Eimeria that infect fish are diverse and are related to, but distinct from, those that infect terrestrial vertebrates

► Fish are parasitized by a diverse assemblage of Eimeria parasites. ► These parasites are related to, but distinct from, Eimeriid parasites in terrestrial mammals. ► The Eimeria spp. in mammals, birds, and reptiles likely originated as parasites of fish. ► These parasites are related to free-living bacterophagous and photosynthetic alveolates.