Defence on demand

Anti-predator traits in prey organisms are widespread and diverse, including e.g. behavioural, chemical and morphological adaptations. Extensive research during recent years have shown that many prey are able to fine tune the expression of the adaptive defences to the current risk of predation, i.e. they have inducible defences. However, at this point very few studies have addressed the proximate mechanisms underlying this phenotypic plasticity, and this is a critical gap if we want to advance our understanding of the evolution and constraints of phenotypically plastic defence traits.

The main goal with my PhD project is hence to get a more mechanistic understanding of how inducible defences operate among vertebrate prey species. In this research we are using the crucian carp, Carassius carassius, as a model organism. This fish provided the first example of an inducible morphological defence in a vertebrate and now I will investigate the physiological mechanism behind the increase in body depth (see figure below) in crucian carp when exposed to chemical cues from fish predators.

I will start with a study of the interaction between a neuroendocrine stress axis and the expression of defence traits. Here, cortisol is a key hormone that underlies the “fight and flight-mode” in stressed individuals. As a first step, I will test this hypothesis by experimentally manipulate cortisol levels and see how that influence the expression of multiple defence traits in the crucian carp.