The Effects of Cooling Conditions on the Behavior of Oxytricha bifaria (Ciliophora Hypotrichida)

The new analytic approach to the behavior of ciliates represented by the ethogram was used to study the locomotion of Oxytricha bifaria at different temperatures, isotropically applied according to a new protocol. It was shown that under these experimental conditions as the temperature dropped in stages from 24°C to 19°C to 14°C to 9°C, the general mobility of experimental populations decreased, as indicated by 1) the decreasing percentage of mobile organisms, 2) their decreasing velocity, 3) their prolonged backward creeping, and 4) the increasing length of their immobilization periods. The ethogram more particularly revealed that decreasing temperatures induced 1) the appearance of rightward arcs (several of them being travelled by specimens sliding on the substrate). 2) the reduction of both the radius and the velocity along the normal leftward arcs (A-) and the segments (S), and 3) the symmetric increase of both the central angle and the duration of the A- and S. These changes were reversibly induced: they disappeared when the temperature returned to 24°C. Moreover. a new behavioral pattern, the prolonged Side Stepping Reaction, was found. Helicoidal swimming, occurring only at 14°C, was analyzed. Among all of the behavioral parameters, nine were shown to change dramatically between 14°C and 9°C, demonstrating that the linear cooling of the populations induced clear non-linear effects.