Learning to starve: impacts of food limitation beyond the stress period

Abstract

Starvation is common among wild animal populations, and many individuals experience repeated bouts of starvation over the course of their lives. Although much information has been gained through laboratory studies of acute starvation, little is known about how starvation affects an animal once food is again available (i.e. during the refeeding and recovery phases). Many animals exhibit a curious phenomenon - some seem to 'get better' at starving following exposure to one or more starvation events - by this we mean that they exhibit potentially adaptive responses, including reduced rates of mass loss, reduced metabolic rates, and lower costs of digestion. During subsequent refeedings they may also exhibit improved digestive efficiency and more rapid mass gain. Importantly, these responses can last until the next starvation bout or even be inherited and expressed in the subsequent generation. Currently, however, little is known about the molecular regulation and physiological mechanisms underlying these changes. Here, we identify areas of research that can fill in the most pressing knowledge gaps. In particular, we highlight how recently refined techniques (e.g. stable isotope tracers, quantitative magnetic resonance and thermal measurement) as well as next-generation sequencing approaches (e.g. RNA-seq, proteomics and holobiome sequencing) can address specific starvation-focused questions. We also describe outstanding unknowns ripe for future research regarding the timing and severity of starvation, and concerning the persistence of these responses and their interactions with other ecological stressors.

Progressive behavioural, physiological and transcriptomic shifts over the course of prolonged starvation in ticks

“…Finally, it is worth noting that this study focused on ticks maintained under constant laboratory conditions; however, environmental conditions such as temperature and humidity can dramatically impact energy utilization and starvation survival (Crooks & Randolph, 2006;van Es et al, 1998;Randolph & Storey, 1999;Troughton & Levin, 2007) and conversely, energy reserves can impact survival of environmental stress (Rosendale et al, 2017). For example, it is likely that dehydration and heat stress will increase the breakdown of nutrient reserves and cold periods will delay breakdown (McCue, Terblanche, & Benoit, 2017). The relationship between nutrient reserve and environmental conditions indicate starvation resistance is likely a critical factor for how ticks respond to climate change.…”

Variation in lipid synthesis, but genetic homogeneity, among Leptopilina parasitic wasp populations

“…Storage fat can help overcome harsh environmental conditions, such as times at which food is not available, which is an all‐pervasive challenge for many animals (McCue, Terblanche, & Benoit, 2017). Numerous insects, for example, can survive long periods without food, such as diapause, by accumulating large lipid reserves for use during winter when foraging is impossible (Hahn & Denlinger, 2011).…”

The Costs of Living Together: Immune Responses to the Microbiota and Chronic Gut Inflammation

“…Even single instances of food deprivation can initiate responses that can affect the gastrointestinal tract and the microbiota (132,133). However, there is a distinction between starvation, caused by extrinsic forces, and fasting, initiated by internal stimuli (132). For example, a period of food deprivation during winter is starvation, while hibernation through winter is fasting.…”