Life Cycles of Two Isospora Species in the Canary, Serinus canarius Linnaeus*

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Abstract
The endogenous stages of I. serini Aragao and I. canaria Box are described from experimentally infected canaries, S. canarius Linnaeus. Unlike other Coccidia, the 1st part of the I. serini life cycle takes place in mononuclear phagocytes. Five asexual generations are described from this cell type; 2 additional asexual generations and the sexual stages take place in the intestinal epithelium. I. canaria has a conventional coccidian life cycle in that all of the endogenous stages are in the epithelium of the small intestine, with 3 asexual generations and the sexual generation described in the duodenal epithelium. The 2 spp. differ in their position relative to the nucleus of the intestinal epithelial cell. I. serini is usually on the lumenal side of the nucleus while I. canaria is below the nucleus, toward the basement membrane. The prepatent period is 4-5 days for I. canaria and 9-10 days for I. serini. Patency lasts for 11-13 days in I. canaria infections, but duration of oocyst output is more chronic in I. serini infections, persisting for as long as 231 days. Both species have a diurnal periodicity of oocyst discharge which occurs in late afternoon and evening.