Insect Behavior and Physiological Adaptation Mechanisms Under Starvation Stress

Abstract

Intermittent food shortages are commonly encountered in the wild. During winter or starvation stress, mammals often choose to hibernate while insects—in the form of eggs, mature larvae, pupae, or adults opt to enter diapause. In response to food shortages, insects may try to find sufficient food to maintain normal growth and metabolism through distribution of populations or even migration. In the face of hunger or starvation, insect responses can include changes in behavior and/or maintenance of a low metabolic rate through physiological adaptations or regulation. For instance, in order to maintain homeostasis of the blood sugar, trehalose under starvation stress, other sugars can be transformed to sustain basic energy metabolism. Furthermore, as the severity of starvation increases, lipids (especially triglycerides) are broken down to improve hunger resistance. Starvation stress simultaneously initiates a series of neural signals and hormone regulation processes in insects. These processes involve neurons or neuropeptides, immunity-related genes, levels of autophagy, heat shock proteins and juvenile hormone levels which maintain lower levels of physiological metabolic activity. This work focuses on hunger stress in insects and reviews its effects on behavior, energy reserve utilization, and physiological regulation. In summary, we highlight the diversity in adaptive strategies of insects to hunger stress and provides potential ideas to improve hunger resistance and cold storage development of natural enemy insects. This gist of literature on insects also broadens our understanding of the factors that dictate phenotypic plasticity in adjusting development and life histories around nutritionally optimal environmental conditions.

The distinct phenotypic signatures of dispersal and stress in an arthropod model: from physiology to life history

“…Sample sizes, from left to right: (A) 40, 40, 40, 40 independent mites, (B) 31, 29, 7, 7 independent mites. despite amino acids also being a potential source of energy under stressful contexts (Zhang et al, 2019), several organic acids being involved in the energetic metabolism (lactic and citric acid cycles), and accumulation of compatible solutes, in the form of polyols, being documented in response to several stressful contexts, including food stress (such as substrate enriched in urea owing to high population densities; Henry et al, 2018). Nonetheless, our results are in line with those of previous studies.…”

“…This is a physiological signature of a starved state, characterized by individuals relying on, and depleting, their body reserves, including carbohydrates (e.g. Dus et al, 2011;Shi et al, 2017;Zhang et al, 2019). Surprisingly, there were no other metabolic differences between tomato-and bean-exposed mites, Fig.…”

“…Starvation, i.e. the most severe form of food stress, affects the activity of several metabolic pathways, resulting in reductions of the quantities of essential amino acids as well as the use of energetic stores (Maity et al, 2012;Zhang et al, 2019). Tolerance to more limited food stress, e.g.…”

Regulation of Carbohydrate Metabolism by Trehalose-6-Phosphate Synthase 3 in the Brown Planthopper, Nilaparvata lugens

“…The highest level of TPS expression at one age of larval stage was found in A. mellifera and Bactrocera minax (Xiong et al, 2016;Łopieńska-Biernat et al, 2018). Differently, the highest expression was found in the adult stage of M. domestica (Zhang D. W. et al, 2019) and in the early pupa of H. vitessoides (Chen et al, 2020). In addition, the glucose content was low in the 4th instar, rich in the early 5th instar, and remained stable and abundant in the adult population.…”

Nutritional availability and larval density dependence in Aedes aegypti

“…Second, stressed conditions early in the larval lifespan may encourage adaptive responses that promote development. In some insect species, hunger stress has been observed to induce physiological countermeasures that improve the insect's ability to endure nutritional shortages (Zhang et al, 2019). In honeybees (Apis mellifera), for example, periods of starvation resulted in physiological changes such as improved glycogen storage among others, which facilitated survival in nutrient-poor environments (Wang et al, 2016).…”