Fruit Flies Display Play-like Behavior for the First Time

In a recent study, scientists at Leipzig University have for the first time demonstrated play-like behavior in flies. They found that fruit flies (Drosophila melanogaster) voluntarily and repeatedly visited a carousel. “Until now, play-like behavior has mainly been described in vertebrates,” says Professor Wolf Huetteroth, who led the study at the Institute of Biology at Leipzig University and recently moved to Northumbria University in Newcastle, England, as an associate professor. He and his colleagues have just published their findings in the journal Current Biology.

The play-like behavior of the flies described by the researchers, involving voluntary passive movements such as swinging, bobbing, sliding or turning, has now been demonstrated in insects for the first time. "This could help us to find out how we humans also develop efficient self-awareness of our bodies," explains Huetteroth, whose study was funded by the German Research Foundation (DFG).

In collaboration with Northumbria University, the researchers conducted a detailed analysis of how the flies interacted with the carousel. While many flies avoided the carousel, others visited it repeatedly and for long periods. When two carousels rotated alternately, the flies even actively followed the stimulation.

The scientists placed a total of 190 individual flies in a carousel arena, a glass dome about one centimetre high, and then filmed them for 3 to 14 days. The positions of the flies in the recordings were then automatically recognised and tracked using special software. Only a fraction of the data generated was included in the study.

Using several carousels, we generated and analysed a total of around seven years of film data."

Dr. Tilman Triphan, first author of the study

This effort was necessary because, unlike most behavioral experiments on flies, the researchers had to rely on the insects' voluntary behavior. There was not enough space under the glass dome for the flies to fly onto the carousel. "However, we were able to distinguish whether the flies had deliberately walked onto the carousel or jumped onto it in an uncoordinated way. This allowed us to show that unplanned visits to the carousel were rather atypical for the playing flies," says co-author Dr Clara H. Ferreira, an assistant Professor at Northumbria University.

According to Huetteroth, the findings will now allow a detailed investigation of the underlying genetic, neuronal and biochemical factors that influence the fruit fly's playful behavior and the benefits this has for playful creatures in general.