Triplophysa ziyunensis Wu, Luo, Xiao & Zhou, 2024

Lan, Chang-Ting, Wu, Li, Luo, Tao, Liu, Ye-Wei, Zhou, Jia-Jun, Yu, Jing, Zhao, Xin-Rui, Xiao, Ning & Zhou, Jiang, 2024, Two new hypogean species of the genus Triplophysa (Osteichthyes, Cypriniformes, Nemacheilidae) from Guizhou Province, Southwest China, with underestimated diversity, ZooKeys 1214, pp. 237-264 : 237-264

Triplophysa ziyunensis Wu, Luo, Xiao & Zhou sp. nov.

Figs 4 , 5 , Table 5 , Suppl. material 1

Type material.

Holotype. GZNU 20230529001 (Fig. 4 ), 105.1 mm total length (TL), 86.7 mm standard length (SL), collected by Li Wu and Xing-Liang Wang on 29 May 2023, at Shuitang Village , Maoying Town, Ziyun County, Guizhou Province, China (25.96846238 ° N, 106.13737106 ° E; 1228 m a. s. l.; Fig. 1 ).

Paratypes. Four specimens from the same locality as the holotype: GZNU 20230226008-226010, and GZNU 20230529002, 63.3–100.1 mm SL, collected by Tao Luo, Li Wu, Xing-Liang Wang, Xin-Rui Zhao, and Chang-Ting Lan on 26 February 2023.

Diagnosis.

Triplophysa ziyunensis sp. nov. is distinguished from other hypogean species of the genus Triplophysa by the following characteristics in combination: (1) body naked, scaleless, pigmented markings on surface of body, except ventral; (2) eyes reduced, diameter 2.4–4.9 % of head length (HL); (3) pelvic-fin tip extending to anus; (4) tip of pectoral fin not reaching pelvic fin origin; (5) anterior and posterior nostrils closely set, with anterior nostril elongated to a barbel-like tip; (6) tip of outrostral barbel extending backward, not reaching anterior margin of eye; (7) lateral line complete; (8) posterior chamber of air bladder degenerated; and (9) dorsal-fin rays iii- 8, pectoral-fin rays i- 10, pelvic-fin rays i- 6, anal-fin rays iii- 5, and 16 branched caudal-fin rays.

Description.

Morphological data on the specimens of Triplophysa ziyunensis sp. nov. are provided in Table 5 and Suppl. material 1. Body elongated and cylindrical, posterior portion gradually compressed from dorsal fin to caudal-fin base, with deepest body depth anterior to dorsal-fin origin, deepest body depth 13–16 % of standard length (SL). Dorsal profile slightly convex from snout to dorsal-fin insertion, and then straight from posterior portion of dorsal-fin origin to caudal-fin base. Ventral profile flat. Head short, length 26–27 % of SL, slightly depressed and flattened, width slightly greater than depth (head width (HW) / head depth (HD) = 1.1–1.3). Snout slightly pointed, and snout length 46–50 % of HL. Mouth inferior and curved, mouth corner situated below anterior nostril, upper and lower lips smooth, lower lip with V-shaped median notch. Three pairs of barbels are present: inner rostral barbel long, length 23–27 % of HL, backward extending to corner of the mouth; out rostral barbel long, length 52–58 % of HL, backward extending to beyond posterior margin of eyes. Maxillary barbel not extending to posterior margin of operculum, length 34–42 % of HL. Anterior and posterior nostrils closely set, length 0.20–0.25 mm. Anterior nostril tube long, with an elongated short barbel-like tip, tip of posterior nostril extending backward not reaching to anterior margin of the eye. Eyes reduced, with diameter 2–5 % of HL. Gill opening small, gill rakers not developed, ten inner gill rakers on first gill arch (n = 1).

Dorsal-fin rays iii- 8, pectoral-fin rays i- 10, pelvic-fin rays i- 6, anal-fin rays i- 5, 16 branched caudal-fin rays. Dorsal fin short, length 20–23 % of SL, distal margin emarginated, origin anterior to pelvic-fin insertion and situated slightly posterior to the midpoint between snout tip and caudal-fin base, first branched ray longest, shorter than head length, tip of dorsal fin vertical to the anus. Pectoral fin moderately developed, length 22–24 % of SL, tip of pectoral fin extending backward almost to midpoint between origin of pectoral and pelvic fin origins, not reaching to pelvic fin origin. Pelvic fin length 16–20 % of SL, vertically aligned with third branched ray of dorsal fin, tips of pelvic fin reaching anus. Anal fin length 16–20 % of SL, distal margin truncated, origin close to anus, tips of anal fin not reaching caudal-fin base, distance between tips of anal fin and anus 8.5 × the eye diameter. Caudal fin forked, upper lobe equal in length to lower lobe, tips pointed, caudal peduncle length ~ 13.6 mm, caudal peduncle depth ~ 5.8 mm, with weak adipose crests along both dorsal and ventral sides. Total vertebrae: 39 (n = 1).

