Within many animal species, individuals exhibit different personalities. For example, some individuals are consistently more bold than others.
"But in biology we still do not fully understand what lies behind the fact that people or animals exhibit different personalities. In humans, people with different levels of signal substances in the brain, such as serotonin or dopamine, tend to behave differently. But we do not know if variations in these signal substances can explain differences in personality in other species, and if the signal substances cause the observed differences, or whether both the differences in behavior and levels of signal substances depend on another underlying factor, says Robin Abbey-Lee, postdoctoral at the Department of Physics, Chemistry and Biology, IFM, one of the researchers who led the study.
Gave crickets medicine to humans
The researchers therefore wanted to actively change the levels of the serotonin and dopamine signaling agents to investigate this, and used crickets for the study. They did it by giving crickets drugs that affect the serotonin and dopamine systems, and used to treat people in depression or Parkinson's disease. Because the serotonin and dopamine systems of different animals are similar to each other, researchers expected the drugs to also affect crickets.
"In this study, we wanted to gain an important knowledge gap by experimentally changing the levels of these signal substances and see if it could result in a behavioral change in cysts," says Hanne Løvlie, Assistant Professor at IFM, who has studied the study.
Then measured the cricket's behaviors
The researchers measured three different behaviors in the cysts.
"We measured how active crickets were in a familiar environment. It corresponds to how much a person moves around in his own home. We also investigated the exploratory behavior of the cricket in a new environment, similar to how a person can behave in a visit to a new city. Finally, we studied how the crickets behaved in a combat situation to measure the aggressiveness of individuals, says Robin Abbey-Lee.
The researchers found that changing serotonin levels made the crickets less active and less aggressive. Changed dopamine levels, on the other hand, were not associated with behavioral changes in the cysts.
"This indicates that serotonin has a clearer underlying role in these behaviors," says Hanne Løvlie.
The findings increase our understanding of why animals have personality. They also raise the issue of how drugs that leak into nature via our wastewater affect wildlife.
"Experimental manipulation of monoamines levels alters personality in crickets", Abbey-Lee RN, Uhrig EJ, Garnham L, Lundgren K, Child S, LøvlieH, (2018), Scientific Reports, published online November 1, 2018