oocyst
Quick Summary
An oocyst is a biological term referring to a zygote that is undergoing development, specifically within sporozoan parasites. These parasites, known as coccidia, are protozoans that inhabit the cells lining the intestines of vertebrates and invertebrates.12
The life cycle of coccidia involves two main phases: a free-living oocyst stage and a parasitic sporozoite stage. Oocysts are discharged by infected animals and represent the encapsulated zygote. Within the host, the parasite undergoes both sexual and asexual reproduction. Infection by coccidia leads to a disease called coccidiosis. Examples of genera within coccidia include Isospora, Eimeria, and Toxoplasma.2
It is important to distinguish oocysts from oospores, which are nonmobile spores produced by organisms in the phylum Oomycota, a group of fungus-like organisms.3
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