HATLE, JD*; WELLS, SM; ALLEN, IC; FULLER, LE; MELNYK, S; QUATTROCHI , J; Univ. of North Florida: Calorie restriction enhances longevity without altering hemolymph protein or lipid storage in female grasshoppers

Calorie restriction (CR), under eating while avoiding malnutrition, modifies life history tactics in many organisms. Specifically, CR enhances longevity by allocating to storage and delaying fecundity. The hemolymph is a storage organ in many invertebrates, but its role in longevity via CR is poorly understood. We tested the effects of several diets on longevity of female lubber grasshoppers (Romalea microptera), which lay 2-3 clutches per lifetime. Hemolymph metabolites were tracked in individuals through adulthood. Constant CR (60% or 70% of ad libitum) and late-onset CR (started at 50 d, during the second clutch) increased longevity (Kaplan-Meier test, P=0.0002). Median adult ages at death in days were: ad libitum = 83; 60% = 135; 70% > 165; late-onset CR = 136. These diets did not delay the first clutch (P=0.142), reduce the mass of the first clutch (P=0.648), or reduce lifetime fecundity (P=0.275). Similarly, hemolymph lipid (all P>0.05) and glucose levels (all P>0.1) were not affected by diet. The level of total hemolymph proteins (70% of which is 3 hexamerins) also did not appear related to longevity. Total protein was transiently higher in the ad libitum group than all other diets, around the time of first oviposition. Because the late-onset CR group was still on an ad libitum diet, this result is unconvincing. More clearly, after the diet reduction in the late-onset CR group, hemolymph protein levels did not differ across diets (all P>0.17). Protein levels in the ad libitum group decreased at the first clutch and did not recover. Therefore, the enhanced longevity due to CR and late-onset CR does not appear to result from altered protein or lipid storage in the hemolymph.