The fine structure of the developmental stages of the microsporidian Nosema apis Zander

Schizonts, sporonts and sporoblasts of Nosema apis from honey bees collected in the summer and winter were studied with the electron microscope. The nuclei usually had a diplokaryon arrangement. Intranuclear spindles with polar vesicles were associated with division. Schizonts had a single limiting unit membrane, whereas sporonts had a two-layered wall. Sporonts from summer bees had only a thin single limiting membrane in some areas and evidence of endocytosis was sometimes seen in these. Sporonts from winter bees had branched tubular outpocketings from the wall. In sporoblasts, the development of the polar filament was closely associated with a network of dense structures interwoven with a system of tubules evidently of ER derivation; the Golgi complex was associated with this network.