Integrative taxonomy reveals a new species of Acrossocheilus (Cypriniformes, Cyprinidae) from Hunan Province, China

The genus Acrossocheilus (Cyprinidae), which occurs in Southeast Asia and southern China, is of significant ecological and economic importance. A new species, Acrossocheilus zhangjiajiensis sp. nov., is described from the upper Lishui River Basin, a tributary of the Yangtze River, in Sangzhi County, Zhangjiajie City, Hunan Province, China. The description is based on an integrative taxonomic approach combining morphological examination, DNA barcoding, and mitogenomic analyses.

This new species is distinguished from all congeners by the following combination of characters: a maxillary barbel extending to the midline of the eye; a slightly hardened last unbranched dorsal-fin ray with a smooth posterior margin; dorsal-fin membranes with black stripes; the second primary vertical bar (PVB 2) positioned anterior to the origin of the dorsal fin; juveniles and adults possessing six distinct vertical black bars on the flank; and fewer than 40 lateral line scales.

Notably, it further differs from its sister species, A. jishouensis, in several morphometric traits, as well as the texture of the last unbranched dorsal-fin ray and the persistence of vertical flank bars throughout all life stages. The complete mitogenome of A. zhangjiajiensis sp. nov. is 16,592 bp in length. Phylogenetic analyses based on the mitochondrial COI gene and the 13 protein-coding genes (PCGs) support a sister-species relationship between A. zhangjiajiensis sp. nov. and A. jishouensis, with genetic distances of 3.1 % (COI) and 3.3 % (13 PCGs).

A COI-based haplotype network and species delimitation analyses further support the distinctiveness of the new species. This discovery increases the total number of valid Acrossocheilus species to 25 and provides critical data for the systematics, evolution, and conservation of this genus.