Retained maternal cytoskeleton is contained in membrane of the residual body. (A) Correlated fluorescence (GFP-tub; inset scale bar, 5 μm) and transmission electron microscopy of Δcsar1-infected fibroblasts. Boxed regions are zoomed in the indicated panels. (B and C) Structures consistent with parasite microtubule cytoskeleton are found within the residual body. (B′ and B″) serial slices of the region in B show multiple retained conoids are tightly packed within the residual body. (D) Cross-section of a bundle of 20 subpellicular microtubules delineated by the residual body membrane. BC—basal complex; Cn—conoid; spMT—subpellicular microtubules; white arrowheads—parasitophorous vacuolar membrane; orange arrowheads—residual body membrane; Host Mito—host mitochondria. Images are representative of n = 4 vacuoles imaged by TEM.