Position-dependent onset of spindle oscillation. (A and B) On the left, drawing of a one-cell stage C. briggsae embryo. Nuclei are shown in gray, microtubules in light green, the anterior centrosome in green, and the posterior centrosome in red. The broken line represents the cell center. On the right, the position of the posterior centrosome along the A/P axis (black curve) and the transverse movements of both centrosomes (green and red curves) are shown relative to cytokinesis onset (t = 0 s). One representative embryo is shown, among the 9 intact embryos (A) and 12 embryos in which the anterior astral microtubules have been severed (B) that were analyzed. (C–E) From cut and intact embryos, measures of the position of the posterior centrosome at oscillation onset (C), oscillation duration in seconds (D), and maximum amplitude of posterior centrosome oscillations (E) are shown relative to the time at oscillation onset (in seconds to cytokinesis onset).