They do not look particularly “sporty” when they lazily circling the fruit basket – but apparently the famous Drosophila flies can also perform amazing flight performances: The tiny animals, known as research models, are remarkable marathon fliers, as shown by release experiments in the Mojave Desert. Hungry Drosophilas can therefore fly 12 to 15 kilometers without interruption, which is six million times their body length. This range now also sheds light on a previous mystery of population genetics in Drosophila, the researchers report.
It is one of the best-studied creatures on earth and everyone knows Drosophila melanogaster – the black-bellied fruit fly – from personal experience: These are the pin-head-sized insects that swarm in the organic waste bin, throw themselves into wine glasses or land unerringly on the fruit salad. Due to its many practical properties, Drosophila has advanced to become one of the most important model animals in science: With its help, researchers have already uncovered many fundamental secrets of developmental biology and genetics.
But despite the many insights into their biology, surprisingly there has been uncertainty about one characteristic that makes Drosophila a fly: its ability to fly. “These insects are the standard laboratory model organism, but they are almost never examined outside of the laboratory, so we had little idea of ​​their natural performance,” says Michael Dickinson of the California Institute of Technology in Pasadena.
Questioning look at flight performance
The current study was also motivated by a paradox that researchers pointed out as early as the 1940s: They found that fly populations that were separated by thousands of kilometers are much more genetically similar than long-haul estimates -Flight abilities of the small insects seemed plausible. Because fruit flies typically only seem to buzz slowly in circles, as they do in our kitchens. So the question arose to what extent they behave differently when they are foraging in the wild. There were tests over 40 years ago that confirmed that Drosophila had a considerable range, but it remained questionable to what extent the wind had helped.
To ensure reliable results on flight performance, Dickinson and his colleagues have now carried out release and recapture experiments in the Mojave Desert, where Drosophila is not normally found. Flies were released and then lured into traps at specified locations in order to record how long it took the insects to fly there. To do this, the team set up ten odor traps in a circular ring, each within a one kilometer radius of the release site. Each trap contained a fragrant cocktail of fermenting apple juice and champagne yeast, tempting for Drosophila. In addition, the researchers set up a weather station to measure the wind speed and direction during the experiments.
About six million body lengths
As the researchers report, after opening the container with the flies in calm conditions, it took about 16 minutes for the first traps to arrive at the traps one kilometer away. As a result, they were traveling at a speed of about one meter per second, say the researchers. As they emphasize, the animals reach correspondingly higher speeds when there is a tail wind. However, the team also interpreted the measured speed when there was no wind as a guideline value that tends to be underestimated – because the flies may have had to orientate themselves after being released or had initially not taken perfectly straight routes to the scent traps.
The researchers then combined their data with the results of previous laboratory tests, according to which fruit flies can stay in the air continuously for up to three hours. Applied to the new results, this means that the insects can travel around 12 to 15 kilometers in a non-stop flight without wind. This distance corresponds to about six million times the average body length of a fruit fly of 2.5 millimeters, emphasize the researchers. In analogy to this, an average person would cover a little more than 10,000 kilometers on a single journey – this corresponds roughly to the distance from the North Pole to the equator. In relation to their body size, the flight performance of the small flies can also compete with that of some migratory bird species, say the scientists.
“The ability of Drosophila melanogaster to spread has so far been greatly underestimated,” said Dickinson, summing up the result. This now sheds light on the natural abilities of these prominent model animals and the previous distribution paradox, say the scientists. However, there are also general indications for the research area of ​​so-called movement ecology, which deals with how animal populations move and spread. The focus is often on invasive species. As the researchers point out, the focus is also on a notorious relative of the fruit fly: Drosophila suzukii, originally from Southeast Asia, is currently spreading around the world and causing damage to fruit growing.
Source: California Institute of Technology, technical article: PNAS, doi: 10.1073 / pnas.2013342118