Researchers at the Max Planck Institute for Chemical Ecology in Jena (Germany) have discovered an unexpected effect of air pollution on the behavior of flies. High concentrations of ozone, which are recorded especially in cities in summer as a result of industrial emissions, degrade the sexual pheromones produced by males, causing females to lose interest and become much more lazy in their sexual demands. . At the same time, without these chemical signals, males begin to court other males, unable to differentiate the sex of the conspecific in front of them. The result, the researchers warn in 'Nature Communications', may lead to a decline in insects worldwide. Sexual communication in insects depends largely on pheromones, a natural 'perfume' with an unmistakable odor that allows males and females of a species to be attracted to each other and mate. Most insect pheromones are odor molecules that contain carbon-carbon double bonds. But these bonds are easily destroyed by ozone. Researchers already knew that these environmental pollutants degrade floral aromas, making flowers less attractive to pollinators. The question was whether something similar could happen with the 'love' life of insects. To clarify, the team developed an ozone exposure system for the popular fruit fly (Drosophila melanogaster) that can mimic ozone levels in the air. The researchers created a continuous airstream with precisely defined ozone levels. Related News standard No The naked mole rat hides the secret of female fertility until old age Judith de Jorge This rodent is the only mammal that produces eggs throughout its life. In the experiments, the males were exposed to slightly elevated concentrations of ozone. The scientists then measured whether they were still emitting their pheromone. When flies were exposed to 100 ppb (parts per billion, corresponding to a concentration of 10-9) of ozone for two hours, the measured pheromone levels decreased significantly compared to the control group exposed only to ambient air. Male courtship chains Not being able to detect the pheromones of males, females stopped considering them attractive and ignored them. At the same time, males use scent to distinguish females from other males: while their pheromone attracts females, it repels males. During mating, they transfer their pheromone to their partners. Females that smell that pheromone are no longer attractive to other potential conquerors for two hours. With high levels of ozone, the males exhibited erratic behavior and began courting each other. 'We were surprised that even slightly elevated ozone concentrations had such strong effects on fly behavior. We were quite puzzled by the behavior of the males exposed to ozone, who lined up in long courtship chains," the researchers explain. Two males exposed to ozone try to copulate with each other B.Fabián In addition to melanogaster, the scientists also tested males of eight other species of the genus Drosophila. Only in one, Drosophila busckii, male pheromone release was unaffected by ozone, although they were also less successful at mating. Most males of the studied species became sexually interested in other males. Interestingly, a fly, D. suzukii, which is known to lack pheromones but relies on visual cues, was not affected at all by increased ozone levels. Increased hybridization Researchers believe that flies are not the only insects affected by ozone. «Insects and their pheromones have evolved over millions of years. In contrast, the concentration of air pollutants has only increased dramatically since industrialization, so it is unlikely that insect communication systems will be able to adapt to new conditions in a short period of time. The only solution to this dilemma is to immediately reduce pollutants in the atmosphere," warns Bill Hansson, head of the Department of Evolutionary Neuroethology at Max Planck. Researchers now want to study the effects of ozone on a broader range of insects, including moths that often follow plumes of pheromones over long distances. Sex pheromones also serve to distinguish closely related species, so researchers are interested in whether increased ozone has also led to increased rates of hybridization. Chemical communication is not limited to mating. All social insects, such as bees, ants or wasps, use them to identify the members of their colony. It could even affect the social structure of an anthill after its members are exposed to high levels of ozone following a foraging trip. Fewer insects High levels of ozone are not harmful to human health, but researchers remember that the lifestyle of industrialized nations has a very high cost for the environment and the climate, with many indirect effects that we still do not know. MORE INFORMATION news Yes The resurrection of the Concorde era news No The first complete map of the 'wiring' of an insect's brain, a key step in understanding human behavior In addition to the use of insecticides and the decline of habitat, ozone could explain why why the number of insects drops drastically around the world. If chemical communication is disrupted, they cannot reproduce at a sufficient rate. This can also affect many pollinators, such as bees and butterflies. The 80% in our crops needs to be pollinated by insects, which, as the researchers indicate, "makes clear what scale this problem can take in the future, if we do not manage to drastically reduce air pollution."
