Air pollution may hinder the reproduction of insects and drastically lead to population decline
Fruit flies reproduce through sexual reproduction, which involves the fusion of gametes from male and female fruit flies. Female fruit flies select their mates through the scent of their pheromones. Mating typically involves a brief courtship ritual. The male attempts to convince the female to mate by performing a series of behaviours such as wing vibration, leg tapping, and genital licking. Once the male has successfully mated with the female, he deposits a package of sperm, called a spermatophore, into the female's reproductive tract. After mating, the female fruit fly begins laying eggs on suitable food sources, such as rotting fruit or vegetables. She can lay up to 500 eggs during her lifetime, with each egg developing into a larva that undergoes several moults before pupating and eventually emerging as an adult fruit fly.
Environmental factors, such as temperature, humidity, and nutrient availability, highly influence the reproductive cycle of fruit flies. A recent study published in the journal Nature Communications led by Markus Knader, a researcher of evolutionary neuroethology at the Max Plank Institute, shows that ozone pollution can disrupt the male's ability to emit their characteristic odour (pheromones) therefore posing a threat to how successfully fruit flies and other insects reproduce. Scientists tested nine species of Drosophila fruit flies by exposing half the males from each species to ambient air and half to an atmosphere with ozone levels at 100 parts per billion. Average industrial ozone levels are roughly 40 parts per billion, but regions like India, China or Mexico experience magnitudes as high as 210 parts per billion. They found the males exposed to higher ozone levels started emitting fewer pheromones. As a result, they had trouble attracting female partners. Insect pheromones are based on chains of molecules latched together by two carbon molecules. Still, ozone can break up these carbon bonds and dissolve the pheromone strings. The effect in nature is likely to be amplified, as ozone is just one of many environmental pollutants that can do this.
It is essential to highlight that in the lab, it does not matter whether the male has to wait one or two minutes longer to mate. Still, in the field, there is a lot of selection pressure. The flies must be efficient, so they must give everything to find the female as soon as possible, copulate and fertilise her eggs before a predator kills them. What fruit flies are experiencing could be happening for several other insects, including moths, ants, or pollinators like bees, who not only mate but also communicate and coordinate their colonies and nests with unique pheromone signatures.
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