Lipidic vacuoles in Plasmodium knowlesi erythrocytic schizonts

Electron microscopy of schizont development in erythrocytic Plasmodium knowlesi has revealed that spheroidal vacuoles 250 nm in diameter with semi-dense contents appear at the periphery of the parasite prior to the budding of merozoites. When treated with non-polar solvents, their contents are completely extracted, and after fixation in tannic-glutaraldehyde they contain regular lamellae with a periodicity of 5.5 nm. Both of these reactions are typical of lipids. Some of these structures are associated with phagosomal vacuoles which may contribute to their lamellae. They disappear at the onset of merozoite formation, but membranous whorls of various sizes continue to be associated with the schizont surface during budding of merozoites. It is suggested that the lipidic vacuoles are a source of preformed lipid which can be utilized rapidly during the generation of merozoites.