Abstract
The ciliate Euplotes encysticus Yonezawa, 1985 was insufficiently described so far regarding its living morphology, infraciliature and silverline system. Recently, a China population was isolated from brackish water (salinity 6 parts per thousand) near a coastal sandy beach (114 degrees 32'E 22 degrees 43'N) of the Daya Bay, South China Sea and subsequent investigations were performed on it in detail. Based on data available, the morphology of this species was summarized and a new diagnosis is given which is characterized by: medium-sized body with consistently 9 frontoventral, 2 caudal and 2 left marginal cirri; 30-40 adoral membranelles; 7 dorsal kineties; dorsal silverline system consisting of complex type with irregular network; capable of encystment. Both the morphology and SSr RNA gene sequence show, with high support, a close relationship of E. encysticus and Euplotes muscorum.