LIFE-SPAN SHORTENING OF THE NEMATODE CAENORHABDITIS-ELEGANS UNDER HIGHER CONCENTRATIONS OF OXYGEN

The effects of higher concentrations of atmospheric oxygen on the lifespans of wild type and a temperature-sensitive zyg-9(b244) mutant of the nematode Caenorhabditis elegans were examined. Their mean and maximum lifespans decreased with increasign oxygen concentration. The mean and maximum lifespans of the wild type under 60, 75, and 90% oxygen shrunk by 17 and 10, 31 and 31, and 40 and 41%, respectively, as compared with those under 21% oxygen (normal air). The mean and maximum lifespan of the zyg-9(b244) mutant under 60 and 90% oxygen shrunk by 18 and 22%, and 38 and 39%, respectively, as compared with those under 21% oxygen. The Gompertz analysis of the survival data of the wild type revealed that the exponential Gompertz component, the rate of acceleration of mortality, increased with increasing oxygen concentration: i.e. the ageing was accelerated under higher concentrations of oxygen. Oxygen acts as a lifespan determinant of the nematode. When the animals were exposed to a high concentration of oxygen at the early phase of lifespan, the oxygen-induced lifespan shortening was not observed. This means that oxygen-induced damage leading to lifespan shortening is repaired under 21% oxygen and that the oxygen-induced lifespan shortening does not result from any alteration in development and/or mutation.