The distribution of mitochondria in oocytes after 40–44 h in culture (0 h group) and staining with the mitochondrial dye, MitoTracker® Red 580. A. Mitochondria surrounding the nucleus (GV) in a freshly-retrieved oocyte. B. Oocyte still arrested at GVBD with mitochondria evenly distributed in cytoplasm. C. Oocyte at MII with mitochondria congregated around the region of spindle and in cytoplasm. Magnification bar in (C) = 50 μm.