The results of our study indicate that the actin cytoskeleton is important in modulating the Ca release from the InsP3-sensitive stores, both in the cortex andin the inner cytoplasm. Hence, one of the physiological roles of the rearrangement of the actin cytoskeleton during meiotic maturation may be to sensitize the Ca2 release mechanism in preparation for fertilization(Lim et al., 2001: Santella al., 2004; Moccia et al., 2006). Likewise, the actin cytoskeletal changes during meiotic maturation may also be important for the formation the fertilization envelope. Our data showing that the robust exocytosis of cortical granules by massive Ca2+ release can be blocked by the enhancement of the cortical actin network(hyper-structuralization of the cortex) suggests that the timely regulation of the cortical actin cytoskeleton is crucial not only in generating Ca signals, but also in mediating their cytological outcomes(Figs. 7 and 8).