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A large class of protozoans (phylum Apicomplexa, subkingdom Protozoa) consisting of obligatory parasites with simple spores lacking polar filaments; cilia and flagella are absent (except for microgametes, found in some groups), and locomotion is by undulation, gliding, or body flexion; sexuality, when present, is by syngamy, forming oocysts with infective sporozoites from sporogony. The class includes the gregarines and coccidia, the latter including many agents of human and animal disease, such as the plasmodia of malaria.
[Mod. L., fr. G. sporos, seed, + zōon, animal]