When attracted to the smell of popcorn with butter, foodless nematodes are more likely to cross the toxic copper barrier to reach the smell of snacks than their well-fed counterparts.


May 5, 2022

Nematodes are willing to take risks to follow the smell of snacks


Hungry worms are more likely than saturated worms to cross the toxic copper barrier to reach the aroma of food.

Although there is much anecdotal evidence that hunger can cause animals to act impulsively, less is known about how hunger is signaled in the brain and how this signal shapes choices.

To better understand how hunger changes behavior, Srikant Chalasani at the Salk Institute in California, and his team turned to transparent roundworms called nematodes. They aimed to answer three key questions: how does hunger affect what happens in the worm’s body, how is this change transmitted to the brain, and how does this ultimately shape choice?

The researchers placed about 60 nematodes (Caenorhabditis elegans) on the one hand a barrier of honey, which is toxic to them, and on the other hand there is the smell of popcorn with butter. Half of the worms had not eaten for 3 hours, while the others had eaten a recent meal.

Chalasani and his colleagues found that about 80% of hungry worms pass through repellent honey to reach food, compared to about 20% of their well-fed counterparts. When hungry worms were fed, they returned to the less risky behavior of saturated worms.

“If [the worm] If there is a lack of food, he thinks, “I’m going to take that risk because I’m getting hungrier and hungrier, so I have to work hard to cross that barrier,” Chalasani said.

After demonstrating that starving worms take bold action to get to the smell of food, Chalasani wanted to know what mechanism triggers the hunger signal to the brain.

Genetic and imaging analysis points to certain proteins in the intestinal cells of worms that can tell the brain that the intestines need food. Researchers have also identified a receptor in the brain that they suspect captures the signal.

“Then the gut tells the brain and the brain changes behavior,” Chalasani said. “It was a little surprising. We did not expect the worm to have this level of sophistication.

The work may help explain why some people behave irrationally when they miss a meal, as the basic biological patterns in nematodes are often translated into humans. But Chalasani notes that being “hungry” does not justify bad behavior. “I may be hungry and still not show it because [unlike a worm] my brain has the sophistication to suppress some of those feelings. “

Reference in the magazine: PLOS Genetics, DOI: 10.1371 / journal.pgen.1010178

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