Rhinogobius chongkangensis sp. nov.

(中ª吻DṀ)

(Figures. 1–4)

Materials examined

Holotype. NTOUP-2023-08-281, 36.9 mm SL, male, Aug. 20, 2023, coll., I-S. Chen, Donghe, Chongkang River basin, Maioli County, Taiwan.

Paratypes.

NTOUP-2023-08-282, 1 specimens, 31.9 mm SL, the date, collector and locality same as holotype.

NTOUP-2023-09-283, 4 specimens, 34.2–39.0 mm SL, Spt. 10, 2023, collector and locality same as holotype.

Diagnosis

Rhinogobius chongkangensis can be well distinguished from all other congeners by the unique combination of the following features: (1) fins: second dorsal fin rays I/9; anal fin rays I/8; pectoral fin rays modally 16; (2) squamation: longitudinal scale series 32–33 (modally 32); perdorsal scales 12–15 (modally 14); (4) vertebral count 27; (5) Mouth oblique, rear edge extending to vertical between anterior margin of orbit and anterior edge of pupil in male and (6) specific colouration: lateral body with 7–8 longitudinal rows of small orange to brownish red spots about 1/6–1/10 size of pupil diameter in male; cheek and opercle with 24–32 rather small orange or brownish red spots in male, with 13–16 small brown spots in female; branchiostegal membrane with many 14–18 tiny orange or brownish red spots in male; basal region of first dorsal fin with 8–12 orange or brownish red spots in male, second dorsal fin pale with 3–4 longitudinal rows of orange spots; pectoral fin with two rows of orange to red orange spots which 4–5 larger orange spots or sometimes fusing a vertical line on upper side on anterior row in male; a snow white vertical band between the two rows of orange spots in male.

Description

Body proportions in Table 1. Body cylindrical anteriorly, compressed posteriorly. Head rather large, somewhat depressed in male. Eye large, dorsolateral. Snout pointed. Cheek rather fleshy in male. Lips thick. Mouth oblique, rear edge extending to vertical between anterior margin of orbit and anterior edge of pupil in male, but not extending beyond vertical anterior margin of orbit in female. Both jaws with 3–4 rows of conical teeth, outer jaws enlarged. Tongue margin rounded. Anterior nostril in short tube and posterior nostril round. Gill opening small, extending ventrally to vertical of rear margin of cheek. Vertebral count 10 + 17 = 27 (examined in 6 specimens).

Fins. D1 VI, D2 I/9–10 (modally I/9); AI/8; P 15–16 (modally 16); V I/5+I/5. D1 rounded, 3rd and 4th rays slightly longer, with rear tip while depressed not extending to or just reaching vertical of D2 origin in male.

Origin of A inserted below or slightly behind second branched rays of D2. Rear tips of D2 and A fin rays not extending to procurrent rays of C in male. P moderate large and oblong, rear tip not reaching vertical line through anus in male. V small and rounded, spinous rays with somewhat pointed membrane lobe. C elliptical, rear edge rounded.

Scales. Body with moderately large ctenoid scales, anterior region of predorsal area naked; posterior dorsal area and belly cycloid. LR 32–33 (modally 32); TR 10–11 (modally 11); PreD 12–15 (modally 14); and SDP 8–9 (modally 9) (distribution frequency in Table 2). Head and prepelvic region naked. Anterior edge of midpredorsal squamation extending beyond the vertical of midline of opercle.

Head lateral-line system. (Figure 1)

Canals: Nasal extension of anterior oculoscapular canal with terminal pore σ located in between anterior and posterior nostrils. Anterior interorbital sections of oculoscapular canal with paired pore λ. A single pore κ in near rear of interorbital region in lacking both with paired pore λ and pore ω. Lateral section of anterior oculoscapular canal with terminal pore α. No posterior oculoscapular canal. No preopercular canal.

Sensory papillae: Row a extending beyond vertical midline of orbit. Row b length about equal to eye diameter. Rows c, d longer. A single cp papilla. Row f paired. Anterior edge of row oi near lower region of row ot.

Colouration while fresh. (Figures 2–4)

Body creamy yellow to yellowish brown. Side of body without distinct gray or brown blotches or merely with very faint smaller gray blotches in middle lateral side; lateral body with 7–8 longitudinal rows of small orange to brownish red spots about 1/6–1/10 size of pupil diameter in male; orange brown spots less than 1/4 of pupil diameter in female. Dorsal region of body with about 6 indistinct gray blotches.

