Climate Change Solutions: Developmental Programming of Fish Thermal Tolerance Limits

Climate change poses a significant threat to global biodiversity. Conservation strategies are critically dependent on a thorough understanding of the effects of fluctuating environments on animal morphology, physiology and behaviour. While environmental stress can affect animals across their life course, organisms are particularly vulnerable during embryonic development. Importantly, fluctuations in the embryonic environment can trigger epigenetic modifications of gene expression which can alter the developmental trajectory of animals. This phenomenon, known as developmental programming, can lead to permanent changes in organismal structure, function and behaviour which can influence life-time fitness1. Given the implications of developmental programming, it has become crucial to understand the effects of climate change on animal developmental plasticity.

Despite the fact our planet is warming, we know very little about the mechanisms underlying thermal plasticity during development and how they may influence an organism’s life-time fitness. Fish are particularly vulnerable to global warming and developmental programming because they are ectothermic vertebrates that can’t control their body temperature. Developmental temperature is well-known to affect multiple life history traits in fish, including sex determination, body shape and swimming performance. Interestingly, new research suggests early exposure to warm temperatures during development may influence thermal acclimation capacities in adulthood2,3. Therefore, thermal programming may represent a promising tool to help fish cope with higher temperatures in future climate-change scenarios.

While the implications of thermal programming of thermal tolerance are far-reaching, the mechanisms underlying this phenomenon are very poorly understood. Recent work suggests aspects of cardiac structure and function are programmed by temperature in fish4, which suggests the intrinsic properties of the heart have changed. Given that maintained cardiac function is central to surviving warm temperatures, we propose that thermal programming of acclimation capacities in fish occurs via epigenetic modification of cardiac excitation-contraction coupling pathways which increase the thermal tolerance limits of the heart. Therefore, this project will use epifluorescent microscopy, electrophysiology and whole-animal in vivo respirometry to assess the long-term impact of developmental temperature on cardiac function and thermal tolerance limits. Furthermore, transcriptomics and epigenetic analysis (methylation patterns) will be used to identify molecular mechanisms that confer thermal tolerance.

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