Similar to other heliozoans that are sometimes referred to as “sun animalcules,” Actinosphaerium species are radially symmetrical single-celled organisms. Also, their stiff pseudopodia extend in all directions and are composed of cytoplasm and intertwined helices of microtubules. The extensions are primarily used for capturing prey, which can then be incorporated into the body of the cell through a process known as phagocytosis.