Xie's golden-lined fish (Sinocyclocheilus xiejiahuai) lives in cave with extremely small population

NEWS - Xie’s golden-lined fish (Sinocyclocheilus xiejiahuai) lives in a cave with a type site in the Nanpanjiang River Basin. A phylogenetic tree reconstructed based on mitochondrial genes suggests that the new species is an independent evolutionary lineage with 1.9-13.8% genetic divergence in mitochondrial Cyt b from its conspecifics.

During a biodiversity survey in a completely dark cave in Hongguo Town, Panzhou City, southwest Guizhou Province, China, in October 2019, researchers collected a Sinocyclocheilus specimen with normal eyes, no scales, and no irregular black markings on the flanks.

S. xiejiahuai is the only vertical cave species found at an elevation of 2276 m. The location is in the Beipanjiang River Basin and there is no light in the cave. The individuals are scattered in a pool from the cave entrance.

The pool is ~1.8 m wide, 80 cm deep, with a water temperature of ~16C and a pH of 7.4. Inside the cave, the species S. xiejiahuai is symbiotic with S. longicornus (S. angularis group) and Triplophysa panzhouensis. The agricultural land outside the cave is mostly planted with corn, wheat and potatoes.

The specimen was identified into the S. tingi group based on morphological characters and molecular examination showed that the specimen was an undescribed species. However, between 2019-2023 the researchers conducted 16 more surveys in the same cave and did not reveal any new individuals.

The new species is placed in the S. tingi species group and can be clearly distinguished from the S. angularis, S. cyphotergous, S. microphthalmus and S. jii groups due to the absence of horn-like structures and an indistinct elevation at the head-dorsal junction, short pectoral fins that do not reach the base of the pelvic fins, with serrations along the posterior edge of the last dorsal fin that is not branched.

The new species is distinct from S. aluensis, S. angustiporus, S. bannaensis, S. grahami, S. guishanensis, S. huaningensis, S. huizeensis, S. lateristriatus, S. longshanensis, S. macrocephalus, S. maculatus, S. maitianheensis, S. malacopterus, S. oxycephalus, S. purpureus, S. robustus, S. wumengshanensis, S. xichouensis, S. tingi, S. yimenensis and S. wenshanensis by the absence of irregular markings on the body sides.

It is distinct from S. anophthalmus by the presence of eyes (vs. absent) and 74 lateral line pores (vs. 52–56). Distinguished from S. longifinus, S. qujingensis, and S. yangzongensis by 6 branched dorsal fin rays (vs. 7) and 7 branched pelvic fin rays (vs. 8 or 9).

Distinguished from S. qujingensis and S. yangzongensis by 13 branched pectoral fin rays (vs. 16) and from S. longifinus by pectoral fin tips not reaching pelvic fin base (vs. reaching pelvic fin base).

Distinguished from S. luolouensis by normal eyes (vs. reduced eyes) and pectoral fin tips not reaching pelvic fin origin (vs. extending beyond pelvic fin origin). Distinguished from S. gracilis by having nine combs on the first gill arch (vs. 12) and body depth 13% of standard length (vs. 21.0-23.8%).

Distinguished from S. pingshanensis and S. gracilis by serrations along the posterior margin of the last dorsal fin that are unbranched (vs. none) and 9 combs on the first gill arch (vs. 10-12). Distinguished from S. wui by 3 unbranched anal fin rays (vs. 2), 13 branched pectoral fin rays (vs. 14-15) and 17 branched caudal fin rays (vs. 14-15).

The specific name xiejiahuai is given in honor of Professor Jia-Hua Xie (谢家骅) for his contributions to zoological research in China. He described S. angustiporus and his work has made important contributions to the study of zoology, especially the conservation of endangered species. The researchers proposed the common names “Xie’s Golden-lined Fish” and “Xiè Shì Jīn Xiàn Bā (谢氏金线鲃).”

The researchers have conducted a total of 16 field surveys at the type site over the past 5 years and no new individuals have been detected except for the first one. They recommend Endangered status on the IUCN Red List of Threatened Species due to the small population size and threats to the habitat including lowering water levels in the cave, pesticide use, domestic waste and rapid urbanization.

Original research

Fan C, Wang M, Wang J-J, Luo T, Zhou J-J, Xiao N, Zhou J (2024) Sinocyclocheilus xiejiahuai (Cypriniformes, Cyprinidae), a new cave fish with extremely small population size from western Guizhou, China. ZooKeys 1214: 119-141, DOI:10.3897/zookeys.1214.127629

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