Early events of fertilization in sea urchin eggs are sensitive to actin-binding organic molecules.

•Cytochalasin B and latrunculin A prolong the latent period at fertilization.•Jasplakinolide and phalloidin attenuate the kinetics of net Ca2+ reuptake.•Ca2+ wave is sufficient for neither sperm entry nor cortical granules exocytosis.•Actin drugs generally inhibit sperm entry, but may induce polyspermy at low doses.•Actin is the major decisive factor for sperm entry and cortical granule exocytosis.