Metabolic depression drives discontinuous gas exchange in diapause pupae of Sericinus montelus (Lepidoptera: Papilionidae): a seasonal adaptation strategy.

Adaptive shifts in respiratory patterns during insect diapause represent a key strategy for coping with seasonal adversity, yet the underlying regulatory mechanisms remain poorly understood. Using the swallowtail butterfly Sericinus montelus Gray as a model, this study investigated the regulatory roles of diapause and temperature on respiratory patterns by comparing gas exchange patterns and metabolic characteristics of pupae under different photoperiods and temperature conditions. The results demonstrated that the metabolic rate of diapause-destined pupae was significantly lower than that of non-diapause pupae, and they stably maintained a discontinuous gas exchange (DGE) pattern. In contrast, all non-diapause individuals exhibited continuous gas exchange. Temperature influenced the respiratory pattern by modulating the metabolic rate: diapause-destined pupae maintained DGE across the entire temperature range tested, while non-diapause pupae displayed DGE at lower temperatures but switched to continuous gas exchange at higher temperatures, suggesting the existence of a metabolic rate threshold triggering the transition. Furthermore, DGE cycle parameters were regulated by both temperature and diapause duration: low temperature and diapause progression significantly extended the interburst period and the total DGE cycle duration, while the volume of CO2 released per burst remained stable, which is consistent with the hygric hypothesis for DGE. This study identifies photoperiod-induced metabolic depression as the core driver of the DGE pattern in diapausing S. montelus pupae, with temperature fine-tuning the cycle parameters via its effect on metabolic rate. Together, these mechanisms optimize energy conservation and potentially reduce water loss, highlighting a key physiological adaptation that may vary across insect taxa.