Bulbous membrane invagination structures (bulins) in the mitochondrion. (A) 3D rendering of the mitochondrion in a mid-segmentation schizont with a thin (blue arrow) and thick (red arrow) part. (B) Fluorescent microscopy of mito-mScarlet showing bulbous mitochondrial parts at the base of a mitochondrial branch. Scale bars, 2 μm. (C) Micrograph image of mid-segmentation schizont showing four bulins. Scale bar 1 μm. (D) Micrograph images of mitochondrial bulins in different schizont stages. (E) micrograph images of apicoplast bulins (yellow arrows) in early stage schizont. (D and E) Scale bars, 0.5 μm. (F) 3D rendering of the mitochondrion (gray, 7% opacity) and membrane invaginations (blue). Red arrows indicate bulins at the base of a mitochondrial branch just outside the forming merozoite entrance. Orange arrows indicate membrane invaginations at a branching point in the mitochondrial network. Green arrows indicate membrane invaginations in the middle of a continuous mitochondrial branch. The number between brackets indicate schizont ID number (Table S3).