IFT trains of similar length are distributed on doublets 3–4 and 7–8. (A) Successive images from Video 1 showing WT trypanosomes analyzed by FIB-SEM. Each image corresponds with a Z stack of three slices between positions 424 and 475. The progression is from anterior to posterior. Top: Low magnification of the cell body with major organelles indicated. F, flagellum; G, glycosome; M, mitochondrion. Bottom: A magnification of the flagellum area is shown with the axoneme (A) and the PFR. The arrows indicate IFT particles. (B) Portions of flagella reconstructed after FIB-SEM. Each axoneme is shown with a different color, and IFT trains are in red (for animation, see Video 2). (C) Another example of a flagellum from a WT trypanosome coming from a different stack than the one presented in A and B with the axoneme (sky blue) and several IFT trains (red). Doublet numbers and flagellum orientation (basal body and tip) are indicated. (D) Length of the IFT trains on doublets 3–4 (green; n = 52) and 7–8 (magenta; n = 56) determined from FIB-SEM analysis. Data are from 27 portions of flagella representing a total axoneme length of 166 µm. Two populations can be separated with short trains (green) and longer ones (magenta; see text for details).