Dim light navigation: Elucidating the role of bumblebee ocelli from form and physiology to function

Present in the sky but invisible to humans is a pattern of polarised light (PL) that many animals use as a compass cue to navigate.

Previous work suggests that bumblebees use PL to navigate at dusk–when it is too dark to see other cues–and that they do this using their secondary visual system called the ocelli. However, nothing is known about how these tiny eyes support this extraordinary behaviour.

Our main goal is–with 3 work packages (WP)–to fill this knowledge gap by describing the anatomy, physiology and function of bumblebee ocelli.

The results will provide not only the first detailed investigation of bumblebee ocelli but will reveal how PL is used for navigation in dim light.

We will use micro-CT and fluoresence microscopy to describe anatomically, in 3D, how the ocelli sample PL from the sky and transfer this information into the brain (WP1, year 1-3).

Along with two-photon microscopy and multichannel electrode recordings in the ocellar tract, this will provide us with key insights into how and where PL information is combined in the brain (WP2, year 2-4) and–using behavioural experiments–how bumblebees use it when navigating in dim light (WP3, year 1-2).

Our results will not only answer questions central to neuroscience–how are sensory signals combined in the brain and used to generate behaviour?–but will advance our understanding of bumblebee sensory systems and ecology and provide inspiration for engineers designing lightweight autonomous guidance systems.