Apicomplexans
Nearly all apicomplexans are parasites of animals, and some cause serious human diseases. The parasites spread through their host as tiny infections cells and sporozites. Apicomplexans are so named because one end (the apex) of the sporoplexans cell contains a complex of organelles specialized for penetrating host cells and tissues. Although apicomplexans are not photosynthetic, recent data show that they retain a modified plastid (apicoplast), most likely of red algal origin.