Rhinogobius macromaculatus, Chen & Yeh, 2024

Chen, I-Shiung & Yeh, Ming-Fon, 2024, Two new freshwater gobiid species of Rhinogobius Gill, 1859 (Teleostei: Gobiidae) from Taiwan, Zootaxa 5550 (1), pp. 333-353 : 344-348

Rhinogobius macromaculatus n. sp.

(大Ễ吻Ṟğ)

( Figs. 6–10 )

Materials examined

Holotype.—NTOUP-2024-09-520, 35.0 mm SL, coll. I-S. Chen, Spt. 10, 2024, small tributary of Tzeng-Wen River basin, Tainan County, Taiwan, ROC.

Paratypes.

NTOUP-2024-09-521, 2 specimens, 32.3–33.8 mm SL, coll. Date and locality data same as above holotype.

NTOUP-2024-09-522, 2 specimens, 31.0– 31.5 mm SL, coll. Date and locality data same as above holotype.

Diagnosis

Rhinogobius macromaculatus n. sp. which collected from southern Taiwan can be well distinguished from all other congeners by the unique combination of the following features: (1) fins: second dorsal fin rays modally I/8; anal fin rays I/7; pectoral fin rays modally 15; (2) squamation: longitudinal scale series 27–28 (modally 28); perdorsal scales usually 14–15; scales between first dorsal fin origin to upper pectoral fin base modally 8 (3) vertebral count 27; (4) rear edge of mouth: merely extending to vertical of anterior margin of pupil in male and (5) specific colouration: lateral body with 7–8 longitudinal rows of bright orange to orange red spots about 1/2 to 1/3 of pupil diameter in male; orange brown spots less than 1/3 of pupil diameter in female. Cheek and opercle with moderately large 32–36 orange spots in male, with small brown spots 12–16 in female. Larger cheek spot about 1/5 of pupil diameter. Branchostegal membrane with 20–24 small reddish orange spots on either side in male, but spotless in female. A large, middle black spot in front of third spine of first dorsal fin. The height of black spot is 1/2 of second spine. Basal region of first dorsal fin with 7–8 orange or brownish orange spots in male. Second dorsal fin with 2–3 longitudinal rows of orange spots in male. Pectoral fin with two rows usually 3+4 (totally 7–8 spots) of orange to reddish orange spots in male.

Description

Body proportions in Table 1 . Body rather robust, 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 or just beyond vertical of anterior margin of eye in male, but not reaching vertical 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 and restricted, extending ventrally to vertical midline of opercle. Vertebral count 10 + 17 = 27 (examined in all 5 specimens).

Fins.—D1 VI, D2 I/8; A I/7; P 14–15 (modally 15); V I/5+I/5 (distribution frequency in Table 2 ). D1 rounded, 3 rd and 4 th rays slightly longer, with rear tip while depressed extending to D2 origin in male. Origin of A inserted below second branched rays of D2. Rear tips of D2 and A fin rays extending near or beyond procurrent rays of C in male. P moderate large and oblong, rear tip near but 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 28–29 (modally 28); TR 9; PreD 14–15 (modally 14); and SDP 8–9 (modally 8) (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 7 )

Canals: Nasal extension of anterior oculoscapular canal with terminal pore σ located in between anterior and posterior nostrils. 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 rather long, extending forward beyond vertical of anterior margin 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 well separated to lower region of row ot.

Colouration while fresh.— ( Figures 6 , 8–10 ).

Body creamy yellow to yellowish brown. Side of body without distinct gray or brown blotches or merely with very faint gray blotches; lateral body with 7–8 longitudinal rows of bright orange to orange red spots about 1/2 to 1/3 of pupil diameter in male; orange brown spots less than 1/3 of pupil diameter in female. Dorsal region of body with 5–6 indistinct gray blotches.

Head creamy yellow to yellowish brown. Cheek and opercle with moderately large 32–36 orange spots in male, with small brown spots 12–16 in female. Larger cheek spot about 1/5 of pupil diameter in male. Nape with many orange spots in male, with small brown spots in female. Snout on dorsal side with a pair of red to brown stripe united at snout tip. Snout on lateral side with an infraorbital brownish orange stripe. Lips and dorsal snout pale brown. Branchiostegal membrane with 20-24 small reddish orange spots on either side in male, but spotless in female.

