April 16, 2014, BY Matt Hughes

This laser confocal image of a fruit fly head provided by Chris Dunne ’15 highlights the fly's mushroom bodies, the l-shaped structures near the top of its head.
This laser confocal image of a fruit fly head provided by Chris Dunne ’15 highlights the fly's mushroom bodies, the l-shaped structures near the top of its head.

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The next time you swat a fruit fly away from the bananas on your counter, think about this: You can cover the fruit, hide it away in a cabinet or the fridge, but the next generation of flies might come back smarter than before.

This insight comes thanks to the work of Professor Elizabeth Marin, biology, who has found compelling evidence that depriving Drosophila melanogaster, the common fruit fly, of nutrition during development increases growth in brain structures that help the fly learn and remember food sources.

Marin is an expert in fruit flies, especially their neurologic development. If that sounds pedestrian, consider this: Scientists have been studying Drosophila for more than 100 years, and know more about these common pests than they do about almost any other animal. One reason for their intense interest in Drosophila is that the flies share some genetic commonalities with humans, and their short lifespans, low cost and copious broods make them attractive for genetic research.

"Lots of genes involved with cancer were discovered in Drosophila originally," Marin said. "Lots of developmental patterning genes that we know are common to all animals were discovered in Drosophila."

For a paper published in Current Biology, Marin worked with nine scientists from around the U.S. to tell a fascinating story about the development of mushroom bodies, the fruit fly's learning and memory brain structure — comparable to the hippocampus in humans. The paper represents multiple experiments and five to six years of research, Marin said.

In one experiment, scientists placed Drosophila larvae in sugar water, providing them enough energy to stay alive but depriving them of the fats and proteins they need to develop. The flies entered a static state, surviving but not growing — except for their mushroom bodies. The mushroom body stem cells continued to divide, potentially producing a smarter fly.

"They were essentially cannibalizing themselves in order to keep growing their brains, even though they were being starved," Marin said.

The researchers also examined a separate brain structure related to scent processing, which is actually connected to the mushroom body, and found its development was not impacted by nutrition. For that reason, Marin and her collaborators hypothesize the link between mushroom body growth and nutrition may have an evolutionary purpose.

"If they're in a situation where they don't have a lot of nutrition and they're competing for resources, then they're growing up in a world that forces them to be smarter in order to locate food and find it again," she explained. "So they make bigger mushroom bodies while they're developing, and then if they make it to adulthood, they'll be smarter, and they'll be able to find and remember food sources for the next generation, so that they can find them and lay their eggs on them."

In other words, the harder you try to hide your food from Drosophila, the smarter the next week's generation of little buggers might get. Food for thought for scientists and fruit lovers alike.