New Knowledge of Parasite Morphology

Abstract

Protozoan parasites which spend at least part of their life-cycle within their host’s cells are generally extremely small and have an organization that is beyond the limits of resolution of the light microscope. It was therefore only in the 1950s, with the advent of satisfactory techniques of electron microscopy, that it became possible to answer many of the important questions concerning the organisms of malaria. During the subsequent decade, the principal fine-structural features of the various stages of the life-cycles of several species of Plasmodium were established (see e.g. the reviews by Garnham, 1967; Ladda, 1969; Aikawa, 1971). Amongst other findings, it was finally settled that the blood forms are indeed intracellular and lie within vacuoles formed by the invagination of the red-cell membrane during merozoite invasion, that they feed phagocytically on the red-cell cytoplasm through a specialized cytostome, and that all invasive forms possess the characteristic “apical complexes” at their anterior end, formed by polar rings and attendant dense elongate vacuoles used during invasion of cells. © 1982 Oxford University Press.