During this fellowship, I conducted experimental work using Japanese quail, from eggs to adult birds. I optimized incubation conditions of eggs to be able to accelerate, decelerate or alter the stability of embryo development using variations in incubation temperature. I also used eggs coming from selection lines that have been selected for a low or a high maternal investment as measured by egg size, to test the importance of pre-natal resource availability.
I collected data on embryo development such as organ size and heart rate, and biological samples (blood, brain and heart) from a subsample of embryos. I found that developmental conditions have a profound impact on heart morphology and function, especially with slow development being associated with a slow heart rate and an increased heart size. I conducted biochemical and molecular analysis to measure markers related to the ageing process. Analysis of results is still ongoing, but it seems that telomere length is unaffected by developmental rate or stability, but is reduced in embryos having low resource availability during development (i.e. from small eggs). Developmental conditions also had an impact on mitochondrial function (the powerhouse of eukaryotic cells), since unstable developmental conditions were associated with more active mitochondria in the brain, and low resource availability was associated with impaired mitochondrial function in both the heart and the brain. Finally, unstable development was also associated with a rise in plasma stress hormones in embryos, suggesting a role of developmental stability in programming stress physiology prenatally.
I also collected data on birds postnatally, from hatching to adulthood, about their morphology, reproduction, behaviour and physiology. Overall, incubation temperature did not alter growth rate and adult morphology, but I found marked differences in behaviour and physiology. First, chicks developing under unstable conditions were less stressed and more explorative. Second, developmental conditions had no significant impact on reproductive traits measured as testis size for males and cumulative egg production (size and number) for females. Finally, developmental conditions had a clear-cut effect on telomere dynamics with age, with birds having shorter telomeres when developing fast, under less stable conditions or with less resource available. Therefore, poor conditions experienced during embryo development appear as a major determinant of telomere length, which could mediate the known long-term impact of poor early-life conditions on subsequent health.
The results of this project have been presented at several national and international conferences, including two symposia on the diversity of telomere dynamics organized in Edinburgh in 2016 and 2017, which were ideal opportunities to present my research to a broad range of scientists (from ecologists to epidemiologists) interested in telomeres and ageing. In addition, I finished this fellowship by presenting my research at the Society for Integrative and Comparative Biology Annual Meeting in San Francisco in January 2018, which enabled me to reach a broad audience across North America, and opened new perspectives for transatlantic collaborations.
