Ziyun high-plateau loach (Triplophysa ziyunensis) and King Yalu high-plateau loach (Triplophysa yaluwang)

NEWS - Ziyun high-plateau loach (Triplophysa ziyunensis) and King Yalu high-plateau loach (Triplophysa yaluwang) inhabit underground rivers with reduced eyes and irregular brown spots as stygophile fishes in the hypogean group of the genus Triplophysa in Maoying Town, Ziyun County, Guizhou Province, China.

Mitochondrial cyt b revealed 1.4-2.0% genetic divergence between the two new species and their close relatives. The nuclear gene RAG1 showed that the two species had unique haplotypes with few linking mutations. This study emphasizes the importance of nuclear genes for identifying cave species undergoing rapid speciation with little genetic divergence due to mitochondrial introgression between species.

T. ziyunensis is genetically close to T. qingzhenensis, T. rosa and T. wudangensis and has some similar morphological characters, such as eye degeneration, decreased body pigmentation, pigmented markings on the body surface except the ventral, but can still be distinguished by a combination of several morphological characters.

This species is 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).

Different from T. rosa by having reduced body pigmentation, pigmented markings on the body surface, except the ventral part (vs. none), eyes diameter 2.4-4.9% of HL (vs. none), 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).

The specimen was only found in a cave in Shuitang Village, Maoying Town, Ziyun County, Guizhou Province, China, at an elevation of 1134 meters. Living in a pond with a length of more than 15 meters, a width of 13 meters, a depth of ~3 meters, slow water flow and 80 meters further inside the cave entrance.

Inside the cave, other fish (Sinocyclocheilus multipunctatus), bats (Rhinolophus sp.) and frogs (Odorrana wuchuanensis) were found. Outside the cave, rapeseed and pepper plants were being planted. The population of this new species is very small and only 5 specimens were collected.

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

T. yaluwang is genetically close to T. guizhouensis, T. longliensis and T. sanduensis, but can be distinguished in combination with morphological characteristics. It differs from T. ziyunensis by having a notched (vs. truncated) distal dorsal fin margin, a total of 40 vertebrae (vs. 39), 7 branched dorsal fin rays (vs. 8), 9 branched pectoral fin rays (vs. 10) and 14 branched caudal fin rays (vs. 16).

Different from T. longliensis with eye diameter 4.6-6.1% of HL (vs. 9.5-11.5%), interorbital width 24.3-26.0% of HL (vs. 31.4-37.5), total vertebrae 40 (vs. 42), posterior air sac chamber degenerated (vs. developed), 7 branched dorsal fin rays (vs. 8), 9 branched pectoral fin rays (vs. 10), and 14 branched caudal fin rays (vs. 15-16).

Different from T. sanduensis with eye diameter 4.6-6.1% of HL (vs. 11.9-15.4%), interorbital width, 24.3-26.0% of HL (vs. 31.2-40.2), total vertebrae 40 (vs. 41), dorsal fin rays, iii, 7 (vs. ii, 8-9), 3 anal fin rays unbranched (vs. 1), 14 caudal fin rays branched (vs. 17-18) and pelvic fin tips reaching the anus (vs. not reaching the anus).

Different from T. guizhouensis with eyes diameter 4.6-6.1% of HL (vs. 9.4-12.1%), distal dorsal fin margin notched (vs. truncated), body scaleless (vs. body sparsely scaled), posterior air sac chamber degenerated (vs. developed), 7 dorsal fin rays branched (vs. 8), 5 anal fin rays branched (vs. 6) and pelvic fin tips reaching anus (vs. not reaching anus).

This species was found in a cave far from Xinzhai Village, Maoying Town, Ziyun County, Guizhou Province, China, in a water system where an underground river is a tributary of the Hongshui River. The cave habitat is a vertical shaft with an entrance in the middle of a mountain slope.

The underground river is 150 meters deep from the entrance and the accessible part is about 200 meters long, 3 meters wide and 1-2 meters deep. In this cave, the new species is sympatric with Sinocyclocheilus multipunctatus and several spiders.

The specific epithet yaluwang is derived from King Yalu, a hero of the Miao people in Ziyun County, where the type site is located. He was the 18th-generation leader of the Miao ancestors. The researchers propose the common name in English “King Yalu high-plateau loach” and the Chinese name “Yà Lǔ Wáng Gāo Yuán Qīu (亚鲁王高原鳅)”.

Original research

Lan C-T, Wu L, Luo T, Liu Y-W, Zhou J-J, Yu J, Zhao X-R, Xiao N, Zhou J (2024). Two new hypogean species of the genus Triplophysa (Osteichthyes, Cypriniformes, Nemacheilidae) from Guizhou Province, Southwest China, with underestimated diversity. ZooKeys 1214: 237-264, DOI:10.3897/zookeys.1214.122439

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