Effects of waterborne gametes on the aggregation behavior of Lytechinus variegatus

This study investigated the ability of water-borne gametes to induce spawning and aggregation behavior in the echinoid Lytechinus variegatus. In the field, 1 individual from each of 40 pairs of urchins was induced to spawn to test whether spawning would be induced in the other urchin. Additionally, 5 urchins were induced to spawn upstream from 20 individuals placed in a group. Thirteen replicates of this experiment were conducted to test whether the larger volume of gametes combined with more urchins would induce spawning. Ripe and nonripe urchins were also videotaped in a 2 m diameter pool with and without sperm in the water (n = 3). All urchins were found to move rapidly (50 cm min-1), although the amount of movement, distance apart, and number and duration of encounters was the same regardless of their reproductive status or the presence/absence of sperm in the water. Urchins never spawned in response to water-borne gametes although most were found to be ripe.