Spore forming protozoan

There are about 4000 species of protozoa that have spore forming stages in their life cycles. Most known species of spore forming protozoa belong to class Sporozoa and are parasitic. They lack cilia or flagella or pseudopodia and live within or between cells of their invertebrate or vertebrate hosts.

Figure: A lateral view  of  a generalized apicomplexan sporozoan. The apical complex components are shaded

They possess a complex of distinctive ring like tubular and filamentous organelles at the apical end visible only under the electron microscope. This phylum includes the gregarines which are extracellular parasites of insects, annelids and other worms and the coccidians that are intracellular parasites of blood cells of vertebrates and invertebrates: The most familiar coccidian is Plasmodium, the causative agent of malaria.