MORPHOLOGICAL REDESCRIPTION AND MOLECULAR DETERMINATION OF <italic>EUSTRONGYLIDES TUBIFEX</italic>, A NEWLY RECORDED NEMATODE SPECIES IN CHINA

This study aimed to identify the species of the larval Eustrongylides sp. nematodes parasitizing the intestine of Triplophysa microphthalmus in the Dacao Lake of Turpan area, Xinjiang, the adult Eustrongylides through experimental infection of domestic ducks. The parasites were identified based on morphological observation and molecular analysis of the internal transcribed spacer (ITS) sequence. The results indicated that the morphological characteristics of the obtained worms were consistent with Eustrongylides tubifex, including larger outer labial papillae compared to inner ones, raised margins on the male tail with smaller cuticular folds, and thick-walled eggs with multiple depressions. Molecular analysis of the 18S-ITS1-5.8S-ITS2-28S rDNA sequence (945 bp) revealed the highest similarity (97.39%) and the closest genetic distance (0.017) to Eustrongylides ignotus (GenBank: GQ215524). This study represents the first report of Eustrongylides tubifex in Triplophysa microphthalmus in China, which contributing to the understanding of the intermediate host range of Eustrongylides and providing fundamental data for the prevention and control of eustrongylidosis.