Vanmanenia marmorata, a new species of loach (Teleostei: Gastromyzontidae) from the middle Chang-Jiang Basin in Guizhou Province, south China

Abstract

The gastromyzontid genus Vanmanenia was established by Hora in 1932, based on the type species Vanmanenia stenosoma. The genus is a loach group adapted to running waters of streams from southern China, northern Vietnam and Laos. Currently, 19 valid species of the genus have been recognised. The northernmost distribution of the genus is the Yangtze River (= Chang-Jiang in Chinese) Basin and five species (V. maculata, V. intermedia, V. stenosoma, V. pseudostriata and V. gymnetrus) have been reported from the Basin. Vanmanenia marmorata, a new hillstream species of loach, is here described from the middle Chang-Jiang Basin in Guizhou Province, south China. It is distinguished from its congeners by having a combination of the following characters: three triangular-shaped rostral lobules; postdorsal saddles wider than interspaces; a more backwards-placed anus (the vent to anal distance 30.5–36.9% of the pelvic to anal distance); a larger gill opening with its upper extremity reaching the level of the middle of the orbit; anal-fin base length 5.6–6.4% of SL; caudal-peduncle length 11.6–12.9% of SL; prepelvic length 51.1–53.4% of SL. Its validity is also affirmed by its distinct cyt b gene sequence divergence with all sampled congeners and its monophyly recovered in a cyt b gene-based phylogenetic analysis.