Opsariichthys iridescens Peng, Zhou & Yang, 2024

Peng, Xin, Zhou, Jia-Jun, Gao, Hong-Di & Yang, Jin-Quan, 2024, A new species of Opsariichthys (Teleostei, Cypriniformes, Xenocyprididae) from Southeast China, ZooKeys 1214, pp. 15-34 : 15-34

Opsariichthys iridescens Peng, Zhou & Yang sp. nov.

Figs 2 , 3 A, B

Type material.

Holotype • SHOU 202210001 , male, adult, 91.0 mm standard length (SL), collected by Jia-Jun Zhou and Hui Cao in October 2022, in Lin’an District, Hangzhou City, Zhejiang Province ( Qiantang River ) (30.2368 ° N, 119.7196 ° E) . Paratypes • SHOU 202210002 – SHOU 202210010 , 9 specimens, 79.1–96.0 mm standard length (SL), collected by Jia-Jun Zhou and Hui Cao in October 2022, from the same locality as the holotype ; SHOU 202106089 , SHOU 202106090 , and SHOU 202106125 , 3 specimens, 85.7 ~ 110.7 mm standard length (SL), collected by Jia-Jun Zhou and Wei Sun in June 2021, in Suichang County, Lishui City, Zhejiang Province ( Qiantang River ) (28.5956 ° N, 119.2709 ° E) ; SHOU 202106001 – SHOU 202106003 , 3 specimens, 84.5 ~ 109.4 mm standard length (SL), collected by Yun-Feng Huang in June 2021, in Shexian County, Huangshan City, Anhui Province ( Qiantang River ) (29.8637 ° N, 118.4100 ° E) .

Diagnosis.

The new species, Opsariichthys iridescens sp. nov. can be clearly distinguished from its two sympatric congeners in the Qiantang River and nearby geographic regions (Tables 3 , 4 ). It can be distinguished from O. evolans by the following features: (1) lateral-line scales 45–52 (vs 42–45); (2) scales above lateral-line nine or ten (vs 8); (3) pre-dorsal scales 18–21 (vs 15–17); (4) two rows of pharyngeal teeth (vs 3 rows); (5) maxillary extending to or slightly beyond the vertical of anterior margin of orbit in adult male (vs never extending to the vertical of anterior margin of orbit); (6) pectoral fin extending to pelvic fin in adult male (vs extending far beyond origin of ventral fin); (7) almost uniform narrow pale cross-bars on trunk and widening significantly on caudal peduncle (vs gradually widened, Fig. 3 E, F ); (8) lower jaw with one row of large tubercles usually united basally to form a plate in male (vs 1 row of moderate tubercles well separated). The new species can be clearly distinguished from O. bidens by the following features: (1) absence of distinct anterior notch on upper lip (vs presence of conspicuous anterior notch on upper lip); (2) two rows of pharyngeal teeth (vs 3 rows); (3) maxillary extending to or slightly beyond the vertical of anterior margin of orbit in adult male (vs extending to the vertical midpoint of the eye); (4) pectoral fin extending to pelvic fin in adult male (vs never extending); (5) almost uniform narrow pale cross-bars on trunk and widening significantly on caudal peduncle (vs gradually widened, Fig. 3 C, D ); (6) one row of large tubercles under lower jaw united basally to form a plate in male (vs 3 or 4 rows of moderate tubercles well separated).

Opsariichthys iridescens sp. nov. can be well separated from the congeners: O. uncirostris from Japan and Korea; O. amurensis , O. minutus , and O. hainanensis from mainland China; O. dienbienensis and O. songmaensis from Vietnam, like O. bidens , by the absence of distinct anterior notch on upper lip (vs the presence of distinct anterior deep notch on that). Besides O. evolans , the new species can be distinguished from the remaining congeneric species: O. acutipinnis , O. chengtui , and O. macrolepis from mainland China; O. kaopingensis and O. pachycephalus from Taiwan; O. duchuunguyeni from Vietnam, that have an absence of distinct anterior notch on upper lip as well as by the following combination of morphological features (Table 4 ): (1) lateral-line scales 45–52; (2) scales above lateral line nine or ten; (3) pre-dorsal scales 18–21; (4) circum-peduncular scales 16 or 17; (5) two rows of pharyngeal teeth; (6) maxillary extending to or slightly beyond vertical of anterior margin of orbit in adult male; (7) pectoral fin extending to pelvic fin in adult male; (8) almost uniform, narrow, pale cross-bars on trunk, widening significantly on caudal peduncle; (9) nuptial tubercles on cheeks and lower jaw united basally to form a plate in adult male.

