Energetics of Insect Diapause

Abstract

Managing metabolic resources is critical for insects during diapause when food sources are limited or unavailable. Insects accumulate reserves prior to diapause, and metabolic depression during diapause promotes reserve conservation. Sufficient reserves must be sequestered to both survive the diapause period and enable postdiapause development that may involve metabolically expensive functions such as metamorphosis or long-distance flight. Nutrient utilization during diapause is a dynamic process, and insects appear capable of sensing their energy reserves and using this information to regulate whether to enter diapause and how long to remain in diapause. Overwintering insects on a tight energy budget are likely to be especially vulnerable to increased temperatures associated with climate change. Molecular mechanisms involved in diapause nutrient regulation remain poorly known, but insulin signaling is likely a major player. We also discuss other possible candidates for diapause-associated nutrient regulation including adipokinetic hormone, neuropeptide F, the cGMP-kinase For, and AMPK.

Population dependent effects of photoperiod on diapause related physiological traits in an invasive beetle (Leptinotarsa decemlineata)

“…Even though metabolic demands are suppressed, basic somatic upkeep and expression of diapause related genes, such as for instance stress tolerance proteins, are required for survival (Grodzicki & Walentynowicz 2011). Therefore insects which diapause as adults typically prepare for overwintering by building large lipid stores in a special organ called the fat body (Hahn & Denlinger 2011). Energy can also be stored in other biochemical forms, for instance as carbohydrates and proteins, but since the energy yield per unit weight in carbohydrates and proteins is much lower than in lipids, lipids are the most common form (Arrese & Soulages 2010).…”

“…If energy stores would be severely depleted after one overwintering season, then a prolonged dormancy of 9 consecutive seasons (without intermittent feeding), should be energetically very challenging (see Hanski 1988). The mechanism by which stored energy is utilized during diapause might therefore be of larger relative importance for overwinter survival (Hahn & Denlinger 2011).…”

“…Beetles might not been exposed to the selection because they are able to shift overwintering burrow depth and location during winter (Milner et al 1992). Thereby beetles can actively choose location of the overwintering hibernaculum in order to avoid stress (Costanzo et al 1998) and potentially also optimize energy expenditure (see Hahn and Denlinger 2011). This plasticity might shield beetles from selection by low winter temperatures for even deeper burrows, or otherwise enhanced cold tolerance.…”

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). Lipids are also a critical component of the egg in oviparous animals (Geister, Lorenz, Hoffmann, & Fischer, 2008; Sloggett & Lorenz, 2008; Sotherland & Rahn, 1987), constituting approximately 30%–40% of total macronutrients in insect eggs (Muller et al., 2017).…”

Side by side? Vascular plant, invertebrate, and microorganism distribution patterns along an alpine to nival elevation gradient

“…Although insects often co-occur with vascular plants in alpine environments, their physiology is differently affected by high-elevation and low-temperature conditions. For instance, the management of metabolic resources of insects through diapause nutrient regulation depends on low-temperature regimes (Hahn and Denlinger 2011). Furthermore, thermoregulation of insects can be facilitated by lower air density at high elevation through a substantial reduction of convective heat loss (Dillon, Frazier, and Dudley 2006).…”