High-speed imaging of light-induced photoreceptor microsaccades in compound eyes

Inside compound eyes, photoreceptors contract to light changes1-3, sharpening retinal images of the moving world in time2. Current methods to measure these so-called photoreceptor microsaccades in living insects are spatially limited and technically challenging1, 2. Here, we present goniometric high-speed deep pseudopupil (GHS-DPP) microscopy to assess how the rhabdomeric insect photoreceptors and their microsaccades are organised across the compound eyes. This method enables non-invasive rhabdomere orientation mapping, whilst their microsaccades can be locally light-activated, revealing the eyes underlying active sampling motifs. By comparing the microsaccades in wild-type Drosophilas open rhabdom eyes4 to spam-mutant eyes, reverted to an ancestral fused rhabdom state5, 6, we show how two different eye types sample light information. These results show different ways how vision converts space into time2, 3, 7-11, and highlight how compound eyes and their active sampling can evolve with insects visual needs.