Taxonomic study on trichodinids parasitic on gills of freshwater fish, Carassius auratus from Chongqing, China, with the description of Trichodina brevicirra sp. nov.

Three trichodinid ectoparasites (Ciliophora: Peritrichida) were isolated from the freshwater fish, Carassius auratus collected from Chongqing, China. Trichodina brevicirra sp. nov. is described as a new one characterized by the short and slim ray. The other two trichodinids are Trichodina ngoma Van As & Basson, 1992 and Trichodina reticulata Hirschman & Partsch, 1955. T. ngoma Van As & Basson, 1992 is redescribed as a first record in Asia. Three populations of T. reticulata Hirschman & Partsch, 1955 fall within the range of morphometry and agree closely in the overall ap- pearance of the adhesive disc. Our observations suggest that denticle and central granules morphology may be more or less variable between and within populations, and that such minor differences should not be overestimated. It should be emphasized that there are 8 to 16 spherical or oval granules in central zone of adhesive disc.