Rhinogobius estrellae Maeda, Kunishima & Palla, 2021

Maeda, Ken, Shinzato, Chuya, Koyanagi, Ryo, Kunishima, Taiga, Kobayashi, Hirozumi, Satoh, Noriyuki & Palla, Herminie P., 2021, Two new species of Rhinogobius (Gobiiformes: Oxudercidae) from Palawan, Philippines, with their phylogenetic placement, Zootaxa 5068 (1), pp. 81-98 : 84-89

Rhinogobius estrellae Maeda, Kunishima & Palla , new species

[New English name: Estrella goby]

( Figs. 1–5 ; Tables 2–6 )

Material examined. Eight males and 16 females from Narra , Palawan Island in the Philippines .

Holotype. NSMT-P 140091 , male (40.6 mm SL), Estrella Falls , 13 May 2016, coll. K. Maeda, T. Kunishima, and H. P. Palla.

Paratypes. NSMT-P 140092 , female (38.9 mm SL), same data as holotype; URM-P 49295–49301, 1 male (40.7 mm SL) and 6 females (36.1–40.9 mm SL), same data as holotype; URM-P 49302, female (43.0 mm SL), creek in front of the Estrella Village Barangay Hall , 28 May 2018, coll. K. Maeda, H. Kobayashi, and H. P. Palla ; URM-P 49303–48306, 2 males (37.8–39.6 mm SL) and 2 females (36.4–45.3 mm SL), Estrella Falls , 28 May 2018, coll. K. Maeda, H. Kobayashi, and H. P. Palla ; WPU-PPC-P 50–54, 1 male (37.5 mm SL) and 4 females (35.5–41.1 mm SL), same data as holotype; WPU-PPC-P 55–59, 3 males (37.3–38.4 mm SL) and 2 females (33.2–37.8 mm SL), Estrella Falls , 28 May 2018, coll. K. Maeda, H. Kobayashi, and H. P. Palla.

Diagnosis. Pectoral fin with 14–16 rays (usually 15 rays). Nape and posterior part of occipital region covered by cycloid scales; scaled area extending anteriorly to around a vertical line through posterior margin of preopercle or a little posterior to this line. Longitudinal scales 27–31, predorsal scales 3–11. Number of vertebrae 26. Cephalic sensory pore system usually with B´, C, D(S), E, F, H´, K´, L´, M´, N, and O´, but often lacking one or both side(s) of pore E. Transverse rows of sensory papillae on cheek. In preservative, lateral and dorsal sides of body with dark brown mesh-like markings, snout and cheek with three dark brown stripes, and pectoral fin with dark brown band vertically across proximal part of the upper and middle rays except lower 2–6 rays. In life, upper and middle parts of pectoral-fin base with bright white vertical band.

Description. Body nearly cylindrical anteriorly and somewhat compressed posteriorly. Head depressed and larger in male than female (head length 33.5–36.0 vs 30.3–32.9% of SL; Fig. 3 ). Eyes located dorsolaterally. Mouth terminal and oblique with thick upper and lower lips. Anterior tips of upper and lower jaws almost even or upper jaw slightly protruding beyond lower jaw. Posterior end of upper jaw always exceeding a vertical line through anterior margin of eye. Mouth larger in male than female (upper-jaw length 14.1–16.1 vs 10.5–11.9% of SL; Fig. 3 ). Anterior nostril short tubular, posterior nostril a pore. Cephalic sensory pore system usually with B´, C, D(S), E, F, H´, K´, and L´ in oculoscapular canal and M´, N, and O´ in preopercular canal, but 5/ 24 specimens lacking one pore C, 2/ 24 specimens lacking both pores C, 7/ 24 specimens lacking one pore E, 5/ 24 specimens lacking both pores E, 3/ 24 specimens having pore G on one side, and 1/ 24 specimens lacking one pore N. One specimen having an additional single pore anterior to another single pore D. Arrangement of cutaneous sensory papillae of head shown in Fig. 4 . Cheek having two longitudinal rows of papillae and 4–6 transverse rows both between eye and upper longitudinal row and between upper and lower longitudinal rows. Vertebrae 10+16=26 (n=9) or 11+15=26 (n=1), P-V 3/II II I I 0/9 (n=9) or 3/II I II II 0/9 (n=1).

First dorsal fin usually with six spines supported by six pterygiophores, but 1/ 24 specimen with seven spines supported by seven pterygiophores. Second dorsal fin usually with one spine and eight soft rays, but 3/ 24 specimens with one spine and seven soft rays. First- and second-dorsal-fin bases separated each other by a small interval (0.3–3.9% of SL). First dorsal fin rounded, usually almost semi-circular; posterior tips of fin (usually tips of fourth to sixth spines) not reaching second dorsal fin origin (n=13), just touching base of second-dorsal-fin spine (n=6), or exceeding base of second-dorsal-fin spine but not reaching base of first soft ray of second dorsal fin (n=5). Anal fin usually with one spine and eight soft rays, but 3/ 24 specimens with one spine and seven soft rays and 2/ 24 specimens with one spine and nine soft rays. Caudal fin with 17 segmented rays, including 12 (n=3), 13 (n=9), or 14 (n=12) branched rays; posterior margin rounded. Male having larger second dorsal, anal, and caudal fins than female (second-dorsal-fin length 34.6–38.7 vs 27.7–30.2% of SL, anal-fin length 31.3–33.7 vs 24.2–29.3% of SL, and caudal-fin length 28.6–31.7 vs 24.4–28.0% of SL; Fig. 3 ). Pectoral fin with 14–16 rays (usually 15 rays) ( Table 2 ). Pelvic fin with one spine and five soft rays; pelvic fins joined together to form a cuplike disk with fleshy bilobed frenum. Posterior tip of pelvic fin located below middle of first-dorsal-fin base.

