Morphologic Differentiation and Taxonomic Status of Pseudecheneis (Siluriformes: Sisoridae) from Irrawaddy and Salween Drainages, China

One hundred and fifteen specimens of Pseudecheneis from the Irrawaddy and Salween drainages were divided into ten groups according to localities. When analyzed by the methods of multivariate morphometrics, twenty-five frame and 14 general characteristics were measured. According to the results of principal components analyzed twice, specimens clustered together by scatter plots of scores were gradually picked up and could be divided into five types. The first type only occurred in the middle and lower Longchuan Jiang, a branch of Irrawaddy. It is distinguished from other types by its slender and elongated caudal peduncle and can be identified as P. stenura. The other four types were un-described species. The second type was distributed in the upper Longchuan Jiang, a branch of the Irrawaddy and they had an extremely elongated body. The third type appears in the Wandian He, a branch of the Salween. And the length of its pectoral fin was longer than others which was the main distinguishing characteristic from the other types. Combined with the anatomical and phylogenic results and molecular biological studies, this type is considered an un-described species. The fourth and fifth types occur respectively in the Nanding He, a branch of the Salween and the Daying Jiang, a branch of the Irrawaddy. They differ from each other by the color pattern on the dorsal surface. Furthermore, some specimens from Qushi of Tengchong County and specimens from the Daying Jiang are not differentiated by morphometrics or external characteristics. They belong to a different geographic population of the same species. Different species, or specimens from Qushi of Tengchong County can be considered a new species. All suppositions should be confirmed by further studies in the future.