Paramecia propel themselves by whiplash movements of their cilia, which are arranged in tightly spaced rows around the outside of their body. The beat of each cilium has two phases: a fast "effective stroke," during which the cilium is relatively stiff, followed by a slow "recovery stroke," during which the cilium curls loosely to one side and sweeps forward in a counter-clockwise fashion. The densely arrayed cilia move in a coordinated fashion, with waves of activity moving across the "ciliary carpet," creating an effect sometimes likened to that of the wind blowing across a field of grain.
[11]
The
Paramecium spirals through the water, as it progresses. When it happens to encounter an obstacle, the "effective stroke" of its cilia is reversed and the organism swims backward for a brief time, before resuming its forward progress. If it runs into the solid object again, it will repeat this process, until it can get past the object.
[12]
It has been calculated that a
Paramecium expends more than half of its energy in propelling itself through the water.
[13] Its method of locomotion has been found to be less than 1% efficient. This low percentage is, nevertheless, close to the maximum theoretical efficiency that can be achieved by an organism equipped with cilia as short as those of
Paramecium.
