Octopamine Signaling Mediates Thermal Stress Adaptation in Drosophila melanogaster

ABSTRACT Thermal fluctuations strongly influence ectotherm physiology. Although octopamine (OA) is a key regulator of insect stress physiology, including thermal stress, the receptor‐specific mechanisms by which individual octopamine receptors coordinate thermal tolerance, survival, and life‐history traits remain poorly understood. Here, we examined OA titres and thermal responses in Drosophila melanogaster repeatedly exposed to heat (35°C) or cold (15°C) stress and assessed four OA receptor‐deficient flies (Octβ1R, Octβ2R, Octβ3R, OctαR). OA concentrations increased by 46% under heat stress and decreased by 39% under cold exposure compared with 25°C controls, confirming temperature‐dependent modulation. Survival analyses revealed strong receptor specificity: Octβ3R and Octβ2R‐deficient flies exhibited markedly reduced longevity at 35°C (median survival 12 and 21 days, respectively, vs. 29 days in controls). A significant reduction in fecundity of the Octβ2R ‐ deficient flies was observed at 35°C compared to all groups. The OctαR‐deficient flies showed increased egg production, but reduced offspring emergence. Thermal stress also induced receptor‐dependent changes in development time and sex ratio. These findings demonstrate that individual octopamine receptors differentially regulate thermal stress tolerance and thermally induced life‐history trade‐offs, identifying OA receptor‐mediated signaling as a key physiological pathway shaping insect responses to temperature variation.