How do animals cope with stress in different environments? (Ref 4595)

Project Background

We know that all organisms have a stress response system to cope with environmental challenges, yet its precise form varies hugely within and between individuals. At its heart, a stress response system should be able to throw everything at responding to a stressor (fighting, fleeing), but at the same time it should minimise disruption to the animal's other physiological systems. Recently, we have identified that stressor predictability is likely to be a major driver of variation in stress responses. This project further examine this hypothesis. You will be trained in computer programming and modelling techniques (such as control theory) to predict what key features and limitations of stress response systems evolve across different environments. We then put these models on stressor predictability to the test by using lab experiments and field work in the Mediterranean field cricket Gryllus bimaculatus.

Project Aims and Methods

Below we suggest three potential components of this PhD project to study the evolution of stress responses in animals. Of course, we encourage you to think about different components that are closer to your interests, as we believe that PhD students should lead the design of their projects.

1. Evolutionary models of stress response systems In this part of the project you will receive training in mathematical modelling in biology, where you will learn how to use control theory to develop an evolutionary model of a stress response. You can then use these skills to analyze what features characterize stress response systems that experience fluctuations in stressor occurrence. These models then allow one to predict how key features of stress response systems (e.g., robustness, damage accumulation) vary with different environments. Moreover, they also can inform us how changes in condition (e.g., medical interventions, chronic stress) affect the stress response.

2. Experimentally measure how stressor predictability affects the stress response Crickets are a great model organism to the study of stress responses as the underlying stress response pathways are starting to be discovered and its genome has recently been sequenced. We will expose crickets to signals that indicate predation (e.g., scent of predators like the common toad). Stress responses are measured through hormones such as octopamine, which is a key component of the insect stress hormone pathway. Existing models made by us show that predictable vs random occurrences of stressors should affect the magnitude of the stress response. In this part of the project we aim to test this prediction by comparing different treatment groups that vary in the predictability of stressor occurrence vs absence during development.

3. Field work on naturally occurring stressors in cricket populations in Portugal We aim to compare stress responses in field populations of Gryllus bimaculatus across Portugal, which differ in composition and density of predators. Moreover, we can also experimentally manipulate stressor occurrence by using protective cages that keep out key predators such as snakes, toads and mice.