Figure 6.

Functional implications of the Ca²⁺ drop. (A) Ca²⁺ signals derived from the data in Fig. 3 C. The amplitude of Ca²⁺ signals was rescaled to match the mean amplitude of single-cell Ca²⁺ signals. (B) Swimming paths reconstructed from Ca²⁺ signals in part A. Arrow indicates the swimming direction shortly before the second flash. (C) Sperm swimming in a gradient of resact. The UV profile used for uncaging resact is shown in shades of gray. At the foot and on the top of the gradient, the cell swims on smooth drifting circles (orange). In the region where the gradient is steep, the cell swims on looping trajectories (green). Arrows indicate the swimming direction.