P. falciparum undergoes continuous change during its life cycle. It begins as a spindle-shaped sporozoite that is 10–15 μm long. In the liver, it grows into an ovoid schizont of 30–70 μm in diameter. Each schizont produces merozoites, approximately 1.5 μm long and 1 μm in diameter. Meanwhile, the merozoite forms a ring-like structure in the erythrocyte and becomes a trophozoite. The trophozoite feeds on hemoglobin and forms a granular pigment called hemozoin.
The two images on the right show P. falciparum ring-like structures. The top image shows a thick smear, while the bottom shows a thin one.
A unique feature of P. falciparum is that the gametocytes are elongated and crescent-shaped (image below). A mature gametocyte measures 8–12 μm long and 3–6 μm wide. The ookinete, a form found in the mosquito, is also elongated and measures roughly 18–24 μm. The oocyte is rounded and can grow up to 80 μm in diameter. The ookinete and oocyte are mosquito forms and are thus not seen in the blood.
CDC. (2024). CDC - DPDx - Malaria
