Aging, Life Span, and Energetics under Adult Dietary Restriction in Lepidoptera

Abstract

Stressful conditions can affect resource allocation among different life-history traits. The effect of dietary restriction (DR) on longevity and reproduction has been studied in many species, but we know little about its effects on energetics, especially in flying animals that have high energy demand. We assessed the effects of DR on metabolic rate throughout the entire adult life span in two butterfly species, Colias eurytheme and Speyeria mormonia. We cut the food intake of adult females in half and measured resting metabolic rate (RMR) and flight metabolic rate (FMR) together with body mass repeatedly throughout life. In both species, DR reduced body mass, but mass-corrected FMR was not affected, indicating that flight capacity was retained. DR lowered RMR and reduced fecundity but had no effect on life span. FMR declined with age, but the rate of senescence was not affected by DR. In contrast, aging had a strong negative effect on RMR only in control females, whereas food-restricted females had more stable RMR throughout their lives. The results suggest that flight capacity is conserved during nutritional stress but that investment in flight and survival may negatively affect other important physiological processes when resources are limited.

Nectar resource limitation affects butterfly flight performance and metabolism differently in intensive and extensive agricultural landscapes

“…EL butterflies reduced their RMR under food stress, which would save energy that could be subsequently used for reproduction. Food stress reduced RMR in a few other flying insects [5,25]. Butterflies used in our experiments were wild-caught, young adults, which all had briefly experienced nectar conditions in the landscape of origin.…”

“…Income breeders rely on nectar consumption (or alternative feeding resources). Nectar intake positively affects life-history traits in several species [5,6]. Nectar is composed of water and sugars (mainly sucrose, fructose and glucose), and also amino acids [7].…”

Effects of Increased Flight on the Energetics and Life History of the Butterfly Speyeria mormonia

“…For example, chronic caloric restriction reduces fecundity in many animals while lifespan is prolonged [ 11 ]. In our study organism, the butterfly Speyeria mormonia (Nymphalidae), lifespan is not affected by adult food restriction but reproductive output depends on adult feeding [ 12 , 13 ]. Here we examine the effects of a pulling force on the network, through increased flight.…”

Old male sex: large ejaculate, many sperm, but few offspring

“…However, we also found that oxidative damage decreased with age. This suggests that older butterflies have reduced their production of ROS compared with younger ones, for instance by reducing metabolic rate as observed in other Lepidoptera (Niitepõld and Hanski 2013;Niitepõld et al 2014). Antioxidant defences were found to increase while oxidative damage tended to decrease with mating frequency.…”