Methods for Investigating Magnetoreception in Honeybees: Toward Testing the Radical Pair Mechanism

Honey bees (Apis mellifera) serve as a compelling model for studying magnetoreception, as they are able to navigate over distances of up to 10 km, and prior behavioral studies indicate they possess magnetic sensitivity. However, the underlying neural and biochemical mechanisms of magnetoreception remain largely unresolved. This study investigates the intersection of quantum biology and neuroscience by exploring the radical pair mechanism (RPM) as a potential basis for magnetic sensitivity in bees. Since the RPM predicts that magnetic sensing is coupled to the visual system, we combined behavioral conditioning with in vivo brain imaging using both visual and magnetic stimuli. Classical conditioning was done by the proboscis extension response (PER), pairing visual or magnetic cues with sucrose rewards. Concurrently, two-photon calcium imaging targeted the anterior optic tubercle (AOTu), a brain region implicated in chromatic processing and potentially in navigation, to assess neural responses to visual and magnetic stimuli. PER conditioning achieved ∼50% learning success with visual stimulus, whereas magnetic stimulus alone elicited no behavioral response. Imaging in four responsive bees revealed a ∼0.2% fluorescence decrease in the visually stimulated AOTu during magnetic stimulation. These results provide initial evidence that RPM-linked magnetic signals can be detected in higher-order bee brain regions through neural amplification, providing support to the hypothesis of visual magnetic integration. This work offers a novel avenue for future experiments to directly test RPM predictions, including light dependence, polarity independence, and disruption by radiofrequency fields.