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A still from video provided by researchers that shows glucose-averse German cockroaches avoiding a dab of jelly, which contains glucose, and favoring the peanut butter. (Associated Press)

Evolution Saves Cockroaches From Taking The Bait

May 23, 2013

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Most of us are used to thinking that the evolution of living organisms takes millions of years. But in the case of cockroaches, scientists say the resilient pests have a developed a fast-forward mechanism to save their own exoskeleton.

In a newly published study in the journal Science, a group of researchers conclude that cockroaches have evolved to avoid sweet-tasting poisons by making a subtle change in their body chemistry that makes the bait taste bitter to them.

Cockroaches don't have taste buds, but instead taste hairs. According to The New York Times the researchers:

"... concentrated on those [hairs] around the mouth area and on two types of nerve cells that sense tastes and respond by firing electrical signals to the brain. One responds only to sugars and other sweet substances; the other responds only to bitter substances. Whenever a molecule of something sweet attaches to a sweet detector, it fires electrical impulses and the roach brain senses sweetness, which makes it want to eat whatever it is tasting. Whenever a molecule of something bitter attaches to the bitter detector, that cell fires and the brain senses bitterness, which makes the roach want to avoid that substance.

But somehow the roaches had changed so that the glucose made the bitter detector fire."

How long did it take for cockroaches with a sweet hair to go sour on glucose?

The cockroach glucose aversion "first appeared in the early '90s," Jim Fredericks, chief entomologist at the National Pest Management Association, was quoted by The Times as saying. That's shortly after exterminators started using poison baits instead of spraying as the main method of battling roaches, the newspaper says.

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