Protozoan ingesting rotifer. Phase contrast light micrograph of an Actinosphaerium sp. heliozoa protozoan, showing rotifers (centre) that it has ingested. This single-celled freshwater organism has many pseudopodia radiating outwards from its cell body that are used for capturing prey. A peripheral layer of large vacuoles assist in floatation. Rotifers are microscopic aquatic animals that are related to roundworms. Magnification: x200 when printed at 10 centimetres wide.