Yunnanilus mentibarbatus, a new species of loach from Yunnan, China (Cypriniformes, Nemacheilidae)

A new loach species, Yunnanilus mentibarbatus sp. nov., is described from Yunnan Province, China. The new species differs from other congeneric species by the following combination of characters: lateral line incomplete; a pair of whisker-like fleshy projections on the chin in females; processus dentiformis present; eye diameter shorter than interorbital width; eye diameter 16.3 % – 23.2 % of HL; 11 inner gill rakers on the first gill arch; 16 branched caudal-fin rays; head length 23.7–26.5 % of standard length; caudal peduncle length 15 % – 17.8 % of SL.

Bayesian inference phylogenetic analysis based on mitochondrial COI and cytochrome b (Cyt b) provides strong support for the validity of Yunnanilus mentibarbatus sp. nov. Sexually dimorphic characters within Yunnanilus — such as dioecious coloration and specialized morphology, including tubercles on the trunk, temporal tubercles on the caudal peduncle of nuptial males, and whisker-like fleshy protuberances on the chin of females of the new species — may be related to the breeding season.

Anthropogenic factors such as eutrophication of water and disappearance of aquatic plants are leading to the decline of Yunnanilus species. This highlights the importance of protecting the biodiversity of Yunnanilus.