STUDIES ON THE PROTOZOAN FAUNA OF THREE-GORGE AREA IN CHANGJIANG (THE YANGTZE) RIVER

This study investigated the protozoan fauna of the Three-Gorge area in Changjiang River. Samples were collected at the section from Fengjie to Yichang in 1984, 1987 and 1988. 320 species of Protozoa consisting of 40 species of Mastigophora, 87 species of Sarcodina and 193 species of Ciliophora were identified, of which two are considered to be new species, i. e., Centropyxis complanata sp. nov. and Difflugia caudata sp. nov. Four new subspecies were identified: Difflugia urceolata eurystomas ssp. nov., Cemropyxis cass truncata ssp. nov., Trinema lincare oblongata ssp. nov. and Conochophthirus lamelidens medionucleus ssp. nov. Eightyseven species were new records in China. Comparison with the protozoan fauna of Tibet, some lakes in middle and lower reaches of Changjiang River, and Suoxiyu Natural Reserve, showed that most species of Protozoa can be found in all these areas and that their distributions are usually cosmopolitan. However, the dominant species may be different in different areas, owing to the differences in environmental features. Bodo, Centropyxis, Difflugia, Vorticella and Chilodonella are the dominant genera in terms of the number of species in the Three-Gorge area, and Cinetochilum margaticeum Perty, Chilodonella uncinata Ehrenberg, Cyclidium glaucoma Muller and Trochilia minuta (Roux) are the dominant species in terms of frequency of occurrence. The composition of Protozoa reflects the feature of subtropical zone, and these species are considered faunal elements of the oriental realm of the Three-Gorge area. Factors influencing the distribution of Protozoa were discussed. These factors include food, temperature, discharge, silt content etc. Among them, the current velocity is considered to be an important factor restricting protozoan distribution. Many species of Protozoa were found attached to filamentous algae inhabiting stagnant water rich in decomposing organic substances. The abundance of protozoan species at Yichang in the tributary Huangbaihe is probably related to the construction of Gezhouba dam which greatly reduced the current velocity.