Figure 2: The residual body is a structure derived from a mother cell that contributes to the intravacuolar organization of parasites in rosettes. (A) Intravacuolar “rosette” micrographed after SEM-Tanaka processing. (B) Magnification of the area squared in (A) showing a link between the RB and the posterior ends of the proliferating tachyzoites (arrows). (C–E) micrographs obtained by thin sectioning. Arrows in (C–E) indicate membrane fusion between the RB limiting membrane and the tachyzoites membrane at the posterior end and the continuity between tachyzoites and the RB cytoplasm. (E) High magnification of the area squared in (D). Asterisks in (E) indicate accumulation of MNN at the periphery of the RB, and double arrows indicate parasites’ posterior polar ring. Insets in (C) represent the different types of membranes that limit the RB: a unit membrane (a) or a pellicle-like composed of three layers (b). Inset (c) in (C) indicates membrane fusion between the RB and the posterior end of a parasite. Ap: apical end of the tachyzoite; DG: dense granule; Gg: Golgi; m: mitochondria; N: nucleus; PVM: parasitophorous vacuole membrane; Po: posterior end of the tachyzoite; RB: residual body; Rh: rhoptries. μm; Bars in insets b and c = 500 nm.