Loaches of Vanmanenia (Cypriniformes: Gastromyzontidae) from Yunnan, China with Description of a New Species.

Abstract

After comparing specimens of Vanmanenia collected from the Lancang-jiang (the upper Mekong River), Yuan-jiang (the upper Red River), Lixian-jiang (first branch of the Red River), and Jinsha-jiang (the upper Yangtze River) drainages in Yunnan, China, we considered the specimens of Vanmanenia from Shunbi Township, Yangbi County, Yunnan (a branch of the Lancang-jiang drainage basin, the upper Mekong River) a new species, herein named V. microcephala sp. nov. Our investigation also suggested that V. striata should be restored as a valid species. On the basis of the systematic comparison of morphological characteristics of the genus Vanmanenia and based on the combination of the characteristics of the rostral fold, rostral barbels, the bars/marks on the flank, the rows of spots on the paired fins, and the markings on the caudal-fin base, the loaches of Vanmanenia should be divided into three groups: 1) the barred group, characterized by bars on the flank, 2), the cusped rostral fold group, characterized by the rostral fold lobes forming a cusp process, and 3) the barbeled rostral fold group, characterized by the rostral fold lobes specialized as secondary barbels. The barred group differs from congeners in Vanmanenia by the following combination of characters: three rostral lobes with a smooth and arcuate outer edge, a pattern of bars on the flank, and spotless paired fins. This group includes six species: V. crassicauda, V. microcephala sp. nov., V. serrilineata, V. striata, V. tetraloba, and Vanmanenia pseudostriata. The new species, V. microcephala, differs from the other species in the barred group by the following combination of characters: the lateral side of the body with 14-22 vermiculations with widths smaller than the diameter of the eye; the dorsal side of the head covered with a large black blotch; the gill opening smaller and its upper angle aligned with the lower edge of the eye; and the head smaller, head depth 45.2-47.1% head length. The characteristic evolutionary trends, origin, and taxonomic status of the barred group in the genus Vanmanenia are also discussed.