Research Seminar: Dr. Basil el Jundi (University of Würzburg)
Dr. Basil el Jundi (University of Würzburg) hosted by Dr Michael Bok
Life Sciences Seminar Room G13/14
Compass Orientation in Ball-Rolling Dung Beetles
Abstract: Despite their tiny brains, many insects are remarkable navigators. Of these, some diurnal (Scarabaeus lamarcki) and nocturnal (S. satyrus) dung beetles have developed a unique orientation behavior to avoid competition for food at the dung pat. They cut off a piece of dung, form it into a ball and roll it away along straight paths. To keep a straight path, both species rely on celestial compass cues such as the sun, the moon or the skylight polarization pattern. However, some celestial compass cues may be more reliable than others and not all of them are available at any given moment in time. This raises the question of how do dung beetles define the relevance of different celestial compass cues and which navigation strategy dung beetles employ to keep track of their rolling direction? Moreover, how are other modalities, such as wind direction, combined with celestial cues to ensure an optimal straight-line orientation performance? To formulate an understanding of the behavioral and neuronal mechanisms behind the dung beetles straight-line orientation, we analyzed the behavior and brain activity. Using an indoor arena we were able to simulate wind and different celestial cues to beetles while rolling. Using intracellular and tetrode recordings, we tested the neural activity of compass neurons in the presence of an artificial sun, moon or skylight polarization pattern and wind stimuli. We found that the cue hierarchy found behaviorally is matched by compass neurons in the brain. All cells responded to simulated celestial cues and to wind stimuli suggesting that both modalities are combined in the same neural substrate in the brain. These neurons seem to form some kind of snapshot of the celestial visual scenery and combine this information with other modalities to generate a robust internal compass that guides dung beetles through the South African savannah.
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