The brain chemical serotonin triggers one of nature’s most astounding transformations, which happens when solitary placid desert locusts converge into terrifying plant-devouring swarms, scientists have found.
When driven by fluctuating environmental cycles and the compulsion to eat, locusts alter not only their behavior, but their size, strength and color as well. In fact, the change in appearance is so dramatic that until the 1920s scientists thought the two phases of locust existence were actually two separate species.
Researchers led by Michael Anstey of Oxford University in the UK studied changes in locust behavior
and tested them with a variety of chemicals. They found that when the insects were swarming, they had three times more serotonin
in their systems than when they were living alone.
"Up until now, whilst we knew the stimuli that cause locusts' amazing 'Jekyll and Hyde'-style transformation, nobody had been able to identify the changes in the nervous system that turn antisocial locusts into monstrous swarms,”Dr. Anstey explained
in an academic press release. "The question of how locusts transform their behavior in this way has puzzled scientists for almost 90 years, now we finally have the evidence to provide an answer.” The researchers found that drugs that block serotonin made locusts shy
, even when other factors suggested they congregate, and drugs that boost serotonin made solitary locusts suddenly gregarious. Serotonin, which carries nerve signals in nearly all animals, plays a role in human moods, emotions and desires.
Dr. Anstey, and colleaguesStephen M. Rogers
, of Oxford and Cambridge Universities, Swidbert R. Ott, and Malcolm Burrows
, of Cambridge and Stephen J. Simpson of the University of Sydney in Australia, reported their findings in a paper published in the January 30 issue of Science magazine.
Dr. Rogers says locusts are finely tuned to adjust
to their dry but changeable desert environment. In dry periods, they are fairly antisocial, existing as harmless green grasshoppers. After the occasional rainstorm, locusts gather to follow the newly increased vegetation, heading out from the driest regions into more fertile adjacent lands. As they see, smell or touch other locusts, their behavior and appearance transforms in a matter of hours. Their darker color scares predators, and their stronger muscles and bigger wings let them make long migratory trips, flying 60 miles in five to eight hours.
It’s one of nature’s cruelest tricks, says Dr. Rogers: Farmers rejoice with rain and then see their crops are devoured. Locust swarms affect 20 percent of the earth’s land mass and have occurred periodically in Africa, Asia, Australia and the western US. The Old Testament, describing the Eighth Plague of Egypt, says locusts shall cover the face of the earth, fill every house and eat everything that grows. The prophet Joel also warned of locusts coming in deadly clouds. The researchers suggest in their Science article that the discovery could lead to new pest control strategies.
Darwin’s 200th Birthday and the 150th anniversary of The Origin of the Species: The New York Times carried several articles commemorating Charles Darwin, including Olivia Judson’s thoughtful piece, The Origin of Darwin