Abstract
The olfactory system of male moths is exquisitely sensitive to pheromones emitted by females and transported in the environment by atmospheric turbulence. Moths respond to minute amounts of pheromones, and their behavior is sensitive to the fine-scale structure of turbulent plumes where pheromone concentration is detectible. The signal of pheromone whiffs is qualitatively known to be intermittent, yet quantitative characterization of its statistical properties is lacking. This challenging fluid dynamics problem is also relevant for entomology, neurobiology, and the technological design of olfactory stimulators aimed at reproducing physiological odor signals in well-controlled laboratory conditions. Here, we develop a Lagrangian approach to the transport of pheromones by turbulent flows and exploit it to predict the statistics of odor detection during olfactory searches. The theory yields explicit probability distributions for the intensity and the duration of pheromone detections, as well as their spacing in time. Predictions are favorably tested by using numerical simulations, laboratory experiments, and field data for the atmospheric surface layer. The resulting signal of odor detections lends itself to implementation with state-of-the-art technologies and quantifies the amount and the type of information that male moths can exploit during olfactory searches.
- Received 12 May 2014
DOI:https://doi.org/10.1103/PhysRevX.4.041015
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Published by the American Physical Society
Synopsis
Beating Turbulence to Find a Mate
Published 28 October 2014
A statistical-physics model provides an accurate description of how animals communicate via pheromones in a turbulent atmospheric environment.
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Popular Summary
Sex pheromones are chemicals secreted by animals for the purpose of attracting mates. Female moths emit blends of pheromones, which act as a form of long-range communication, to entice male moths located hundreds of meters away. These pheromones are transported by atmospheric turbulence, which creates strong gradients of concentration. The resulting signal detected by male moths is known to be strongly intermittent and sporadic, yet a quantitative characterization of this signal is still lacking. Such characterization is important since the behavioral response of male moths is sensitive to the structure of the plumes of pheromones subject to distortion caused by atmospheric turbulence. Furthermore, the statistics of stimuli in physiological conditions is crucial to building olfactory stimulators aimed at reproducing those signals in well-controlled laboratory conditions. We investigate the intensity, temporal structure, and chemical composition of the pheromone signal at the receiver’s end.
We develop a theory that predicts the explicit form of the probability distribution of the pheromone concentration as a function of the distance from the source. We also investigate the durations of pheromone detections and their spacing in time. Our work hinges on Lagrangian methods and is based on the analysis of the trajectory of particles transported by the turbulent flow. We successfully test predictions by numerical simulations and experimental data, both in the laboratory and in the field.
Our work quantifies the amount and the type of information that male moths can exploit during olfactory searches and has applications in a variety of fields, including entomology, neurobiology, and technology. Olfactory signals dictate the flight patterns of male moths, shedding light on the neurobiology of how insects communicate. Our results also have potential applications to techniques that inhibit the mating behaviors of invasive pests. We expect that our findings will pave the way for new laboratory experiments using tethered insects.