Radiolarian. Coloured scanning electron micrograph (SEM) of the shell or test of a radiolarian. Radiolaria are single-celled protozoans that are found in marine plankton. This radiolarian has a spherical silicate skeleton with pores through which pseudopodia (false feet, not seen) of protoplasm project. As the animal floats in ocean currents the pseudopodia trap food particles on which the radiolarian feeds. Magnification: x350 when printed 10 centimetres wide. .