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Neurobiology

Beating a flight path to food

München, 10/10/2017

The waggle dance of the honeybee is a classical paradigm in behavioral biology. LMU neurobiologists have now investigated how the neuronal circuits process and encode the information communicated during the dance.

Foto: stmax113 / fotolia.com

When a honeybee returns to the hive after a successful foraging trip, the insect communicates the location of the food source she has found to her fellow-workers by performing the so-called waggle dance. The scout’s orientation during the dance indicates the direction of the food source, while the duration of the performance itself reflects its distance from the hive, thus enabling her sisters to localize the site she has discovered. A study carried out by LMU neurobiologists Thomas Wachtler and Ajayrama Kumaraswamy now throws new light on how her conspecifics manage to decode the information in the darkness of the hive. In cooperation with colleagues led by Hiroyuki Ai at the University of Fukuoka in Japan, they have examined the role of nerve cells that respond to the vibrations produced by the dancing bee. Their findings, which have now been published in the Journal of Neuroscience, provide insights into the perception and processing of these informational stimuli by the honeybee brain.

During the waggle dance, the air currents generated by the signaling bee’s wing-beats are detected as vibrational pulses by sensory organs on the antennas on either side of their heads. This disposition of their receptors permits the bees to “hear” these vibrations in stereo, allowing them to determine the position and orientation of the sound source from the difference in the arrival times of the signals at each of the paired antennas. In the new study, the authors identified a novel class of neurons (referred to as DL-dSEG-LP neurons) that responds to signals from both antennas. They therefore assume that these nerve cells are responsible for encoding the directional information contained in the interantennal time difference.

“In addition, we analyzed the responses of two other types of neurons in the honeybee’s auditory system. It had previously been shown that these nerve cells react to vibrations impinging on the antennas, but their role in the decoding the waggle dance was unknown,” Wachtler explains. The researchers went on to demonstrate that these neurons communicate with one another, and are capable of computing the duration of the vibration pulses, which encodes the distance from the hive to the food source.

“Based on the experimental not just electrophysiological, but also morphological and immunohistochemical data collected by our Japanese colleagues, we were able to develop a model of the neuronal circuits involved, which allowed us to simulate how these stimuli could represent the duration of the dance,” says Kumaraswamy. “Our simulations are able to reproduce the main features of the experimentally observed impulse patterns. This in turn shows that the neuronal circuit that we reconstructed on the basis of the recorded responses of the nerve cells is in fact plausible.” These neurons are obviously tuned to respond to the vibrations generated during the waggle dance: In simulations based on the circuit model, their response patterns mimicked those seen in live bees only when stimulated with pulse frequencies similar to those produced during the waggle dance. “Our study constitutes an initial step in deciphering the neuronal mechanisms that serve to process the information communicated by the waggle dance,” Wachtler says. “The next question we want to tackle is how these signals are further processed and interpreted in the bee’s brain.”
Journal of Neuroscience 2017