Velocity and Graviresponses in Paramecium during Adaptation and Varied Oxygen Concentrations

Abstract

Summary Populations of Paramecium caudatum adapted to new O 2- and chemical environments within at least 6 hours show two subgroups of cells which are distinguished by their median swimming velocity. “Fast swimmers” prevailed at the beginning, and “normal swimmers” toward the end of the adaptation period. The median swimming rate of these two groups was largely constant throughout 6 hours, apart from initial disturbances following transfer into a closed environment. The degree of air saturation of the experimental solution (5% to 100%) was monitored continuously in a new flow-through chamber. Changes in the O 2 level did not have a consistent effect on the swimming velocity. Negative gravitactic orientation in normal swimmers gradually decreased with incubation time. Gravitaxis was absent in the fast swimmers. Variation in O 2 tension did not produce perceptible effects on gravitaxis. At all air saturations and incubation times negative gravikinesis was found, both in normal and in fast swimmers, centering near −40 µm/s. Gravikinesis correlated with swimming velocity, but not with O 2 tension. No correlation was found between the kinesis and orientation coefficients. The data suggest that gravikinesis in Paramecium is largely independent of O 2 levels and adaptation time. Graviorientation declines with adaptation, but is not a direct function of O 2 saturation of the medium.