The karyotype of Plasmodium falciparum determined by ultrastructural serial sectioning and 3D reconstruction

The karyotype of the erythrocytic stages of Plasmodium falciparum was determined to be 14 by counting the number of kinetochores in the mitotic spindle of young schizonts. Fourteen pairs of kinetochores were identified in 3-dimensional reconstructions of the spindle derived from serial longitudinal and transverse sections. Kinetochores were ovoid (45 X 25 nm) in transverse sections, measured 100 nm in longitudinal section, and were heptalaminate in structure. A pair of spindle microtubules passed through each kinetochore. In schizonts at anaphase, each pole of the mitotic spindle consisted of paired kinetic centers inserted on the nuclear membrane. The kinetic centers resembled nuclear pores, but were more electron dense and were associated with spherical masses of an electron-dense cytoplasmic material.