Triplophysa xiuwenensis Zhu, Zhang & Yuan, 2025

Zhu, Ting-Ting, Yuan, Feng-Hua, Zhang, Ren-Yi & Zhao, Ya-Hui, 2025, A new cave-dwelling species of the genus Triplophysa (Cypriniformes, Nemacheilidae) from southwest China, Zoosystematics and Evolution 101 (4), pp. 1383-1396 : 1383-1396

Triplophysa xiuwenensis Zhu, Zhang & Yuan sp. nov.

Figs 1 , 2 , 3 , 4 , Table 2

Holotype.

GZNUSLS 202306086 (Fig. 1 ), 69.1 mm SL, collected by Ren-Yi Zhang, Lei Deng, Huan Cheng, Ren-Rong Huang on June 23, 2023, in Shilin Village , Dashi Buyi Township, Xiuwen County, Guizhou Province, China (27.055334°N, 106.476045°E; ca. 1114 m; Fig. 4 ).

Paratypes.

Four specimens from the same locality as the holotype. GZNUSLS 202306088 –090, 40.5–58.2 mm SL, ASIZB 248338 , 56.3 mm SL, the collected information is the same as that of the holotype specimen .

Diagnosis.

The new species 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 4.6–6.7 %; anterior nostril with elongated barbel-like tip; long outer rostral barbel reaching to posterior margin of eyes; distal margin of dorsal fin truncate; tip of pectoral fin not reaching to pelvic-fin origin, tip of pelvic fin near anus; dorsal fin 8, anal fin 6, and caudal fin 14–15 branched fin rays; vertebrae 41.

Description.

D iii, 8; A iii, 6; P i, 9; V i, 6; C 14–15; vertebrae 4 + 37 (n = 1).

Morphological data of the specimens of Triplophysa xiuwenensis sp. nov. are given in Table 2 .

Body elongated, with anterior being nearly cylindrical and posterior portion flattened laterally from dorsal-fin base to caudal-fin base increasingly. With deepest body depth anterior to dorsal-fin origin, deepest body depth 12.8–14.8 % of SL. Dorsal-fin origin near body midpoint. Dorsal profile slightly convex from snout to dorsal-fin insertion, then gradually compressed from dorsal fin origin to caudal fin base. Ventral side flat. Head conical, slightly flattened and head length 23.6–28.6 % of SL. Width greater than height. Snout short, tip blunt. Anterior and posterior nostrils closely connected, anterior nostril in a short tube with an elongated barbel-like tip, the tip of the nostril appendage not reaching the anterior margin of the eye; posterior nostril above maxillary barbel. Eye reduced to black dot, located dorsolaterally on head, orbit indistinct, eye diameter 4.6–6.7 % of HL.

Three pairs of barbels; inner rostral barbel short, 15.3–23.4 % of HL, extending backward not reaching front of eye; outer rostral barbel well-developed, 31.0–53.2 % of HL, extending backward reaching beyond eye; maxillary barbel 30.0–37.8 % of HL, extending backward reaching beyond eye. Mouth inferior, mouth angle located below midpoint between anterior and posterior nostrils. Central lower lip with ‘ V’ - shaped notch, interrupted centrally, forming one pair of longitudinal folds. Upper jaw arched, no median dentiform process; lower jaw arched, no central notch. Gill filaments with tufted branching, gill rakers short, with small protuberances.

Body smooth and scaleless. Lateral line pores on head indistinct, connecting posteriorly with lateral line on body; body lateral line complete, straight, extending to slightly anterior of base of caudal peduncle. The posterior chamber of air bladder degenerated.

Dorsal fin origin located near midpoint or slightly anterior between snout tip and caudal fin base; dorsal fin short, 21.3–24.5 % of SL, with straight margin. First branched fin ray longest, shorter than head length, extending past vertical of anus, approaching vertical of anal fin origin. Pectoral fin spread flat, fin ray tips reaching about halfway between pectoral and pelvic fin origins. Pelvic fin spread flat, origin posterior to dorsal fin origin, fin ray tips extending near anus but not reaching anal fin origin; distance between pelvic and pectoral fin origins greater than distance to anal fin origin. Anal fin margin concave, fin ray tips not reaching caudal fin base. Anus close to anal fin origin. Caudal fin forked, upper lobe slightly longer than lower lobe, tips slightly pointed, caudal peduncle with slight adipose crest.

Coloration.

Live adults of the new species exhibit a pale yellow body coloration, no pigmentation, fin bases pale yellow, membranes between fins colorless. No spots on body (Fig. 3 ). After fixation in 10 % formalin, body turns creamy white (Fig. 1 ).

Sexual dimorphism.

No secondary sexual characteristics were detected in the current samples.

Distribution.

The specimens were collected at the outlet of a karst cave in Shilin Village, Xiuwen County, Guizhou Province, China, where the water is connected to the upper reaches of the Wujiang River system in the Yangtze River basin (Fig. 4 ). So far, Triplophysa xiuwenensis sp. nov. has only been found in the type locality.

Etymology.

The specific name refers to the type locality of the new species: Shilin Village, Xiuwen County and the Latin suffix (ensis). We propose the Chinese name ‘ 修文高原鳅’.

Molecular phylogenetic analysis

We constructed a phylogenetic tree of Triplophysa based on the mitochondrial Cyt b molecular marker. Within the hypogean group clade, two specimens from Shilin Village, Xiuwen County, Guizhou Province, formed a distinct branch that is a sister group to T. rosa , T. wudangensis , T. qingzhenensis , and T. ziyunensis (Fig. 5 ). Based on the K 2 P model, pairwise genetic distances between the new species and its congeners are given in Table 5 . The new species shows a minimum genetic distance of 2.2 % from other Triplophysa species (vs. T. qingzhenensis ). Therefore, the species from this locality represents a new evolutionary lineage, which we describe as a new species: Triplophysa xiuwenensis sp. nov.

Figures

Figure 1. Triplophysa xiuwenensis sp. nov., holotype, GZNUSLS 202306086, 69.1 mm SL. a. dorsal view; b. lateral view; c. ventral view.

Figure 2. Triplophysa xiuwenensis sp. nov., holotype, micro-CT graph. a. dorsal view; b. lateral view; c. ventral view.

Figure 3. Live specimen of Triplophysa xiuwenensis sp. nov.

Figure 4. The distribution of Triplophysa xiuwenensis sp. nov.

Figure 5. Phylogenetic relationships of selected species of Triplophysa and three outgroup species based on Bayesian inference (BI) methods using mitochondrial Cyt b gene sequences. The BI posterior probabilities are shown at the nodes.