Experimental design. Liquid-hatched L1 stage C. elegans were exposed to 7.5 J/m2 UVC over 48 h, in the absence of food, permitting nDNA repair but accumulation of mtDNA damage . Nematodes were then placed on food plates and followed for another 48 h. We measured mRNA levels, genome copy number, DNA damage, ATP levels, and oxygen consumption at multiple times during and after the UVC exposures. All times are given relative to the final dose and transferral to food (= “0 h”). For example, mRNA sampled immediately prior to the second dose of UVC would be described as sampled at “-25 h”, and “3 h” if it were sampled 3 h after the final UVC exposure. Representative examples are presented to orient the reader.