Formation and role of malaria pigment.

Malaria pigment is most abundant and distinct in gametocytes. Trophozoites have variable amounts of pigment, depending on the species of Plasmodium and the stage of infection. In Plasmodium falciparum infection, blood smear preparations fall into two categories that are distinguishable at all levels of parasitemia; one type of preparation contains only pigment-deficient trophozoites, and the other type contains only pigment-rich trophozoites. Pigment accumulates in the residual body of the mature schizont and is lost upon rupture of the schizont. In contrast, pigment remains associated with the macrogametocyte and developing oocyst. Certain antimalarial drugs, such as chloroquine, have distinct effects on pigment clumping. These observations raise questions regarding the current idea of pigment as an inert excretory product of hemoglobin metabolism. It is suggested that pigment particles represent stacked utilizable intermediates of hemoglobin digestion that accumulate in the gametocyte to serve as a food reserve during the growth cycle in the mosquito.