FIGURE 3.

Parallel time course highlights two limiting steps in in vitro ookinete development. The same preparation of Plasmodium falciparum gametocytes was diluted and fed to mosquitoes or induced to undergo gametogenesis in a parallel time course of in vivo versus in vitro development. Parasites were isolated from a pool of 20 mosquito boluses or collected from the in vitro culture and stained with anti-Pfs25 antibody at 8, 14, 17, 20, and 36 h after feeding or culture setup. Ookinete forms were classified as in Figure 2A, and the proportions of ookinete stages on total Pfs25-positive parasites in vivo (A) or in vitro (B) are indicated for each time point. Every point represents the mean ± SEM of three independent experiments (A: n = 200, B: n = 500 parasites counted per time point). Relative proportions of ookinete stages out of total Pfs25-posititve parasites excluding round forms (stages II to V and ghosts) per each time point are shown in vivo (C) and in vitro (D). Bar plots represent the mean proportions ± SEM of three independent experiments (C), n = 309, 439, 515, and 449 and (D), n = 91, 76, 114, and 63 Pfs25-positive parasites were analyzed per time point. The z-test was used to compare the mean proportion of each ookinete stage and its variances in vivo versus in vitro.