Later developmental stages of Drosophila melanogaster acclimate and function better in response to thermal stress than early developmental stages.

Animal development is a complex process that requires successful completion of multiple steps at different developmental stages to produce adult organs and systems. Environmental stress experienced during crucial developmental stages could therefore disrupt the proper functioning and survival of individuals as adults long after the stressor has passed. Early embryonic stages, in particular, may be particularly susceptible to long-lasting effects because cellular mechanisms of stress resistance are relatively underdeveloped. Drosophila melanogaster acts as a model species, developing important structures like wings and heat resistance systems over time after embryogenesis. In this study, I tested the impact of when thermal stress is applied to pre-adult flies and what impact that had on performance and phenotypic traits as adults. This was accomplished by placing flies in incubators with abnormal temperatures during later developmental stages, including 24 hours post laying, and testing whether later developmental stages acclimated better to thermal stress than early developmental stages. When eggs were laid, they were reared at 25°C for 1 or 24 hours before being transferred to incubators that applied thermal stress that mimicked natural hyperthermia and hypothermia experienced in nature. Moderate thermal stress applied to eggs one hour after laying caused many phenotypic consequences in adulthood. Flies with this treatment experienced a high proportion of deformed wings and many of the pupae failed to eclose into adults. It is expected that thermal stress applied during early embryonic stages disrupts the proper growth and functioning of flies and results in lasting phenotypic consequences. 24-hour flies were found to have a greater proportion of properly developed wings, eclosed from pupae into adults at a higher proportion, and displayed superior upper and lower thermal limits than 1-hour flies. Later developmental stages acclimated better to moderate thermal stress and incurred fewer lasting phenotypic consequences as a result of that thermal stress compared to early developmental stages. By understanding how various developmental stages resisted the deleterious effects of thermal stress, we learned more about when crucial stages in development occur and when D. melanogaster’s ability to resist the effects of thermal stress becomes effective. Due to temperature being an integral factor of D. melanogaster development, female flies should select locations for laying their eggs in nature that are around 25°C, whether that means seeking out shade in hotter climates or seeking out areas constantly exposed to the sun in colder climates