Triplophysa dafangensis sp. nov.

Figs 5, 6, 7, 8, Tables 2, 3

Type material.

Holotype. • GZNUSLS 202501291 (Fig. 6), 73.0 mm SL, collected by Ren-Yi Zhang, Ting-Ting Zhu, Lei-Shan Wang, Feng-Hua Yuan, and local people on January 7, 2025, in Zengjiazhai Village, Yuchong Town, Dafang County, Guizhou Province, China (27.4232°N, 105.9309°E; ca 1530 m; Fig. 5). Paratypes. • Six specimens from the same locality as the holotype. GZNUSLS 202501288 –290, 37.6–71.9 mm SL, GZNUSLS 202501292 –294, 48.1–52.6 mm SL, the collection data are the same as that of the holotype specimen.

Diagnosis.

Triplophysa dafangensis sp. nov. can be distinguished from all other species in the genus Triplophysa by the following combination of characteristics: body naked, without skin pigmentation, lateral line complete; eye reduced, with diameter of HL 5.3–7.1 %; long outer rostral barbel reaching to or beyond posterior margin of posterior nostrils; distal margin of dorsal fin truncate; tip of pectoral fin not reaching to pelvic-fin origin, tip of pelvic fin beyond anus; dorsal fin 8, anal fin 7, and caudal fin 16 branched fin rays; vertebrae 43 (Fig. 7).

Description.

D iii, 8; A iii, 7; P i, 9; V i, 6; C 16; vertebrae 4 + 39 (n = 1).

Body elongated; anterior trunk nearly cylindrical, posterior trunk laterally compressed. Head widest at operculum. Dorsal profile of head gradually rising; dorsal body profile elevated. Ventral profile from snout to origin of anal fin nearly straight. Body depth greatest just before origin of dorsal fin, slightly decreasing toward caudal base, body depth 12.9–15.8 % of SL. Body smooth and scaleless; lateral line complete.

Head conical; cephalic lateral-line system well developed, 24.3–26.6 % of SL. Head width slightly greater than head height; head widest at operculum. Highest point of head at posterior region. Snout pointed, slightly blunt at tip; snout length slightly shorter than postorbital head length, accounting for a percentage of head length. Eyes degenerated; eye diameter 5.3–7.1 % of head length; interorbital width 33.4–38.4 % of head length. Anterior and posterior nostrils connected; anterior nostril located on apex of barbel-like nasal flap; posterior nostril opening slightly larger.

Mouth inferior, U-shaped. Lips thick, with small papillae on upper lip. Median notch present on lower lip; upper lip entire. Three pairs of barbels well developed: inner rostral barbel, outer rostral barbel, and maxillary barbel. Outer rostral barbels longest, inner rostral barbels shortest. Inner rostral barbels not reaching anterior nostrils, 19.3–26.5 % of head length; outer rostral barbels extending to or beyond posterior margin of posterior nostrils, 38.6–52.2 % of head length; maxillary barbels reaching or slightly beyond posterior margin of eyes, 30.8–38.2 % of head length. Posterior chamber degenerated; with the bony capsule forming a dumbbell shape.

Dorsal fin truncate posteriorly, 18.3–21.4 % of SL. First branched ray longest, extending beyond vertical through anus, approaching vertical through anal fin origin. Anal fin well developed, posterior margin concave, 16.1–17.2 % of SL; fin rays not reaching caudal-fin base. Pectoral fins well developed, 18.1–21.7 % of SL, horizontally extended tips not reaching pelvic fin origin. Pelvic fins well developed, 14.7–16.6 % of SL, horizontally extended origin slightly posterior to dorsal fin origin or opposite; tips extending beyond anus but not reaching anal fin origin; distance between anus and anal fin origin ~ 1 mm. Caudal fin deeply forked; upper lobe longer than lower lobe; tips slightly pointed. A low ridge-like adipose fin fold present on upper side of caudal peduncle.

Coloration.

In life, species pinkish-white in natural habitat, semi-transparent skin, body, and fin rays unpigmented, no markings (Fig. 8). After fixation in formalin, specimen pale yellow, body, and fin rays remain unpigmented (Fig. 6).

Sexual dimorphism.

No secondary sexual characteristics were observed in the collected specimens.

Distribution.

This new species was harvested from an underground river in a karst cave in Yuchong Township, Dafang County, which is halfway up a mountain near the Youshan River Scenic Area (Fig. 5). Local inhabitants have accessed the cave. The underground river is connected to the Erdao River, a tributary of the Chishui River. This is the first occurrence of a stygobitic species of Triplophysa within the Chishuihe River basin, indicating a healthy ecological environment in the region.

Etymology.

The specific name refers to the type locality (county) of the new species: Dafang County and the Latin suffix (ensis). We propose the Chinese name ‘ Dà fāng Gāo yuán qiū’ (大方高原鳅).