Factors Controlling the Length of Autogamy-Immaturity in Paramecium tetraurelia

Abstract

Autogamy-immaturity is the period during which autogamy can not be induced by natural starvation; in Paramecium tetraurelia, autogamy first becomes induceable at about 7 fissions after the previous autogamy, and thereafter the percent of cells undergoing autogamy increases gradually to almost 100% at the clonal age of about 20 fissions and remains at 100% thereafter. The length of autogamy-immaturity (LAI), determined by plotting the percent of cells in autogamy versus the number of fissions, was found to be similar in two cultures grown at different fission rates at 25°C and 30°C. This indicates that paramecia count LAI by the number of fissions, not by the calendar time. LAI estimated from the peaks of percent autogamy through successive autogamous generations was also similar in two continuous cultures grown with different cycles of growth and starvation at 25°C and 30°C, indicating stability of LAI under ordinary laboratory conditions. However, LAI was affected by the cultural age of paramecia from which the new autogamous generation was derived: advanced cultural age shortened the LAI in the following generation.