For female moths, finding the ideal plant to host their offspring might be as straightforward as listening closely. When plants are low on water, some emit high-pitched clicking sounds that are inaudible to humans. Female moths, with their sensitive hearing, seem to detect these distress signals and avoid such plants, opting instead to lay their eggs on healthier hosts that can better nourish their caterpillars after hatching, according to a study published on November 14 at bioRxiv.org.
The discovery of ultrasonic clicks from thirsty plants was made in 2023 by colleagues of Rya Seltzer, an entomologist at Tel Aviv University. Seltzer and her team hypothesized that moths, which can theoretically hear these high-frequency sounds, might use this information to their advantage when selecting plants for their young. The researchers conducted experiments with fertile female Egyptian cotton leafworm moths (Spodoptera littoralis) in an arena where one side played the sounds of a dehydrated tomato plant, while the other side remained silent. The moths showed a preference for laying their eggs near the speaker emitting the distressed clicks.
However, when actual plants were introduced into the setup, the moths changed their behavior. With a hydrated tomato plant on one side and a thirsty one on the other, the moths preferred the hydrated plant. In another experiment, with a hydrated plant on each side and a speaker playing distressed clicks on one side, the moths laid more eggs on the silent side. The researchers concluded that when moths have access to plants they can see and smell, they can make more informed choices, avoiding stressed plants and selecting healthier hosts.
“Female moths not only recognize these sounds as being made by plants but also connect them to the physiological state of the plants,” Seltzer says. “It’s fascinating to consider how much information exists below the threshold of human hearing.” Notably, these moths had no prior exposure to plants, having been raised entirely in the lab, suggesting that their ability to detect plant clicks is deeply rooted in their genetics.
Björn Thorin Jonsson, a biologist at the University of Graz in Austria, notes that if an acoustic cue is widespread, reliable, and beneficial for selecting better food or more suitable egg-laying sites, it makes sense for moths to use it. Fernando Montealegre-Zapata, a sensory biologist at the University of Lincoln in England, wonders if the plants’ noises could have agricultural applications, such as discouraging moths from laying eggs on healthy plants through the playback of stress cues.
Seltzer believes that this response to plant noises may be common among insects and plants. Many insects have ultrasonic hearing capable of detecting plant clicks. “I believe that this discovery is just the beginning of understanding the acoustic interactions between animals and plants,” she says.
Source link: https://www.sciencenews.org
