Genetic, behavioral and environmental determinants of male longevity in Caenorhabditis elegans

Males of the nematode Caenorhabditis elegans are shorter lived than hermaph rodites when maintained in single-sex groups. We observed that groups of yo ung males form clumps and that solitary males live longer, indicating that male-male interactions reduce life span. By contrast, grouped or isolated h ermaphrodites exhibited the same longevity. In one wild isolate of C. elega ns, AB2, there was evidence of copulation between males. Nine uncoordinated (unc) mutations were used to block clumping behavior. These mutations had little effect on hermaphrodite life span in most cases, yet many increased male longevity even beyond that of solitary wild-type males. In one case, t he neuronal function mutant unc64(e246), hermaphrodite life span was also i ncreased by up to 60%. The longevity of unc-4(e120), unc-13(e51), and unc-3 2(e189) males exceeded that of hermaphrodites by 70-120%. This difference a ppears to reflect a difference in sex-specific life span potential revealed in the absence of male behavior that is detrimental to survival. The great er longevity of males appears not to be affected by daf-2, but is influence d by daf-16. In the absence of male-male interactions, median (but not maxi mum) male life span was variable. This variability was reduced when dead ba cteria were used as food, Maintenance on dead bacteria extended both male a nd hermaphrodite longevity.