Pollution is increasing mating attempts between male flies

Pheromones play a crucial role in the sexual communication of insects, serving as chemical attractants that enable males and females of a species to mate. These pheromones are gender-specific and even slight variations can prevent mating as individuals can only recognize the distinct scent of their own species.

Most insect pheromones are comprised of odor molecules with carbon-carbon double bonds, which are easily destroyed by ozone. Previous research has shown that environmental pollutants such as ozone and nitric oxide can negatively impact floral scents, making them less attractive to pollinators.

Insect sex pheromones vulnerable to ozone degradation

Given that insect sex pheromones are also vulnerable to ozone degradation, the authors of the study sought to investigate whether air pollution affects the ability of males and females to locate and recognize each other during mating.

Markus Knaden, who leads the Odor-guided Behavior Group in the Department of Evolutionary Neuroethology, was one of the study's lead authors.

This study expands upon previous research exploring how exposure to high levels of ozone affects the way insects perceive flower scents.

The researchers focused on nine species of Drosophila fruit flies, dividing the males of each species into two groups: one exposed to ambient air and the other exposed to an atmosphere containing 100 parts per billion of ozone.

While the average industrial ozone levels are around 40 parts per billion, certain regions such as India, China, or Mexico can experience levels as high as 210 parts per billion.

The study found that males exposed to higher levels of ozone emitted fewer pheromones, making it more difficult for them to attract female partners. This also led to an increase in attempted mating between males as emitting pheromones helps fend off competing males.

According to Markus Knaden, the head of the Odor-guided Behavior Group, male flies need to efficiently find and mate with a female in the wild to ensure the survival of their offspring, making the ability to emit pheromones crucial. In the lab, the delay caused by ozone exposure may not matter, but in the wild, it can have significant consequences.

Ozone destroys carbon-carbon double bonds in pheromones

The study found that exposure to slightly elevated levels of ozone led to a significant decrease in pheromone levels emitted by male flies.

During the experiment, male flies were exposed to 100 parts per billion (ppb) of ozone for two hours, resulting in a noticeable reduction in measured pheromone levels compared to a control group that had only been exposed to ambient air.

The researchers tested male flies from nine different species of the Drosophila genus, including the model fly Drosophila melanogaster.

Only one species, Drosophila busckii, was found to have pheromone release unaffected by ozone exposure, likely due to the absence of carbon-carbon double bonds in their compounds, which are less reactive to ozone.

Air pollution contributes to global decline in insect populations

Air pollution is believed to be one of the contributing factors to the global decline in insect populations.

Many insect species rely on pheromones for sexual communication, and these pheromones often contain carbon-carbon double bonds that are easily destroyed by ozone and other air pollutants.

The disruption of these communication systems can lead to decreased mating success and a decline in populations over time.

The effects of air pollution on insects and their chemical communication are being studied by researchers at institutions such as the Max Planck Center next Generation Insect Chemical Ecology, with a focus on preventing the spread of disease vectors and invasive species, as well as protecting insect ecosystem services.

Immediate action to reduce pollutants in the atmosphere is crucial to mitigate these effects on insect populations.

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