International - Locust swarms 'high' on serotonin

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Locust swarms 'high' on serotonin

It is one of nature's most radical transformations - the moment a crowd of harmless desert locusts begins to swarm into a devastating plague.

Now scientists from the UK and Australia say they have discovered the trigger - the brain chemical serotonin.

The molecule is best known in humans as a target of anti-depressant drugs.

The discovery could lead to new control strategies for the pests, which plague 20% of the world's land, they write in Science journal.


"To find that serotonin is what causes a normally shy, antisocial insect to gang up in huge groups is amazing" -Dr Swidbert Ott, Cambridge University

Desert locusts are known to swarm by the billions, inflicting severe hardship on farmers in parts of Africa, China and other areas.

But the insects actually spend much of their life in a harmless, "solitary" phase.

Passive aggressive

When food runs short, they slowly become clustered together and enter their "gregarious" phase, culminating in an aggressive swarm.
Locusts swarm in gregarious phase
Swarms can devastate crops and cause serious economic hardship

Prior to swarming, the locusts undergo a series of dramatic physical changes - their body colour darkens and their muscles grow stronger.

To find out the chemical signal that triggers this metamorphosis, scientists from Oxford University, Cambridge University and Sydney University began monitoring locusts in the laboratory.

They triggered the gregarious behaviour by tickling the beasts' hind legs, to simulate the jostling they experience in a crowd.

They found that locusts behaving the most gregariously (in swarm-mode) had approximately three times more serotonin in their systems than their calm, solitary comrades.

"The question of how locusts transform their behaviour in this way has puzzled scientists for almost 90 years," said co-author Dr Michael Anstey, from Oxford University.

"We knew the [physical] stimuli that cause locusts' amazing Jekyll and Hyde-style transformation.

Source: http://news.bbc.co.uk/1/hi/sci/tech/7858996.stm VIDEO AVAILABLE AT SOURCE

# BBC News
# January 29, 2009

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Highly interesting stuff