Dartmouth Researchers Discover That Fruit Fly Species Use Social Learning to Protect Offspring

Drosophila melanogaster (Photo: Shutterstock)

Fruit flies (Drosophila melanogaster) have a number of attributes that have made them one of the most extensively studied and well understood of all model organisms used in biomedical research. These include sharing many of the genes that cause diseases in humans, having a relatively small genome (fully sequenced in 2000), a short life cycle, and a large number of offspring.

Still, as findings from a Dartmouth study published last week in the journal PLOS Genetics show—fruit fly behavior, in particular the way in which different fruit fly species communicate with one another when their offspring are threatened, is far more complex than was previously thought.

“We knew from past experiments in the lab that when fruit flies within a given species are exposed to parasitoid wasps—which deposit their eggs into and kill the larvae of fruit flies—they will decrease their egg production to protect their offspring,” explains Balint Kacsoh, a PhD candidate in the Bosco Lab at the Geisel School of Medicine, who served as lead author on the study. “They can also communicate that threat, using wing movements, to naïve flies who will then lay fewer eggs, even though they’ve never been exposed to wasps.”

In the new study, the Dartmouth team sought to determine whether different species of fruit flies could communicate in the same way. They found that flies with previous wasp exposure could communicate the threat to their distant relatives, though not as effectively as with members of their own species. However, this interspecies communication was enhanced when flies of different species lived together—remarkably, communal living allowed the flies to learn each other’s “dialects” through the sharing of different visual and scent cues.

“That really surprised us, that an insect that we think is so simple and whose behavior is mostly thought of as being hard-wired, has this complicated repertoire of language, and that socialization has such a big impact on its ability to learn and interpret cues in its environment,” says Kacsoh.

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“We’re really excited about the discovery that Balint, and his lab partner Julianna (Lita) Bozler, have made—it’s showing us a whole new aspect of fruit fly biology and behavior that no one has really appreciated before,” says Giovanni Bosco, PhD, a professor of molecular and systems biology at Geisel, who heads up the Bosco Lab. “With our ability to manipulate fruit flies at the genetic level, we now have a window of opportunity to try and understand the details of how social behavior develops, and to gain new insights into diseases like autism.”

Importantly, says Bosco, the discovery came as a result of the team’s willingness to take a different approach, which was risky. “Everybody who studies fruit flies usually grows them as a single species in the lab,” he explains. “By mixing species together, they were able to observe and test the flies within the context of their natural environment, as we might normally see them in our kitchens and our compost piles.”

“The nice thing about working in Gio’s lab is that he’s very supportive, and he lets us follow these ideas,” says Kacsoh, “and the science is what really drives us to figure out what the best answer is.”

The team plans to build on their work by shedding light on the neural circuitry that controls dialect learning. “So far, we’ve found a number of different clusters—including the optic lobes for visual cues, the olfactory processing centers, and the learning and memory center—that are very important in the dialect learning process,” Kacsoh. “We’re excited to see where that takes us.”

“I think this important research project beautifully illustrates the Dartmouth paradigm, where research is driven by students working closely with faculty on cutting-edge problems,” says Dean Madden, PhD, professor of biochemistry and cell biology and vice provost for research at Geisel. “Learning by doing—that’s how students become discoverers.”