Application of the Mesolens for sub-cellular resolution imaging of intact larval and whole adult Drosophila

In a previous paper (McConnell et al., 2016) we showed a new giant lens called the Mesolens and presented performance data and images from whole fixed and intact fluorescently-stained 12.5-day old mouse embryos. Here we show that using the Mesolens we can image an entire Drosophila larva or adult fly in confocal epifluorescence and show sub-cellular detail in all tissues. By taking several hundreds of optical sections through the entire volume of the specimen, we show cells and nuclear details within the gut, brain, salivary glands and reproductive system that normally require dissection for study. Organs are imaged in situ in correct 3D arrangement. Imaginal disks are imaged in mature larvae and it proved possible to image pachytene chromosomes in cells within ovarian follicles in intact female flies. Methods for fixing, staining and clearing are given.