. Gamete collection
The abalone were induced to spawn by raising the seawater temperature by 2–3 °C for about 2 h before the ultraviolet (UV) light connected to the water supply system was turned on. Immediately upon commencement of spawning the water supply to the tank was changed from UV irradiated seawater to 1 μm filtered seawater of the same temperature. To collect concentrated sperm the water supply to the tank of male abalone was turned off when spawning peaked; approximately 20 to 30 min after the commencement of spawning. The tank was then emptied and the abalone were left undisturbed in the tank for sperm collection. If abalone dislodged from the tank walls, they were dried with paper towelling and put on a rack with their shell facing down. Sperm was underneath each abalone. Sperm collected from abalone that spawned earlier was stored in a refrigerator (4 °C) until the sperm from 3–5 individuals had been separately collected. Sperm samples of the same volume were then pooled from each male used. The time interval from when the sperm from the first male was collected to when the pooled sperm was used in the subsequent experiments was kept as short as possible and never longer than 2 h. Three sperm pools were established in each experiment using sperm from different males. The sperm concentration was standardized to 5.0 × 108 mL− 1 (unless otherwise specified) after being counted under a light microscope with a hemacytometer. Sperm pools with initial motility above 80% were used in the subsequent experiments.
Eggs from at least three females were gently poured into a sieve set with a 300-μm sieve at the top to remove the large debris and a 90-μm sieve partly immersed in filtered seawater below to retain the eggs. They were gently rinsed and washed into a 250-mL settlement beaker. After 10 to 15 min the density of eggs on the bottom of the beaker was estimated and was approximately 25,000 mL− 1.