Cephalic lateral line system developed. Lateral line complete, exceeding tip of pectoral fin and reaching base of caudal fin. Two chambers of air bladder, anterior chamber dumbbell-shaped and membranous, open on both sides, slightly closed posteriorly; posterior chamber degenerated, slightly filling the body cavity, connected with anterior chamber by a long, slender tube.

Coloration.

In cave water, the body of living fish is semi-translucent and pale pink, with irregular dark brownish brown patches on the head and body (Fig. 5 ). After fixation in 10 % formalin solution, the body color was pale grey, and the dark-brown patches on the head and body were more prominent (Fig. 4 ).

Secondary sex characteristics.

No secondary sex characteristics were observed based on the present specimens of Triplophysa ziyunensis sp. nov.

Comparisons.

Detailed comparative morphological data of Triplophysa ziyunensis sp. nov. with the 39 recognized hypogean species of Triplophysa are given in Table 2 . Triplophysa ziyunensis sp. nov. is genetically close to T. qingzhenensis , T. rosa , and T. wudangensis and shares some similar morphological characters, such as reduced eye degeneration and degenerated body pigmentation, pigmented markings on the body surface, except ventral, but can still be distinguished by a combination of some morphological characters.

Triplophysa ziyunensis sp. nov. is be distinguished from T. qingzhenensis and T. wudangensis by having 10 branched pectoral fin rays (vs 8–9), 6 branched pelvic-fin rays (vs 5), 16 branched caudal fin rays (vs 14–15), and inhabiting the Pearl River basin (vs Yangtze River basin).

Triplophysa ziyunensis sp. nov. can be distinguished from T. rosa by having reduced body pigmentation, pigmented markings on body surface, except ventral (vs absence), eyes reduced, diameter 2.4–4.9 % of HL (vs absent), 8 branched dorsal fin rays (vs 9), 10 branched pectoral fin rays (vs 12), 6 branched pelvic-fin rays (vs 7), 16 branched caudal fin rays (vs 14), and inhabiting the Pearl River basin (vs Yangtze River basin).

Ecology and distribution.

Triplophysa ziyunensis sp. nov. has only been found in one cave in Shuitang Village, Maoying Town, Ziyun County, Guizhou Province, China, at an elevation of 1134 m. The pool where the new species was found is more than 15 m long, 13 m wide, and ~ 3 m deep, with a slow flow of water, and is located 80 m further inside the entrance of the cave. Inside the cave, another fish ( Sinocyclocheilus multipunctatus , three individuals), bats ( Rhinolophus sp. , five individuals), and frogs ( Odorrana wuchuanensis , 11 individuals) were found. Outside the cave, rapeseed and peppers were being grown. The population of the new species is very small and only five specimens were collected.

Remarks.

The new species, Triplophysa ziyunensis sp. nov., inhabits the underground rivers of the type locality. Eyes are present and reduced, and with irregular dark brownish brown patches on the head and body. Therefore, this species can be considered as a stygophile fish within the hypogean group of the genus Triplophysa .

Etymology.

The specific epithet ziyunensis refers to the type locality of the new species: Shuitang Village, Maoying Town, Ziyun County. We propose the common English name “ Ziyun high-plateau loach ” and the Chinese name “ Zǐ Yún Gāo Yuán Qīu (紫云高原鳅) ”.

Figures

Figure 1. Sample collection localities and distributions of the two new species and 39 hypogean species of the genus Triplophysa in southern China. The base maps are from the Standard Map Service website (http://bzdt.ch.mnr.gov.cn/index.html).

Figure 4. Morphological characteristics of holotype GZNU 20230529001 of Triplophysa ziyunensis sp. nov. in preservative (10 % formalin) A dorsal view B ventral view C lateral view D dorsal view of head E lateral view of head, and F ventral view of head.

Figure 5. Ecological photographs of Triplophysa ziyunensis sp. nov. and closely related species in life A Triplophysa ziyunensis sp. nov. B T. rosa C T. wudangensis, and D T. qingzhenensis, from Dr. Zhi-Xuan Zeng.