Transcriptomic profiles of consistent risk-taking behaviour across time and contexts in European sea bass

Boldness is known to be a key driver of accessibility to food or reproduction, but also of increased risk including of being predated. Boldness is supposed consistent across time and contexts but studies investigating stability of this trait in variable environments, including in terms of stress load and over long periods of time are scarce. Moreover, underlying molecular components are poorly studied. Here, we report that boldness of 1154 European sea bass, evaluated using group risk-taking tests, is consistent over 7 months and for individuals subjected to multiple environments, including a stressful environment. Differences in risk-taking behaviour were strengthened by differences observed in the responses to a novel environment test; shy individuals displaed higher group dispersion, higher thigmotaxic behaviour and lower activity. Transcriptomic analyses performed on extreme phenotypes revealed that bold individuals display greater expression for genes involved in social and exploration behaviour, and memory in the pituitary, and genes involved in immunity and response to stimulus in the head kidney. This study demonstrates that personality traits come with underpinning molecular signature, especially in organs involved in the endocrine and immune systems. As such, our results may help to depict the state-behaviour feedback, previously proposed as key in shaping personality. Overall design: Risk-taking behavior is assessed in 4 separated tests performed over 7 months in European sea bass. At the end of the experiment, 10 individuals were selected based on their extreme behavioral phenotype (either extremely bold or extremely shy) based on their first 3 tests and euthanized to sample the whole brain, the pituitary and the head kidney. These 30 tissues were snap-frozen until the RNA extraction.