Life History Features and Aging Rates: Insights from Intra-specific Patterns in the Cricket Acheta domesticus

We carried out 42 lifetime studies of male and female crickets (Acheta domesticus) treated with different diets, nutritional supplements and dietary restriction (84 groups). Maximal longevity of controls averaged ~118 days and various treatments obtained lifespans of 86–257 days. Overall, greater longevity was most strongly associated with slower growth and delayed maturation. Early nymphal mortality and early fasting stress were also associated with life extension. The opposite associations of growth rate and stress resistance with maximal life span are consistent with modulation of aging by the target of rapamycin (growth) and forkhead transcription factors (stress resistance). Unlike inter-specific comparisons or intra-specific comparisons of species differentiated into strains or breeds, body size did not emerge as a strong predictor of cricket longevity. Rather, targeted body size was strongly compensated for in crickets whereas most genetically differentiated breeds of mice, rats, horses and dogs express breed-specific sizes and growth rates. Both extension of the juvenile period and adult lifetime contributed to increases in maximal longevity of crickets, although for extreme life extension, extended immaturity was a greater factor than adult life span. We discuss the inter- and intra-specific allometry of life histories from a perspective of aging and suggest that inter-specific variance may particularly reflect exogenous mortality risks whereas intra-specific aging is dominated by constraints on productivity.