Fig. 3

Plasmodium vivax sporozoites escaping from oocysts. a Low-power magnification of the external surface of the midgut showing protruding P. vivax oocysts (asterisks) of similar size. The rounded oocysts are arranged individually or in pairs protruding among muscle fibers (Mfb), trachea (Tra), and tracheoles (Tch) that rest on the external surface of the midgut. Magnification = ×200. b High-power magnification of a single sporozoite actively escaping by creating a hole (arrows) in the smooth oocyst (S-ooc) wall with its anterior end (asterisk). Note the rigid perpendicular shape of the escaping sporozoite (Spz). Magnification = ×8000. c and d Tens of grouped sporozoites (arrowheads) escaping from the lateral wall of an oocyst (S-ooc). Figure d is an enlarged image of the dashed area from figure c. Note the “rigid perpendicular shape” of the escaping sporozoites (Spz). Magnifications D = ×1400 and E = ×4000. e and f Free sporozoites (Spz) with the characteristic “comma-shape,” as seen in the mosquito hemocoel. Magnifications E = ×4100 and F = ×4300. g Empty oocyst (E-ooc) showing a hole through which the sporozoites escaped from the oocyst (asterisk). Magnification = ×1800. h Two side-by-side oocysts attached to the muscle fibers (Mfb) of the midgut. One smooth oocyst shows a completely stretched wall (S-ooc) and the other shows a flattened wall (F-ooc). Magnification = ×1300