Description.

The morphometric and meristic data are listed in Tables 2 , 3 . Fig. 2 A, B shows lateral views of the male and female fish.

Dorsal fin rays iii, 7; anal fin rays iii, 9; pectoral fin rays i, 13–14; pelvic fin rays i, 7–8; lateral-line scales 45–52; scales above lateral line nine or ten; scales below lateral line three or four; predorsal scales 18–21; circum-peduncular scales 16 or 17; and two rows of pharyngeal teeth.

Body elongated and laterally compressed, belly rounded. Body depth slightly shorter than head length. No maxillary or rostral barbels. Mouth subterminal and oblique, maxillary extending to or slightly beyond the vertical of anterior margin of orbit. Mouth lacking obvious anterior notch and jaws relatively straight. Eyes rather large, upper lateral. Interorbital width approximately equal to or slightly less than snout length. Distinct nuptial tubercles on head and anal fin rays of adult male, one row of 3–6 on each side of lower jaw, one row of three or four on cheek. One row of 4–6 large, rounded tubercles on snout, usually united basally to form a plate. Body with moderately cycloid scales. Lateral line complete, depressed downward above pectoral fin and extending along lower half of body to mid-lateral on caudal peduncle. Tiny scales on belly.

Pectoral fin reaching or extending slightly beyond pelvic fin origin when depressed in adult male, but not reaching the origin in female. Pelvic fin origin vertical or slightly behind dorsal fin origin, extending to anal fin origin when depressed in adult male, but not reaching the origin in female. Anal fin rays rather elongate, especially first to fourth branched rays longer in male, with the rear tip extending beyond vertical line of caudal fin base. Caudal fin forked, lower lobe almost equal to upper one.

Coloration. In life, body brightly colored, males more colorful than females. Ten to thirteen irregular blue-green cross-bars separated by pale cross-bars on the flanks. In adult male, uniform narrow pale pink cross-bars on trunk and two on caudal peduncle widening significantly; upper and lateral sides of head grayish and transitioning to orange-red on ventral side and lower margin of cheek. Dorsal fin rays transparent and membrane black-grey with orange margin. Anal fin and caudal fin rays transparent, membrane pale yellow or colorless. Pectoral fins orange and pelvic fins yellow (Fig. 3 A ). In females, narrow bright yellow bars on trunk and always absent on caudal peduncle. Dorsal fin black-grey. Pectoral fin orange yellow. Pelvic fin, anal fin and caudal fin transparent and colorless (Fig. 3 B ). In 10 % formalin-fixed specimens, dorsal and flank of head and body grayish brown; ventral surface of head and abdomen white to yellowish. Dorsal and caudal fin dark gray. Pectoral, pelvic and caudal fin grayish white (Fig. 2 ).

Distribution.

The new species is only found in Qiantang and Oujiang River systems in Zhejiang Province and the tributaries of the lower Yangtze River adjacent to the Qiantang River.

Habitat.

The new species lives in the headwaters of streams with moderate flow velocities and clear water with small to medium-sized pebbles and boulders in the substrate (Fig. 4 ).

Etymology.

Iridescens is the Latin form of the word iridescent. Here, it refers to the unique body color, which is brighter than that of any known species in the genus. In this study, we propose the Chinese common name Hóng Cǎi Mǎ Kǒu Yú (虹彩马口鱼).

Figures

Figure 2. Opsariichthys iridescens sp. nov. A holotype, SHOU 202210001, preserved male specimen, 91.0 mm SL B paratype, SHOU 202308012, preserved female specimen, 85.2 mm SL.

Figure 3. Opsariichthys iridescens sp. nov. A live male B live female; Opsariichthys bidens C live male D live female; Opsariichthys evolans E live male F live female.

Figure 4. Image of the habitat of Opsariichthys iridescens sp. nov., near riverbed with stones.