Swimming Response of Individual Paramecia to Variable Forces

Experiments demonstrate that swimming paramecia exhibit a negative force-kinetic response. In particular, upward swimming paramecia exert a stronger propulsive force as they fight their tendency to sediment. This response is remarkable because it suggests that paramecia can sense forces as small as their apparent weight, which is less than 100 pN. We are investigating the origins of this response by applying variable magnetic forces to individual swimming paramecia and measuring how their swimming trajectories change. We conduct the experiments at the National High Magnetic Field Laboratory where it is possible to achieve forces sufficient to stall the swimmers. We will present our latest data on how paramecia adjust the geometry of their helical trajectories under varying forces.