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an order of one-celled animals of the class Sporozoa. There are approximately 1,000 species. They are intracellular parasites of the epithelial tissue primarily of the digestive organs of invertebrates (annelid worms, mollusks, and arthropods) and vertebrates. They look like small rounded cells with a bubble-shaped nucleus.
Almost every species of Coccidia parasitizes only one definite species of animal host. Most Coccidia exhibit regular alternation of asexual reproduction (schizogony), a sexual process, and sporogony. Asexual reproduction is absent only in the most primitive group—Protococcidiida (genus Eucoccidium). Spores keep the sporozoites viable outside the host’s body for several months, until the oocyst is swallowed by the animal host. The majority of species of Coccidia develop in one host. Some Coccidia have two—for example, members of the genus Aggregata undergo asexual reproduction (schizogony) in crabs and the sexual process and sporogony in gastropod mollusks. Coccidia are very widely distributed. Some cause coccidiosis.
REFERENCEKheisin, E. M. Zhiznennye tsikly koktsidii domashnikh zhivotnykh. Leningrad, 1967.
V. A. DOGEL’