Video 4. Bull sperm cells swimming in a low-viscosity fluid (3 mPa·s) near the wall of a planar channel.

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DOI: 10.7554/eLife.02403.007

The video shows that, even at low viscosity, the flagellar beat of bull sperm is approximately planar. This follows from the fact that at certain instances the flagellum appears as a line (in contrast to human sperms at same viscosity, compare Video 2). Scale bar 20 μm.

DOI: http://dx.doi.org/10.7554/eLife.02403.007