cheek. Opercular membrane, interopercle, lower part of subopercle, and posterior part of lower lip yellowish-brown or dark grey without red spots. First dorsal fin translucent with one to five indefinite reddish-brown spots along each spine; proximal parts of spines white between reddish-brown spots; distal part of fin yellow. Markings and background of second dorsal, caudal, and pectoral fins similar to those of male, but white margin of second dorsal fin thinner and often indistinct, and ventral part of caudal fin translucent instead of orange. Anal fin translucent, but reddish or dark brown distally with thin, bluish-white margin. Pelvic disc translucent with white margin. Color in preservative (Fig. 6c, d): background of head and body cream and that of fins translucent or light brown. Reddish-brown markings observed in life becoming dark-brown, and dusky-brown markings becoming