FIGURE 1.

Kinetics of Plasmodium falciparum ookinete maturation in the mosquito bolus. Anopheles coluzzii mosquitoes were infected with P. falciparum gametocytes. Live parasites were isolated from a pool of 20 mosquito boluses and stained with anti-Pfs25 antibody at 11, 14, 17, 20, 23, and 36 h post infection (hpi). (A) Representative pictures of Pfs25-positive and Hoechst-stained ookinete stages as referred throughout this study (scale bar: 5 μm). Stage I: Round, indistinguishable from egressed female gamete. Stage II: Knob, small protuberance not exceeding in length the radius of the main spherical body. Stage III: Stem, elongated protuberance longer than the radius of the main spherical body. Stage IV: Enlarged stem, the elongated protuberance–still containing the nucleus–increasing in width. Stage V: Mature, terminally differentiated elongated form with or without residual spherical body; the nucleus has migrated from the residual spherical body to the stem. Ghost: elongated degenerated forms with non-continuous surface Pfs25 signal. (B) In vivo ookinete forms were classified as in (A). Proportion of ookinete stages out of total Pfs25-positive parasites is indicated for each time point. Every point represents the mean ± SEM of three independent experiments (N = 3, n = 200 parasites counted per time point). (C) Schematic representation of the duration of ookinete stages in the mosquito vector described in (A).