Single Objective Light Sheet Microscopy allows high-resolution in vivo brain imaging of Drosophila.
In vivo imaging of dynamic sub-cellular brain structures in Drosophila melanogaster is key to understanding several phenomena in neuroscience. However, a trade-off between spatial resolution, speed, photodamage, and setup complexity limits its implementation. Here, we designed and built a single objective light sheet microscope, customized for in vivo imaging of adult flies and optimized for maximum resolution. Unlike multi-objective light sheet setups, the microscope uses a single objective at the fly head interface, facilitating sample mounting and inspection, and reducing invasiveness. In contrast to two-photon microscopies, the light-sheet configuration with visible excitation offers reduced phototoxicity. We demonstrate in vivo imaging of the membrane, mitochondria, and dense-core vesicles in the axonal projections of small lateral ventral neurons. The achieved resolution was between 380 to 500 nm within a field of view of 70x50x12 m3. This unique combination of easy sample mounting, high resolution, and the low-phototoxicity of light sheet illumination paves the way for new dynamic studies in the brain of living flies.