Video
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The video is five joined sequences that correspond to Figures 1, 2, 3, 5, and 6. Frame rate and time in milliseconds is to the right of each videoframe.
The first sequence shows a whole pluteus at low magnification. An algal cell changes direction at the upstream side of the ciliary band on an arm as it is initially caught and then several times again as it is moved along the arm toward the mouth. The subsequent sequences show these captures at the band at higher magnification in two different views.
The second and third sequences are optical sections through the band, with ciliary beat in the plane of focus. In each sequence a ciliary reversal retains an algal cell that has entered the area swept by effective strokes of cilia. The curvature of recovery strokes indicates forward and reversed beat of cilia.
In the fourth and fifth sequences, the ciliary band is in the plane of focus and cilia beat through the plane of focus. Changes in ciliary beat are initiated when and where an algal cell is retained. The change in effective strokes indicates that the extent of changed ciliary beat during a capture is much larger than the captured particle but a small part of the ciliary band.
In combination, the sequences show that particles are captured by a brief reversal of beat of a small part of the ciliary band, which indicates a small and brief reversal of the feeding-swimming current. The volume of the diverted water is much smaller than the volume of the feeding current (hence the concentration of food) but much larger than the captured particle.
