NEW HOST RECORD AND STUDY ON POPULATION COMPARISON OF TRICHODINA NOBILLIS CHEN, 1963

Trichodina nobillis Chen, 1963 is an ectoparasitic ciliate for freshwater fishes, distinguished by its unique fan-shaped blade. While previously recorded from different hosts including fishes, amphibians, and crustaceans, it occurs predominantly on Cyprinidae fishes. The host named as Tinca tinca belonging to the Leuciscinae Cyprinidae of economic importance, has been poorly studied with regard to parasitic diseases, especially the Trichodiniasis. Although T. nobillis is a common and important pathogen in aquiculture, population-related research is extremely scarce. To explore intraspecific differentiation and phylogenetic relationships of T. nobillis, specimens were collected from the gills of cultured Tinca tinca in Yongchuan, Chongqing (CQ population) and Meishan, Sichuan (SC population). Based on the newly obtained morphological data and SSU rDNA sequences, we compared the population difference of T. nobillis and clarified its interspecific relationships with related species. Morphologically, the denticle morphology of adhesive disc was highly consistent between the two populations, but the SC population exhibited more developed denticles, whereas the CQ population lacked a distinct posterior projection. The quantitative analysis revealed significant differences (P