First dorsal fin pale brown with light yellow band on distally 1/3–1/4 area in front of third spine. A large, middle black spot in front of third spine of first dorsal fin; an additional small spot on third spine in female. The height of anterior black spot is about 1/2 of second spine. Basal region of first dorsal fin with 7–8 orange or brownish orange spots in male, 4–5 brown spots in female. Second dorsal fin pale gray with 2–3 longitudinal rows of orange spots in male; translucent with thin gray band, 3–4 longitudinal blackish brown spots in female. Second dorsal fin with narrow snow white margin in both sexes. Anal fin light orange to pinkish orange with distal gray band and outer narrow white margin. Caudal fin surrounding with distally grayish black zone in male accompanying with 3–4 vertical rows of bright orange spots; with pale brown zone in female accompanying with 3–4 vertical rows of small brown spots. Caudal fin membrane with narrow snow white margin in both sexes. Pectoral fin with two rows usually 3+4 (totally 7–8 spots) of orange to reddish orange spots in male; with two rows (totally 5–6 spots) of smaller brown spots in female.A pale white band between the two rows of orange spots in male near the basal region on dorsal half of pectoral fin. Pelvic fin pale gray in male, whitish in female.

Etyomology

The specific name “ macromaculatus ” is referred to the specific feature of “large spot” as bluish black pigmentation on dorsal fin (latin macro + maculate) of the current species.

Distribution

The new species is endemic species in fresh waters of Taiwan. So far, it is found from the small tributaries of Tzeng-Wen River basin, southern Taiwan.

Remarks

The new species, Rhinogobius macromaculatus is rather similar to Rhinogobius rubromaculatus Lee & Chang, 1996 than any other congeneric species. However, they can be well distinguished from Rhinogobius rubromaculatus by the following features: (1) pectoral fin rays: modally 15 vs. 16; (2) predorsal scales usually 14 vs. 11; (3) scales between first dorsal fin origin to pectoral fin base modally 10 vs. 8; (4) longitudinal scales: larger scales as modally 28 vs. modally 29; and (5) specific coloration: blotches of first dorsal fin: larger, wide black blotch in front of the third rays and the height of dorsal fin blotch about 1/2 length of second dorsal ray in male vs. smaller bluish black blotch in front of third dorsal fin ray and the height of dorsal fin blotch less than 1/3 length of second dorsal fin ray in male; pectoral fin base: in having 3–4 orange spots in second row in male vs. 7–8 orange spots in second row in male.

Furthermore, the unpublished mitogenetic data of current new species, Rhinogobius macromaculatus has revealed that it has also shown the distinct divergence of mtDNA sequences from the discrete species, Rhinogobius rubromacultatus Lee & Chang, 1996 (Chen et al. unpublished). The full picture for resolving taxonomic puzzle of some river basins for such as Rhinogobius rubromaculatus complex is still needed. The detailed molecular phylogenetic relationship with all nominal Rhinogobius species from Taiwan would be surveyed and discussed in near future.

Figures

FIGURE 6. Rhinogobius macromaculatus n. sp., A. holotype, 35.0 mm SL, B. paratype, 32.3 mm SL, Tzeng-Wen River basin, Tainan County, Taiwan.

FIGURE 7. Head lateral-line system of Rhinogobius macromaculatus n. sp., holotype, 35.0 mm SL, Tzeng-Wen River basin, Tainan County, Taiwan. (Bar = 1 mm).

FIGURE 8. Head pigmentation pattern of Rhinogobius macromaculatus n. sp., holotype, 35.0 mm SL, Tzeng-Wen River basin, Tainan County, Taiwan.

FIGURE 9. Pigmentation pattern of first dorsal fin of Rhinogobius macromaculatus n. sp., holotype, 35.0 mm SL, Tzeng-Wen River basin, Tainan County, Taiwan.

FIGURE 10. Ventral view of head of Rhinogobius macromaculatus n. sp., holotype, 35.0 mm SL, Tzeng-Wen River basin, Tainan County, Taiwan.