Regulation of Metabolic Rate during Preceding Arousal Periods May Play a Part in the Variation, in Length, of Metabolic Depressions During Insect Dormancy

Metabolic regulation presents itself as a target across the biological and biomedical fields of research. Understanding the control mechanisms that underlie metabolic efficiency and adaptation promises a great many things - from novel drug targets to forecasting the effects of our changing climates on our fauna and flora. During diapause (developmental hibernation), Sarcophaga crassipalpis (Macquart's flesh fly) showcases a profound route of metabolic regulation. Flesh fly pupae undergo metabolic cycles of varying lengths, maintaining long and inconsistent periods (4-10 days) of metabolic suppression interspersed with short and consistent (24-36 hours) periods of metabolic arousal. The significance of the differing cycle lengths, which stem from variation in depression periods, remains underexplored. However, previous research has shown that these cycles and transitions between periods are regulated by reactive oxygen species (ROS) signaling, with high levels of ROS triggering a transition from arousal to depression and vice versa. Given that ROS is primarily produced during arousal - when aerobic metabolism resumes - we hypothesize that the arousal period, via the magnitude of oxygen metabolism, regulates the length of the subsequent depression period and thereby sets the temporal structure of diapause. To investigate this, we measure whole-organism oxygen consumption (VO₂) as well as CO2 production in pupae over extended time courses using a custom-built stop-flow respirometry system. By quantifying the relationship between VO₂ during arousal periods and the duration of following depression bouts; as well as between post-arousal ROS and duration of following depression, we aim to determine whether the arousal state encodes a "metabolic signature" that temporally structures diapause. This work provides a window into natural models of metabolic suppression and oxidative regulation - mechanisms that may inform biomedical strategies and deepen our understanding of metabolic plasticity and regulation strategies.