Tibetan Loach of the genus Triplophysa are the most common members of the Stone Loach family, Nemacheilidae, found on the Qinghai-Tibet Plateau. These fish are found in almost all water bodies in the region, with new species of Triplophysa still being reported regularly. As a result, a total of 147 valid species of Triplophysa have been recorded to date, including Triplophysa zhaoi, which is found living in the swamps of the Lükqün Oasis in the Turpan Depression, at an altitude of 50 m below sealevel, making it the lowest living freshwater Fish in Asia, and Triplophysa stolickai which is found in hot springs near the Longmu Lake in western Tibet, at an altitude of 5200 m, making it the highest altitude Fish in Asia, and possibly the highest altitude Fish in the world.
In a paper published in the journal Zoological Research in July 2020, Chen-Guang Feng of the Key Laboratory of Adaptation and Evolution of Plateau Biota of the Northwest Institute of Plateau Biology of the Chinese Academy of Sciences, and the School of Ecology and Environment at the Northwestern Polytechnical University, Yu Zhang, also of the Key Laboratory of Adaptation and Evolution of Plateau Biota, and of the University of the Chinese Academy of Sciences, Chao Tong, again of the Key Laboratory of Adaptation and Evolution of Plateau Biota, and of the Biology Department at the University of Pennsylvania, Bing-Zheng Zhou and Xiao-Hui Li, again of the Key Laboratory of Adaptation and Evolution of Plateau Biota, and of the University of the Chinese Academy of Sciences, Yong-Tao Tang, again of the Key Laboratory of Adaptation and Evolution of Plateau Biota, and of the College of Fisheries at Henan Normal University, and Wen-Zhu Song and Kai Zhao, once again of the Key Laboratory of Adaptation and Evolution of Plateau Biota, describe a new species of Tibetan Loach from the Weihe River in Gansu Province, China.
Weihe River is a tributary of the Yellow River and originates from the southern part of Gansu Province. Previous studies have reported that southern Gansu is a hotspot area for Triplophysa, with an extensive distribution of species across the river systems. Until now, 17 species of Triplophysa have been reported from the Yellow River system, five of which have been recorded from Weihe River. Following an investigation of Triplophysa species from Weihe River, 15 specimens superficially resembling Triplophysa stoliczkae were collected and are described as a new species based on morphological and molecular analyses.
Map showing sampling sites of Triplophysa weiheensis (star symbol, solid star for type locality). (1) Zhang River, at Chenjiamo Village, Zhangxian County; (2) Niutou River, at Hongbao Town, Qingshui County; (3) Niutou River, at Maiji District, Tianshui City. Feng et al. (2020).
Previous research has reported that Triplophysa stoliczkae is a striking case of morphological convergence and consists of distinct lineages that are not close relatives. As there has been no formal taxonomic revision for Triplophysa stoliczkae, Feng et al. treated it as a morphological species in this study but considered its different genetic lineages in phylogeny. These lineages, which were initially mistaken as Triplophysa stoliczkae, exhibit very similar morphology. Thus, they represent a known morphological unit in the genus Triplophysa. Feng et al. specifically measured 61 Triplophysa stoliczkae specimens collected from various water systems and used principal component analysis to visualize morphological differences between Triplophysa stoliczkae and the new species.
The new species is named Triplophysa weiheensis, where 'weiheensis' means from the Weihe River. The body of Triplophysa weiheensis is thick and cylindrical. The dorsal profile of the body is arch-like. Maximum depth of body slightly greater than maximum width, occurring between pectoral and dorsal fins. Caudal peduncle laterally compressed, depth nearly uniform toward caudal-fin base, length longer than head length. Head width greater than depth. Cheeks slightly inflated, V-shaped outline in ventral view. Snout obtuse, sloping downward anterior to anterior nostril. Snout length shorter than postorbital length. Anterior and posterior nostrils close together. Valves around anterior nostrils, but not around posterior. Eyes small, dorsolaterally in head. Interorbital space wide. Mouth inferior. Lips thick and well-developed with furrows; lower lip continuous with shallow median incision. Lower jaw crescentic, uncovered by lower lip. Three pairs of barbels thick, moderately short; inner rostral barbels almost reaching corner of mouth; outer rostral barbels horizontally reaching posterior nostril; maxillary barbels horizontally reaching mid-point of eyes.
Lateral view, dorsal view, and ventral view of Triplophysa weiheensis, NWIPB 1505189, holotype, 65.8 mm. Feng et al. (2020).
Fins short, dorsal fin rounded distally, originating anterior to pelvic-fin origin; dorsal-fin origin near midway between tip of snout and caudal-fin base or slightly nearer to caudal-fin base. Pectoral fin short, not reaching halfway point to pelvic-fin base. Pelvic fin reaching past anus, distal fin tip attaining anal-fin origin when adpressed. Anal fin rounded distally, just posterior to anus. Caudal fin slightly emarginate.
Lateral view of Triplophysa weiheensis, NWIPB 1505189, holotype, 65.8 mm (a) and Triplophysa stoliczkae NWIPB 1707001, 85.1 mm, from the Yellow River system (b). Feng et al. (2020).
Skin scaleless. Lateral line tapering, interrupted on posterior trunk at pelvic-fin distal extremity; few lateral line pores close to caudal-fin base. Stomach U-shaped, expanded. Intestine long, with 6–7 loops, one hidden loop surrounded by 5–6 loops). Bony capsule of air bladder small and thin, closed laterally; posterior chamber of air bladder absent.
Micro computerised tomograph of skeletal system of Triplophysa weiheensis NWIPB 1505183, paratype, 64.1 mm. Feng et al. (2020).
In mature males, unbranched and four outer branched pectoral-fin rays thickened, covered with breeding tubercles on dorsal surface. Small breeding tubercles also present on both sides of head in liber apophyses extending from anterior lower margin of orbit to base of outer rostral barbel. These characters do not occur in females.
Sexual dimorphism of Triplophysa weiheensis. Dimorphic characters are highlighted in red circles. Feng et al. (2020).
Specimens were collected from flowing streams with gravel or sandy substrates at 1360–1768 m above sealevel. River water became muddy at about 0.5 m deep. Periphytic Algae, sand, and Insect larvae (e.g. Chironomids) were found in the stomach of specimens. Other species collected with Triplophysa weiheensis included Triplophysa dalaica, Triplophysa minxianensis, Pseudorasbora parva, Gobio huanghensis.
Habitat of Triplophysa weiheensis. (a) Type locality: Zhang River, at Chenjiamo Village, Zhangxian County; (b) Niutou River, at Hongbao Town, Qingshui County. Kai Zhao in Feng et al. (2020).
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