Total zinc content increases in the oocyte in a follicle stage-specific manner.A, elemental maps of iron, copper, and zinc for single oocytes isolated from primordial, primary, and secondary stage follicles and analyzed by synchrotron-based X-ray fluorescence microscopy. The color scale bar represents the minimum and maximum elemental contents (μg/cm2) of each element. The scale bar represents 10 μm. B, quantification of total atom number of iron, copper, and zinc from the elemental maps, with whole oocyte area as the ROI. C, quantification of elemental concentration in μg/cm2 of iron, copper, and zinc in the oocyte from the elemental maps. D, plots of total zinc atom number (left) and zinc concentration (right) in the oocytes of all three follicle stages against the diameter of the oocytes. Data represent mean values (SD). N = 5 primordial follicle oocytes, 12 primary follicle oocytes, 11 secondary follicle oocytes (A–D). Letters denote statistically significant differences between developmental stages of each element by two-way ANOVA with Tukey’s multiple comparison test (B and C, p < 0.05) (B: Primary to primordial stage total iron Padj = 0.0017, total zinc Padj < 0.0001; Secondary to primary stage total iron Padj <0.0001, copper Padj = 0.0363, zinc Padj < 0.0001) (C: Primary to primordial stage and secondary to primary stage zinc concentration Padj < 0.0001). See Table S2 for corresponding quantification. ROI, region of interest.