Flight capacity drives circadian patterns of metabolic rate and alters resource dynamics

Abstract

Animals must acquire, use, and allocate resources, and this balancing act may be influenced by the circadian clock and life-history strategy. Field (Gryllus) crickets exhibit two distinct life-history strategies during early adulthood-flight-capable females invest in flight muscle at a cost to ovary mass, whereas flight-incapable females instead invest solely into ovaries. In female Gryllus lineaticeps, I investigated the role of life-history strategy in resource (food) acquisition and allocation, and in circadian patterns of energy use. Flight capacity increased the standard metabolic rate (SMR) due to greater late-day SMR and flight-capable crickets exhibited greater circadian rhythmicity in SMR. Flight-capable crickets also ate less food and were less efficient at converting ingested food into body or ovary mass. Thus, investment into flight capacity reduced fecundity and the amount of resources available for allocation to other life-history traits. Given the increasing uncertainty of food availability in many global regions, work in Gryllus may clarify the important roles of food and circadian patterns in life-history evolution in a changing world.

Availability of mates and food influence the plasticity in strategies mediating life‐history tradeoffs in an insect

“…Thus, positive covariation between reproductive and somatic investment can occur when some animals eat more food and allocate heavily toward both reproduction and soma, while those that eat less food allocate little to either trait. Like other animals, Gryllus crickets vary in their feeding patterns (Clark et al 2013, Stahlschmidt 2022, and there was positive covariation between the amount of ovary and somatic tissues gained among our treatment groups. To clarify resource allocation patterns, we accounted for food intake by analyzing tissue conversion efficiencies and incorporating food intake into path analysis.…”

“…We used a 2 × 2 × 2 factorial design to study the independent and interactive effects of environmental treatment (acoustic conditions and food availability) and flight capacity on resource acquisition and allocation. We examined these dynamics during the first six days of adulthood because this period is characterized by intense resource acquisition and allocation in Gryllus crickets -LW females can invest in highly metabolic flight muscle, and SW females can increase ovary mass by 100-fold or more -and it is when the flightreproduction allocation tradeoff peaks (Zera and Larsen 2001, Zera 2005, Stahlschmidt 2022). We also focused on the adult stage because auditory organs of crickets do not develop until their penultimate instar (Kämper 1992).…”

“…LW[h] morph). The physiology and feeding behavior of the LW [h] morph in Gryllus has more similarity to the SW morph relative to the LW[f ] morph (Zera et al 1997, Zera and Larsen 2001, Stahlschmidt 2022, Bonfoey et al 2023. Therefore, the morphs can be categorized into two different life-history strategies during early adulthood -flight-incapable (SW or LW[h]) or flight-capable (LW[f ]) -that are mediated by a genetic polymorphism and an environmental polyphenism (Zera 2005).…”

“…(2) Increased food availability will favor reproduction over soma given 1) the energetic costs of reproductive investment in Gryllus (females can increase ovary mass by 100fold or more in the first week of adulthood: Zera and Larsen 2001, Zera 2005, Stahlschmidt 2022) and 2) the potential drawback of food ingestion on flight capacity in insects (i.e. increased abdominal mass requires greater thrust during flight and may compress tracheal volume: Srygley and Kingsolver 2000, Berwaerts et al 2002, Srygley 2018, Urca et al 2021.…”

Hot and scared: how do heatwaves and predation risk impact resource acquisition and allocation?

“…We used a 2 × 2 factorial design to study the independent and interactive effects of environmental treatment (predation risk and temperature) on resource acquisition and allocation. We examined these dynamics during the first 6 days of adulthood because this period is characterized by intense resource acquisition and allocation in Gryllus crickets-SW (short-winged) females can increase ovary mass by 100-fold or more [30,31]. Gryllus adults typically live only 2 weeks or less in the field [32], meaning our 6 days study period spanned approximately half of the crickets' natural lifespan.…”