A protozoan phylum, which includes the genera Nosema and Encephalitozoon, is characterized by the presence of unicellular spores with an imperforate wall and an extrusion apparatus having a polar tube and a polar cap; mitochondria are absent. They are intracellular parasites of invertebrates and lower vertebrates, with rare examples in higher vertebrates.
[micro- + G. sporos, seed]
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Examples: glitazone, GI cocktail, etc.