A new loach species, Oreonectes zhangisp. nov., was identified from Xingye County, Yulin City, Guangxi, China. The species can be distinguished from all other congeners by a combination of the following characters: six branched pelvic-fin rays; a reduced posterior chamber of air-bladder; vertebrae 4 + 32; the tip of the male pelvic fin does not reach the anus. Molecular analyses using the Cyt b gene showed that the new species forms a monophyletic group and is closely related to O. damingshanensis.

China’s southwestern karst landscapes support remarkable cavefish diversity, especially within Sinocyclocheilus, the world’s largest cavefish genus. Using integrative taxonomic methods, we describe Sinocyclocheilus wanlanensis sp. nov., found in a subterranean river in Guizhou Province. This species lacks horn-like cranial structures; its eyes are either reduced to a dark spot or absent. It possesses a pronounced nuchal hump and a forward-protruding, duckbill-shaped head. Morphometric analysis of 28 individuals from six species shows clear separation from related taxa. Nano-CT imaging reveals distinct vertebral and cranial features. Phylogenetic analyses of mitochondrial cytb and ND4 genes place S. wanlanensis within S. angularis group as sister to S. bicornutus, with p-distances of 1.7% (cytb) and 0.7% (ND4), consistent with sister-species patterns within the genus. Sinocyclocheilus wanlanensis is differentiated from S. bicornutus by its eyeless or degenerate-eye condition and lack of bifurcated horns. It differs from S. zhenfengensis, its morphologically closest species, in having degenerate or absent eyes, shorter maxillary barbels, and pelvic fins that reach the anus. The combination of morphological and molecular evidence supports its recognition as a distinct species. Accurate documentation of such endemic and narrowly distributed taxa is important for conservation and for understanding speciation in cave habitats.

Sinocyclocheilus microphthalmus is endemic to Youjiang River and Hongshuihe River systems in Guangxi, Southwestern China. In this study, the complete mitochondrial genome of S. microphthalmus was sequenced. It was determined to be 16,589 bases. The overall base composition was 31.87% A, 24.96% T, 27.19% C, 15.99% G with 43.17% GC content. The nucleotide sequence data of 12 heavy-strand protein-coding genes of S. microphthalmus and other 13 Sinocyclocheilus species were used for phylogenetic analyses. Trees constructed using Bayesian inference showed a topology demonstrating that Sinocyclocheilus species clustered as one monophyletic clade with strong supports.