Vitamin E supplementation and intense selection increase clonal life span in Paramecium tetraurelia

Abstract

Vitamin E added to standard Cerophyl medium at 0.025 mg/ml significantly increased the mean clonal life span of 32 lines of Paramecium tetraurelia from 52.5 days and 187 fissions to 59.9 days and 209 fissions ( p < .05) when compared to unsupplemented, paired controls. The age-specific death rates increased exponentially. Regression analyses found a significantly lower rate of increasing mortality for the supplemented lines compared to controls. Weekly fission rates of supplemented lines declined linearly; more slowly than controls, but not significantly so. A second experiment tested two higher levels of supplemented vitamin E (0.10 and 1.00 mg/ml). Sublines receiving 1.00 mg/ml of supplemental vitamin E had higher rates of mortality and lower fission rates initially, but the mortality rates increased and the fission rates decreased more slowly than in sublines receiving 0.10 mg/ml supplemental vitamin E, resulting in maximum clonal life spans of 141 days and 330 fissions (1.00 mg/ml sublines), compared to 74 days and 271 fissions (0.10 mg/ml sublines). Survivorship of the last individual cells (nondividing) of each clone followed an exponential decline, with a significant increase in mean survival time for supplemented compared to unsupplemented cells ( p < .05).