FIM-SEM imaging of CC membranous carriers. (A–D) Four representative block face FIM-SEM images reveal the membranous structures contained within the rod CC. Note that the density of the vesicle tubules was variable in different sectional views. In the CC sections that are less crowded, individual vesicles with clear membrane profiles were readily detectable in both inner and outer shafts (black arrows). White arrows point to the vesicle clusters of various sizes. Scale bar = 150 nm (E) A block face FIM-SEM image shows that the membrane structures sharing similar morphological features to those expressed in the CC are also abundantly expressed in the basal rod OS axoneme (Ax). Some of these vesicular membranes were immediately adjacent to the disc membranes as if they are about to fuse (white arrows point to examples). Scale bar = 300 nm.