Ctenoid scales covering lateral side of body and dorsal and ventral sides of caudal peduncle. Nape and posterior part of occipital region covered by cycloid scales; scaled area extending anteriorly around vertical line through posterior margin of preopercle (above pore H´) or to a little posterior to this line (above area between pores H´ and K´). Other regions in head naked. Belly and first-dorsal-fin base covered with cycloid scales. A few cycloid scales also occurring on trunk behind pectoral fin, along bases of second dorsal, anal, and caudal fins, and on proximal part of caudal fin. Pectoral-fin base and breast (prepelvic area) probably naked (at least invisible without staining by arizarin red; see Suzuki et al., 2016). Longitudinal scales 27–31 (usually 28–30), transverse scales 8–10 (usually 9), transverse scales in caudal peduncle always 7, and predorsal scales 3–11 ( Tables 3–5).

Colour in preservative ( Fig. 1 ): Background of head and body cream. Head with three dark brown stripes; upper one running on snout and connecting upper lip and eye; lower two running diagonally across cheek and connecting upper lip and posterior margin of preopercle. These stripes often broken-up with gaps, branches, and additional dots. Posterior margin of opercle fringed by narrow dark brown vertical band. Pectoral-fin base dark brown with thin, whitish vertical line along bases of middle and ventral rays. Scales on dorsal and lateral sides of body having dark brown margins forming mesh-like patterns. Darkness of scale margins variable and body often showing four or five dark brown saddles from trunk to caudal peduncle. First and second dorsal fins greyish brown with multiple transparent or pale grey spots on proximal and middle parts. Anal fin pale grey or greyish brown, often darker in males. Caudal fin pale grey or greyish brown with 6–10 dark brown vertical bands, but ventral part lacking these bands. Pectoral fin pale grey or greyish brown with a dark brown vertical band proximally on upper and middle parts. Pelvic fin pale grey or greyish brown.

Colour in life ( Fig. 5 ): Background of head and body pale reddish- or yellowish grey but more whitish on ventral side; ventral surface of head and belly often tinged with orange. Dark brown markings on head and body described in “colour in preservative” present but more reddish. Background of cheek and opercular region often tinged with greyish blue. Pectoral-fin base black with a bright white vertical band posteriorly on upper to middle parts, and often tinged with greyish blue anteriorly. Background of body tinged with sky blue. First and second dorsal fins reddish brown or orange with many white spots on proximal and middle parts. Anal fin reddish brown or orange but proximal and posterior parts greyish blue. Caudal fin reddish brown or orange with 6–10 translucent or white transverse bands on middle part. Pectoral fin translucent often lightly tinged with orange, and proximal parts of some ventral rays white. Pelvic fin pale orange proximally and light grey or greyish blue distally.

Distribution. Rhinogobius estrellae is endemic to Palawan Island, Philippines. Most of the specimens examined were collected from a pool and the lower reaches of a stream below the Estrella Falls (9°21'26"N 118°23'50"E), located where a steep stream from Mt. Victoria (1,726 m) comes out to a large plain in Narra, Sulu Sea-side of the island. This new species was abundant in the pool below the first major fall with many cyprinids and gobies but absent in the reaches above it which are occupied by sicydiine gobies including Sicyopus zosterophorus (Bleeker) and Lentipes palawanirufus Maeda & Palla , and eels of the genus Anguilla Schrank (unidentified to species level). The new species was also found in a creek in front of the Barangay Hall of Estrella Village (9°21'28"N 118°24'58"E), drawing from the stream below Estrella Falls. The stream flows into Malatgao River. When we surveyed a site in the middle reaches of the Malatgao River (9°20'16.7"N 118°27'27.0"E), no Rhinogobius were found there. The water at Estrella Falls was cool even during the hottest dry season (May) in this region (water temperature was 26.5°C when measured on 13 May, 2016), while water in the Malatgao River was warmer (appeared to be nearly 30°C although we did not measure).

Etymology. The type locality of the new species is Estrella Falls in Barangay Estrella Village. Therefore, the new species is named as Rhinogobius estrellae , derived from Estrella, and the Latin suffix -e.

Figures

FIGURE 1. Preserved specimens of Rhinogobius estrellae (a–d, paratypes) and Rhinogobius tandikan (e–h, paratypes). Specimens in the left side are males, the right side are females. a, URM-P 49305, 39.6 mm SL; b, WPU-PPC-P 55, 38.4 mm SL; c, URM-P 49296, 36.1 mm SL; d, URM-P 49306, 36.4 mm SL; e, URM-P 49314, 46.9 mm SL; f, URM-P 49315, 46.5 mm SL; g, URM-P 49318, 45.2 mm SL; h, URM-P 49320, 37.9 mm SL (photo by K. Maeda).

FIGURE 2. Rhinogobius estrellae. immediately after fixation. a, NSMT-P 140091, holotype, male, 40.6 mm SL; b, URM-P 49297, paratype, female, 37.5 mm SL (photo by K. Maeda).

FIGURE 3. Head length, upper-jaw length, second dorsal-fin length, anal-fin length, and caudal-fin length of Rhinogobius estrellae (red circles) and Rhinogobius tandikan (blue triangles). Solid and open symbols represent males and females, respectively.

FIGURE 4. Arrangement of cephalic sensory pores and cutaneous sensory papillae in Rhinogobius estrellae (NSMT-P 140091, holotype). a, lateral view; b, dorsal view; c, ventral view. AN, anterior naris; PN, posterior naris.

FIGURE 5. In situ underwater photographs of Rhinogobius estrellae in Estrella Falls, Palawan. a, male, 28 May 2018; b, male, 13 May 2016; c and d, females, 13 May 2016 (photo by K. Maeda).