Paramecium protozoan. Light micrograph of a IParamecium sp. i ciliate protozoan. This single- celled organism is covered in numerous cilia (microscopic hairs) that it uses for locomotion and to waft food particles into its mouth. IParamecium sp. i protozoa inhabit fresh water, and feed mainly on bacteria and smaller protozoa. When some IParamecium sp. i feed on photosynthetic cells (green spheres) instead of digesting them they incorporate them into their own cell and use them to produce energy from sunlight. The process of incorporating other cells is called endosymbiosis. IParamecium i cells vary in length between 35 microns and 150 microns.