Einstein Science Reporting for Kids
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21-Apr-2005

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Taste test for ants




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Scientists put a bunch of ants through a taste test.

No. The scientists didn't taste the ants. The ants did the tasting. The ants wandered around an "ant cafeteria" where they could eat any of the natural or artificial sweet foods they wanted.

The scientists recorded which ants liked which foods. Using these taste test results, the scientists set up more experiments.

The results of this next round of experiments helps explain why some plants and ants appear so devoted to one another. 2005 issue of the journal Science. In particular, the new research looks at the relationship between the ants that protect certain plants from other insects, plants and diseases. In return for their work, the ants get a place to live as well as nectar to eat.

The scientists have discovered that some plants make sweet nectar that only tastes good to the "security guard" or helper ants.

Freeloading ants looking for a free meal do not like the sweet nectar produced by these plants, so they ignore the free food.

In fact, freeloading ants don't just dislike the free food. They can't break down the sweet nectar and use it for food. Only the ants that have developed a special "I help you, you help me" relationship with the plants can digest this nectar.

To get an idea how this situation developed in nature, imagine the following situation:

You are a professional gardener with a serious green thumb. The manager of a famous garden has hired you to manage the garden which attracts visitors from all over the world. In return for your service, you will receive a place to live and wonderful meals.

You work hard. The plants, trees and bushes are lush, healthy and beautiful. The garden has a chef who leaves your lunch and dinner on a garden patio each day for you and your staff. You like to eat while enjoying the fresh air and scenery.

Over time, you notice that garden visitors start coming over and eating some of your food before you get there. You're upset because they are eating YOUR food. If this keeps up, you might want to find a different job. The other devoted gardeners are upset too.

The owners of the garden are also unhappy because they do not want to lose such a wonderful group of gardeners. Also, the garden chef is spending money, effort and time to make you this nice food in return for your work. She doesn't want the visitors stealing your food.

What should the gardener and garden owners do?

There are lots of ways the people at the garden could solve this problem. For example, a small sign on the table that says, "Do Not Eat. Staff Only" might do the trick. Or the gardeners could eat inside.

Ants and plants can't rely on signs made of words and they can't go into a "cafeteria" inside the plant. They need other strategies.

Martin Heil and Wilhelm Boland from the Max-Planck-Institute for Chemical Ecology in Essen, Germany have discovered one strategy.

These scientists say the plant actually makes food that only the helper ants can eat. And the digestive system of the helper ants developed so that it can only eat this special kind of food, and not the more common type of food.

There is one more twist to this story. The plants produce "regular" nectar that would be tasty to all ants. But once the nectar is outside the plant, a chemical reaction takes place that makes the nectar only edible to the security guard ants.

Just as it's hard to imagine ants posting signs made of words, it's hard to imagine a chef making food that then suddenly goes through a chemical reaction that makes the food only edible to the gardeners. And it's even stranger to think that the garden staff would not be able to eat "regular food," just as the helper ants cannot eat the "regular" nectar that most ants enjoy.

But then again, it's hard to imagine having six legs like an ant, or using the sun's rays to make my own food, like a plant.

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A scientific paper describing these results appears in the 22 April,