Embryos and dissected ovaries were imaged according to a previously described protocol (Dong et al., 2015 (link); Huang et al., 2011 (link)). Embryos were collected overnight at 25°C. Ovaries from adult females several days old were dissected in halocarbon oil (#95). Dechorinated embryos or dissected ovaries were mounted in halocarbon oil on an air-permeable membrane (YSI Membrane Model 5793; YSI) sealed by vacuum grease on a custom-made plastic slide over a 10 × 10–mm cut-through window. After placing the coverslip on top, a membrane at the bottom ensures sufficient air exchange to samples during the imaging session. The slide was then mounted in an air-tight microchamber (custom made) for live imaging under a confocal microscope. Oxygen levels inside the chamber were controlled by flow of either air or custom O2/N2 gas at the rate of ∼1–5 cc/s. Images were captured at room temperature (25°C) on a Leica TCS-NT confocal microscope (PL APO 40× oil objective, NA 1.25) by Leica TCS-NT software; an Olympus FV1000 confocal microscope (40× Uplan FL N oil objective, NA 1.3) by Olympus FV10-ASW software; or a Nikon A1 confocal microscope (Plan Fluo 40′ oil objective, NA 1.3) by NIS-Elements AR software. Images were further processed in ImageJ (National Institutes of Health) and Adobe Photoshop.