Heterozygotes show an increase in mean life-span to 69 days (compared to 37 days for controls) at 25oC, an extension in mean life-span of 87%. Extension of 1% maximal life-span is greater than 45%. At 18oC, the increase in mean life-span in mutants approaches 100% and the increase in 1% maximum life-span approaches 50% compared to controls.