Figure 2.

Survivorship, metabolic rate, and metabolic output of wild-type C. elegans and long-lived C. elegans mutants. (a) Survivorship of wild-type (n = 168), age-1 (n = 202), daf-2 (n = 167), and clk-1 daf-2 worms (n = 106) maintained at 20°C. (b) Metabolic rate of wild-type and long-lived worms. Metabolic rate was measured over a 9-day period with worms maintained at 20°C. Worms from each strain were measured when 3, 6, 9, and 12 days old. The double age-1 fer 15 mutant was used in all of these experiments. Each bar represents the mean (± SEM) of six separate measurements with 50 worms used per sample measurement. The metabolic rate of daf-2 and clk-1 daf-2 worms is significantly less than wild-type worms at every time point (P < 0.02, Mann–Whitney U test). (c) Metabolic output of wild-type and long-lived worms over a 12-day period. Metabolic output was calculated by integrating the area under a plot of metabolic rate for 9 days. Each bar represents the mean (± SEM) of four integration values. Metabolic output of daf-2 and clk-1 daf-2 is significantly less than wild type (P < 0.01; unpaired Student’s t test). Although reduced, the metabolic output of age-1 was not significantly less than wild type (P = 0.09). Further experiments showed that, despite its longer life span, the lifetime metabolic output of age-1 is not significantly different from that of wild type (data not shown). (d) Metabolic rate comparison between wild-type, daf-2, and clk-1 daf-2 worms when worms are at equivalent body size and development. Each bar plots the mean (± SEM) of two measurements.