The ozone in the air made them fall in love with the wrong person

Produced by: Science Popularization China

Author: Ji Qiaoqiao (Doctor of Agronomy)

Producer: China Science Expo

Editor's note: In order to decode the latest mysteries of life science, the China Science Popularization Frontier Science Project has launched a series of articles called "New Knowledge of Life" to interpret life phenomena and reveal biological mysteries from a unique perspective. Let us delve into the world of life and explore infinite possibilities.

Under the blue sky and white clouds, the seemingly clean air hides an "invisible killer" - ozone pollution. You may wonder, doesn't ozone protect us from UV damage? This statement is only half right.

Ozone in the stratosphere can absorb part of the ultraviolet radiation in sunlight that is harmful to organisms, while in the near-ground layer of the atmosphere, ozone becomes a pollutant that has adverse effects on the environment and organisms.

A recent study published in Nature Communications shows that ozone is not only harmful to human health, but also disrupts chemical communication between insects through pheromones, thereby affecting their mating behavior.

What are insect pheromones?

Insect pheromones are chemicals that insects release to transmit information, especially during mating behavior. For example, male fruit flies release a pheromone called cis-Vaccenyl Acetate (cVA) to attract females.

Not only does cVA make it easier for females to find them, it can also be passed on to females during mating, making them less attractive to other males. It's like the male "imprinting" himself on the female to ensure he'll be the father of her offspring.

Pheromones influence insect behavior

(Image source: Engl & Kaltenpoth, 2018)

The sources and hazards of ozone pollution

Ozone exists mainly in the upper atmosphere, forming the ozone layer, which protects the Earth from ultraviolet radiation. However, near the surface, ozone is a harmful pollutant. It is formed by nitrogen oxides (NOx) and volatile organic compounds (VOCs) emitted by fossil combustion, transportation and industrial production under the action of sunlight. In recent years, with the development of industrialization and climate change, global ozone levels have risen significantly, causing serious impacts on ecosystems.

Main factors and processes affecting ozone concentration

(Image source: China's Blue Book on Prevention and Control of Atmospheric Ozone Pollution (2020))

Studies have found that ozone can oxidize the carbon-carbon double bonds in insect pheromones, causing these pheromones to degrade. For example, the content of cVA and (Z)−7-Tricosene, which are specific to male fruit flies, will be significantly reduced after exposure to ozone, thus weakening their attractiveness to females and reducing the mating success rate of male fruit flies.

Scientists have found through experiments that even short-term exposure to ozone concentrations of 100 ppb can cause the degradation of fruit fly pheromones, which in turn affects their mating behavior. In the experiment, male fruit flies exposed to ozone showed a longer mating latency, that is, they needed more time to be accepted by females. This is because ozone destroys pheromones, making it difficult for females to recognize and accept these males.

More interestingly, male fruit flies exposed to ozone also showed significantly increased courtship behavior between males. This is because ozone destroys male pheromones, making it difficult for males to distinguish between genders, and thus mistakenly initiate courtship to other males. In the experiment, male fruit flies exposed to ozone even formed a long courtship chain, a behavior usually only seen in fruit flies with genetic mutations.

Ozone disrupts fruit flies' ability to recognize sex

(Image source: Jiang et al., 2023)

The researchers not only studied Drosophila melanogaster, but also conducted similar experiments on nine other fruit fly species and found that the pheromones of eight of them were also degraded by ozone exposure, which in turn affected their mating behavior. Only one fruit fly (D. busckii) was less sensitive to ozone because its pheromone did not contain a carbon-carbon double bond.

Pheromones specific to different Drosophila species and changes in their sexual behavior after exposure to ozone

(Image source: Jiang et al., 2023)

Not only are the pheromones of male and female fruit flies oxidized by ozone, but the pheromones of female fruit flies are also affected. For example, the content of 7,11-Heptacosadiene (7,11-HD) and 7,11-Nonacosadiene (7,11-ND), which are unique to female fruit flies, decreases after exposure to ozone, which means that female fruit flies will also face difficulties in mating because their pheromones cannot be properly transmitted to males.

With the development of industrialization and the increase of pollution, the concentration of ozone has increased significantly, and the pheromone system of insects is facing new challenges. The presence of carbon-carbon double bonds makes pheromones easily oxidized by ozone, thus affecting the mating behavior and population reproduction of insects.

In addition, the chemical communication between plants and pollinating insects will also be affected, and ozone pollution will disrupt the balance of the ecosystem. For example, ozone will degrade the volatile substances released by flowers, making it difficult for pollinating insects to find flowers, thus affecting the pollination and reproduction of plants. These effects are not limited to insects, but will also affect the entire ecosystem through the food chain.

To protect insects and ecosystems, we need to take measures to reduce ozone pollution , including reducing industrial emissions of nitrogen oxides and volatile organic compounds, promoting clean energy, and improving emission standards for transportation. In addition, it is also very important to strengthen environmental monitoring and protection measures and increase research on ozone pollution and its effects.

I hope that through this article, you can better understand the impact of ozone pollution on insects and realize the importance of protecting the environment. Everyone's efforts can bring positive changes to our planet. Let's work together to protect the environment!

References:

1. Jiang NJ, Chang H, Weißflog J, et al. Ozone exposure disrupts insect sexual communication[J]. Nature Communications, 2023, 14(1): 1186.

2.Engl T, Kaltenpoth M. Influence of microbial symbionts on insect pheromones[J]. Natural Product Reports, 2018, 35(5): 386-397.