Fig. 3. (A) Averaged (n=10) vector plots based on particle motions recorded after valve opening at the times indicated. The orientation of the laser sheet was orthogonal to the propagation direction of the stimulus (z–y plane in Fig. 1A). The distance between the pipette and the laser sheet was adjusted to 5 cm. Scaling vectors (large horizontal arrows) represent 12.5 cm s^-1. For better visualization, the vectors are enlarged in the first three images. For parallel pressure measurements, a hydrophone was placed 5 cm away from the pipette tip. (B) Mean changes in hydrodynamic pressure (n=10) caused by the vortex ring. Inset: pressure changes, measured 100–400 ms after valve opening, at an expanded time scale. (C) Mean water velocity (n=10) measured with an anemometer. In B and C, zero indicates the time of valve opening. Gray shaded areas in B and C represent ±1 s.d.