**Figure 2.** **Variation in COX1 decreases mitochondrial mass with age.** All measured mitochondrial indicators were normalized to the value of day 0 N2 worms. (**A**) Level variation of OCR with age. (**B**) Level variation of mtDNA with age. (**C**) Level variation of ROS with age. (**D**) ATP level variation with age. Data shown as the means ± SEM. Statistical analysis was performed by using two-tailed unequal variant Student’s t-test (* P-value < 0.05, ** P-value < 0.01).