A chemical that affects people's moods also can transform easygoing desert locusts into terrifying swarms that ravage the countryside, scientists report.
“Here we have a solitary and lonely creature, the desert locust. But just give them a little serotonin, and they go and join a gang,” observed Malcolm Burrows of the University of Cambridge in England.
The brain chemical serotonin has been linked to mood in people. It plays a role in sexual desire, appetite, sleep, memory and learning, too.
Under certain conditions, locusts triple the amount of serotonin in their systems, changing the insects from loners to pack animals, Burrows and his co-authors report in Friday's edition of the journal Science.
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These packs can be devastating. Last year a swarm nearly four miles long plagued Australia. They occur in Africa and Asia and the Western U.S.
“Serotonin profoundly influences how we humans behave and interact, said co-author Swidbert Ott of Cambridge, “so to find that the same chemical in the brain is what causes a normally shy anti-social insect to gang up in huge groups is amazing.”
The scientists took some solitary locusts and injected serotonin into them. Sure enough they changed in appearance and flocked together.
The Dr. Jekyll to Mr. Hyde transformation took only a few hours.
It turns out that locusts produce more serotonin when circumstances force them together and they are stimulated by the sight, smell and touch of many other locusts.
Once researchers determined that serotonin causes the change, they gave locusts drugs that blocked serotonin and then exposed them to situations that normally cause swarming. But the change didn't occur.