Fig. 1. Sperm-triggered Ca²⁺ waves in A. aspersa. Dechorionated eggs were injected with Fura-2-dextran (10-20 µM final concentration) and fertilized with preactivated sperm. As noted in several other species and previously also in A. aspersa, two phases of Ca²⁺ oscillations are observed, separated by a brief gap. (A) The temporal pattern of all Ca²⁺ oscillations is displayed. (B) The spatial pattern of the first Ca²⁺ wave is displayed. Time in seconds. (C) This Ca²⁺ wave is followed within 30-40 seconds by a visible cortical contraction that produces a surface protrusion termed the contraction pole (CP; arrow). Bar, 50 µm. Time in seconds. (D) All of the second-phase Ca²⁺ waves originate from the CP (arrow). As noted previously, these waves are faster than the initial Ca²⁺ wave and propagate more cortically (McDougall and Sardet, 1995). Time in seconds. Temperature 19°C, n=34 replicates.