Figure 1.

Dark-field images of M. pusilla, a small alga that swims using an unusual flagellum with a very short 9 + 2 region and a long extension of the central pair microtubules. These movies were originally taken on 16-mm film using dark-field optics. The negatives were converted to video format; thus the cell appears dark against a light background. (A) Movie 1 shows a free-swimming M. pusilla being propelled by a rotating helical central pair of microtubules (∼600-kb QuickTime movie). (B) Movie 2 shows a M. pusilla stuck by its flagellum and the cell body rotating (∼1-Mb QuickTime movie).