Encoding a time-compensated sun compass

• Applicant: Professor Dr. Basil El Jundi
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: from 2016 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 317616350

Every year, millions of monarch butterflies migrate over thousands of kilometers from North America to their overwintering habitats in central Mexico. To maintain a constant migratory direction, these butterflies rely on celestial compass cues, such as the sun or the skylight polarization pattern as references. However, using celestial cues as references poses one major problem: While the butterflies aim for a fixed compass direction, the sun and skylight cues change their position over the course of a day. Thus, the migrating animals need to compensate the daily changes in sun position to be able to adjust their flight direction to the corresponding time of day. Behavioral experiments have indeed shown that monarch butterflies use a time-compensated sun compass for orientation and that the corresponding time information is transferred via clock neurons of the antennae into the brain. Where exactly these antennal time signals and the skylight information converge in the brain and how the neural tuning of an internal compass changes according to the changes in sun position is still unknown.In this project, I will investigate the general principles of an internal navigation compass and how time information influences this network. Using behavioral experiments, I will test the relevance of each celestial cue for the migration of butterflies and how the time of day changes this relevance. In a next step, I will analyze the time information pathway from the antennae to the brain and find out, where time information is integrated into the sky compass network. To understand how a time-compensated sun compass is encoded, I will study the neural tuning of descending compass neurons through intracellular recordings and determine how their preferred directions to celestial cues change with the time of day. Finally, I will also test the neural substrate via extracellular multiunit recordings while the fixated butterfly experiences the natural sky, and later while the animal is allowed to freely alter its azimuthal heading in a flight simulator. These pioneering experiments are the first step in understanding how a time-compensated sun compass controls the orientation behavior in a behaving animal in its natural habitat.

• DFG Programme: Independent Junior Research Groups
• Participating Person: Professor Dr. Wolfgang Rössler