The dependence of reproductive rate on cell size and temperature in freshwater ciliated protozoa

Summary Reproductive rates have been calculated for ten species of ciliated protozoa in defined conditions. Interspecific double log regressions of generation time vs. cell volume have been computed at each of three temperatures (8.5° C, 15° C, and 20° C) indicating a significant dependence of reproductive rate on cell size. Recorded generation times varied from 6.38 h in Vorticella microstoma at 20° C to 1004 h in Spirostomum teres at 8.5° C. These values correspond to a range in r _m (day)^-1 of 2.607 to 0.017 and (day)^-1 of 13.554 to 1.017. The relationship between these data and similar published data for marine ciliates is examined and the value of such regressions in ecological studies of the protozoa is discussed.