Department of Physics, Chemistry and Biology (IFM)

Consistent behaviour was observed for  boldness, activity and exploration. These are behaviours used to describe variation in personality before. Personality was not observed for aggressiveness and sociability. Both of these are traits related to interactions with conspecifics and, it is possible, that these behaviours were affected by dietary stress more than others. Differences in repeatability are commonly observed across studies, adding to discussion of what explains variation in personality.

Only aggression was affected with restricted diet fish showing less of it.  In previous studies, infected hosts showed change to different traits – boldness, activity and social behaviour. It is possible, that the treatment used in present study imposed only mild dietary stress and, with no infected individuals to enhance effects of restricted feeding, was insufficient to generate stronger behavioural effects. However, higher mortality observed in restricted feeding group implies that dietary restrictions were sufficient to have an impact.

Elevated levels of serotonin are associated with reduced aggression in previous studies. Higher turnover rates in females and lighter fish imply that dieatary restriction causes more stress in these 2 groups.

Reduced diet fish showed higher expression levels for dopamine transporter DAT and dopamine receptor drd2b. It is possible that DAT plays a similar role in stickleback physiology, thus upregulated DAT expression could be linked to difference in stickleback aggression between two dietary treatments. Upregulated expression of drd2b gene has been observed in bolder zebrafish and drd2 genes have been associated with behavioural changes in boldness and aggression in number of model animals. Again, the upregulated drd2b gene expression could thus be associated with increase in aggressive behaviour.

Changes resulting from dietary stress differ from previously observed variation associated with parasitic infections, thus dietary stress alone cannot explain the observed differences in infected organism and other modifying factors, such as infection, should be considered.