Abstract:Troglonectes Zhang, Zhao & Tang 2016 fish included 10 species, all were small cave freshwater fish endemic to China, original records showed that most species (7 species) distributed in underground rivers in the Karst areas of Guangxi, few species (3 species) recorded in Guizhou Province, China. Four loach specimens of genus Troglonectes were collected during cave biodiversity survey from 2018 to 2019 within Xiaoqikong scenic area, Libo County, Guizhou Province, China (Table 1). Through the morphological comparison, it was found that similar to T. barbatus (Table 3), the key morphological taxonomic characteristics showed the same, such as: dorsal fin rays, pelvic fin rays and caudal fin rays; phylogenetic tree analysis and genetic distance analysis based on the mitochondrial 16S rRNA and Cyt b reconstruction showed that four specimens were clustered into a highly supported clade with T. barbatus from the type locality (Fig. 2); genetic distances of 16S rRNA and Cyt b calculated based on Kimura 2-parameter showed that the genetic distances between these specimens and T. barbatus were 0.4% and 0.2%, respectively, which were much smaller than those congeners of genus Troglonectes (genetic distances of 16S rRNA was 2.4%, and Cyt b was 6.1%) (Table 2). In this study, 16S rRNA and Cyt b molecular markers were used to study the phylogenetic relationship and genetic distances of genus Troglonectes. The comprehensive morphological and phylogenetic analyses indicated that four specimens were belonged to the weakly bearded cave loach of the genus Troglonectes Loach, family Carabidae, new distribution record of Troglonectes fishes in Guizhou Province.