Movie S4.

Frequency of muscle contraction dictates the speed of symmetrization. The movies are in real time. Part 1: Tetramer swimming in seawater. Part 2: Tetramer swimming in seawater with reduced MgCl2 (50% of the concentration in normal seawater). Part 3: Tetramer swimming in seawater with 80 μM menthol. The movie can also be viewed through the following YouTube link: www.youtube.com/watch?v=DxrNW0qcWy4&feature=youtu.be.