Long-term behavioral tracking of Paramecium bursaria

The ciliate protozoan <i>Paramecium</i> exhibits complex behaviors in response to environmental cues. Here we report a method that enables long-term observation (over 24 hours) of <i>Paramecium</i> with a simple experimental procedure. We observed the behavior of <i>Paramecium bursaria</i> , a species of <i>Paramecium</i> harboring symbiotic green algae, in gas-permeable chambers, where they exhibited light-dependent changes in behavior. We found that, in the 12-hour light-dark (LD) cycles, <i>P. bursaria</i> responds to both the dark-to-light and the light-to-dark transitions in different manners. This method provides a way to evaluate the long-term changes in the behaviors of <i>Paramecium</i> and other protists.