A new study has shown that crayfish, those "delicious" beings some people choose to eat, actually feel stress and respond the same as humans when given a drug used to treat anxiety. The results of this very interesting study are reported in the prestigious journal, Science, in an essay titled "Anxiety-like behavior in crayfish is controlled by serotonin." (However, it is only available to subscribers.)
The research team lead by Pascal Fossat in the Department of Life Science and Health, Université de Bordeaux (France), concluded that this research "may alter our conceptions of the emotional status of invertebrates." When Professor Fossat and his colleagues mildly shocked crayfish, they placed them in an aquarium maze containing pathways that were well lit and dark. The shocked and stressed crayfish strongly preferred the dark paths and rarely entered the lighted ones, whereas the non-stressed crayfish also preferred the dark pathways but also entered the lighted ones.
What is incredibly interesting is that light avoidance by the stressed crayfish is associated with heightened levels of the brain neurotransmitter serotonin that also is associated with human moods. In addition, injecting crayfish with serotonin made them anxious and treating them with the drug chlordiazepoxide that's used to treat anxiety in humans reduced the anxiety in the stressed individuals. They then entered lighted pathways.