Testing the Effects of DL-Alpha-Tocopherol Supplementation on Oxidative Damage, Total Antioxidant Protection and the Sex-Specific Responses of Reproductive Effort and Lifespan to Dietary Manipulation in Australian Field Crickets (Teleogryllus commodus)

Abstract

The oxidative stress theory predicts that the accumulation of oxidative damage causes aging. More generally, oxidative damage could be a cost of reproduction that reduces survival. Both of these hypotheses have mixed empirical support. To better understand the life-history consequences of oxidative damage, we fed male and female Australian field crickets (Teleogryllus commodus) four diets differing in their protein and carbohydrate content, which have sex-specific effects on reproductive effort and lifespan. We supplemented half of these crickets with the vitamin E isoform dl-alpha-tocopherol and measured the effects of nutrient intake on lifespan, reproduction, oxidative damage and antioxidant protection. We found a clear trade-off between reproductive effort and lifespan in females but not in males. In direct contrast to the oxidative stress theory, crickets fed diets that improved their lifespan had high levels of oxidative damage to proteins. Supplementation with dl-alpha-tocopherol did not significantly improve lifespan or reproductive effort. However, males fed diets that increased their reproductive investment experienced high oxidative damage to proteins. While this suggests that male reproductive effort could elevate oxidative damage, this was not associated with reduced male survival. Overall, these results provide little evidence that oxidative damage plays a central role in mediating life-history trade-offs in T. commodus.

Macronutrients and micronutrients drive trade‐offs between male pre‐ and postmating sexual traits

“…The angles between the linear vectors describe the relative differences in the performance between two traits with respect to the consumption of protein, carbohydrate and micronutrients. A smaller angle implies that the two traits tend to show similar expression in a similar location in the nutritional landscape, whereas a large angle would imply a conflict between the two traits during allocation of nutrients (Archer et al, ; Rapkin et al, ). With angles less than 40°, the optima for courtship song PC1, CHC PC1 and CHC PC2 resided close together in the nutritional landscape; Figure shows that the three traits were located in the region of high P:C ratio.…”

“…Although courtship song was found to be more metabolically expensive than calling song (Hack, ), the extended duration of calling song necessitates a greater amount of energy that would be provided by a high‐carbohydrate diet. Calling effort has previously been measured as the total time a male spent calling (Archer et al, ; Maklakov et al, ; Rapkin et al, ). In contrast, we assayed the temporal structure of the courtship song, finding song quality to be maximized by high‐P:C diets.…”

“…In comparison with macronutrients, the effect of micronutrients on life‐history traits has received relatively little attention within the Geometric Framework (Archer et al, ; Harrison et al, ). Moreover, unlike macronutrients, a specific micronutrient may influence a narrower range of targets; for example, Archer et al () found that vitamin E did not significantly improve life span in male T. commodus , yet this micronutrient was shown to balance the high oxidative stress in the testes of T. oceanicus , suggesting that the cost of oxidative stress may differ for life span and testes, and may result in differential effects of vitamin E on these two traits (L.W. Simmons, M. Lovegrove, S.J.…”

Dietary antioxidants, but not courtship effort, affect oxidative balance in the testes and muscles of crickets

“…Male crickets provided with greater access to nutritional resources have been shown to expend more energy on calling song than males with limited nutritional resources (Hunt et al, 2004), and the availability of protein in the diet has been found to underlie a resource allocation trade-off between calling song and lifespan in the congeneric cricket Teleogryllus commodus (Maklakov et al, 2008). Male T. commodus fed diets that stimulated increased energetic expenditure on calling song were found to have elevated levels of protein oxidation in whole-body lysates (Archer et al, 2015). However, dietary supplementation with vitamin E did not affect protein oxidation or antioxidant capacity (Archer et al, 2015).…”

“…Male T. commodus fed diets that stimulated increased energetic expenditure on calling song were found to have elevated levels of protein oxidation in whole-body lysates (Archer et al, 2015). However, dietary supplementation with vitamin E did not affect protein oxidation or antioxidant capacity (Archer et al, 2015).…”