Exogenous oxidative stressors elicit differing age and sex effects in Tigriopus californicus

As organisms age, cellular function declines in a time-dependent manner. Oxidative stress induced by reactive oxygen species damages cellular machinery and contributes to senescence which narrows the homeostatic window needed to maintain function and survive stress. Sex differences in longevity are apparent in many species and may be related to sex-specific homeostatic responses. Here we use the emerging aging model system Tigriopus californicus, the splashpool copepod, to estimate sex- and age-specific tolerances to two chemical oxidants, hydrogen peroxide and paraquat. Sex-specific tolerance was estimated for both oxidants simultaneously for 15 age-classes. As animals aged, hydrogen peroxide tolerance decreased but paraquat tolerance increased. Also, we observed no sex difference for hydrogen peroxide tolerance, while females were more tolerant of paraquat. Our results demonstrate that oxidative stressors can have dramatically different sex and age effects in Tigriopus californicus. These findings underscore the challenges ahead in understanding relationships among oxidative stressors, sex, and aging.