Two new cave-dwelling species of Triplophysa (Cypriniformes, Nemacheilidae) from Guizhou, China

Two new cave-dwelling species, Triplophysa zhijinensis sp. nov. and Triplophysa dafangensis sp. nov., are described from karst caves in Guizhou Province, southwestern China. Triplophysa zhijinensis sp. nov. is distinguished from other hypogean congeners by body scaleless, dorsal with pigment spots, lateral line complete; eye degenerated into small black spot or disappears, anterior nostril with barbel-like tip; distal margin of dorsal fin truncate; tip of pelvic fin not reaching to anus. Triplophysa dafangensis sp. nov. is distinguished from other hypogean congeners by body naked, without skin pigmentation, lateral line complete; eye reduced, with diameter of head length 5.3-7.1%; outer rostral barbel reaching to or beyond posterior margin of posterior nostrils; distal margin of dorsal fin truncate; tip of pectoral fin not reaching to pelvic-fin origin. To further validate their taxonomic status, mitochondrial cytochrome b (Cyt b) gene sequences were used to reconstruct phylogenetic relationships and assess genetic distances. The molecular data corroborate the morphological findings and support the recognition of both species as distinct evolutionary lineages. These discoveries highlight the underestimated diversity of Triplophysa in subterranean habitats and emphasize the ecological importance of karst groundwater systems as sheltered habitats for specialized cave-adapted fauna.