Description of Paratrichodina yangtzeus sp. n. (Ciliophora: Trichodinidae) from the freshwater fishes in the Yangtze River, China.

Paratrichodina Lom, 1963 comprises more than ten species. Paratrichodina has been found so far in various freshwater, marine fishes and amphibians worldwide. This report provides the first record of Paratrichodina from freshwater fishes in China. Smears with trichodinids were air-dried and then the slides with trichodinid ciliates were impregnated with Klein dry silver impregnation technique in order to reveal details of the adhesive disc. All measurements are presented in micrometres and follow the system proposed by Lom. Detailed descriptions of the denticles are presented in accordance with the method proposed by Van As and Basson. Denticulate ring of the studied specimens is constituted by loosely arranged denticles and the adoral ciliary spiral is between 180 to 200 degrees. So the studied specimens were assigned to Paratrichodina. The presently described trichodinid resembles P. erectispina Lom et Haldar, 1977 and P. voikarensis Kashkovsky et Lom, 1979, but it is clearly distinguished from P. erectispina by the shape of denticle and some other measurements. Based on its unique characteristics, a new Paratrichodina species is erected, and named Paratrichodina yangtzeus sp. n.