Head creamy yellow to yellowish brown. Cheek and opercle with 24–32 rather small orange or brownish red spots in male, with 13–16 small brown spots in female. Nape with many orange or brown spots. Snout on dorsal side with a pair of red to brown stripe united at snout tip. Snout on lateral side with two parallel brownish gray stripes (orange one as posterior stripes in male) both terminating toward margin of upper jaw; lower one brownish red but lacking any narrow blue margin in male, but brownish gray in female. Lips and dorsal snout pale brown. Branchiostegal membrane with many 14–18 tiny orange or brownish red spots in male, but rather few spots or spotless in female. Isthmus creamy yellow.

First dorsal fin pale brown with broad orange pink band on distally 1/3 or 1/2 area. A middle grayish black spot in front of third spine of first dorsal fin in both sexes. The spot usually smaller in female. Basal region of first dorsal fin with 8–12 orange or brownish red spots in male, 6–8 brown spots in female. Second dorsal fin pale with orange pink band on distal 1/3–1/4 region, 3–4 longitudinal rows of orange spots in both sexes. Anal fin orange basally with distal gray margin. Caudal fin surrounding with distally grayish brown zone in male accompanying with 4–7 somewhat vertical rows of orange or brownish red spots; with pale brown zone in female accompanying with 3–4 vertical rows of small brown spots. Pectoral fin with two rows of orange to red orange spots which 4–5 larger orange spots or sometimes fusing a vertical line on upper side on anterior row in male; with two rows (anterior 3–4 larger ones; posterior 3–4 smaller ones) of brown spots in female. A snow white vertical band between the two rows of orange spots in male near the basal region of pectoral fin; pale white in female. Pelvic fin pale gray in male, whitish in female.

Etymology

The specific name— chongkangensis is referred to the type locality: “Chongkang River basin” of Western Taiwan.

Distribtuion

The new species could be endemic and only found in the several hill-streams of Chong-Kong River basin, Miaoli County, Taiwan.

Remarks

The new species can be immediately separated from all nominal congeners from Taiwan including typical longitudinal infraorbital sensory papillae group - Rhinogobius candidianus (Regan, 1908), Rhinogobius formosanus Oshima, 1919, Rhinogobius gigas Aonuma & Chen, 1996, Rhinogobius nantaienesis Aonuma & Chen, 1996, Rhinogobius delicatus Chen & Shao, 1996, Rhinogobius maculafascistus Chen & Shao, 1996, and Rhinogobius lanyuensis Chen, Miller & Fang, 1998 by high vertebral account modally 27 vs. 26 and lower count of pectoral fin rays modally 15–16 vs. more than 17.

Within the species group with higher vertebral count as 27, this new species is more similar to Rhinogobius yangminshanensis rather than Rhinogobius rubromaculatus group (also included both Rhinogobius baborinisanensis Chen & Yeh, 2024; Rhinogobius macromaculatus Chen & Yeh, 2024) than any other congeneric species with same dorsal fin formula as I/9 from Taiwan.

However, Rhinogobius chongnkangensis sp. nov. eventually can be well distinguished from Rhinogobius yangminshanensis Chen et al., 2022a by the following features: (1) longitudinal scales: longitudinal scale rows usually 32–33 vs. longitudinal scale 30–31; (2) predorsal scales: modally 14 vs. 12; (3) cheek spots: always representing smaller orange spots ones of cheek around 1/6–1/10 size of pupil diameter in male vs. about equal to 1/3 of pupil diameter in male; (4) smaller size of mouth: rear edge of mouth extending to midline of anterior margin of orbit and anterior edge of pupil in male vs. rear edge of mouth extending to vertical of anterior margin of pupil in male; (5) more spotty in first dorsal fins: usually 7–10 reddish brown to deep brown spots in basal first dorsal fin membrane in male vs. 3–4 larger spots in male; and (6) pectoral fin vertical stripe: usually in having distinct snow white bar in male vs. somewhat bluish in male.

Our unpublished research data of mtDNA D-loop sequences has also revealed that great mitogenetic differentiation between them, the detailed molecular phylogenetic relationship with more recently described data would be reconstructed in coming working paper (Chen, unpublished data).