MEPS 283:191-198 (2004)  -  doi:10.3354/meps283191

ABSTRACT: Water-borne gametes are known to cue mass spawning in externally fertilizing marine invertebrates. In motile animals, such as sea urchins, they might also cue behavior to enhance fertilization success by either (1) increasing movement and thus the number of intraspecific encounters for numerous small-scale events or (2) causing the formation of small-sized aggregations for single spawning events. 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.

KEY WORDS: Lytechinus variegatus · Movement · Behavior · Spawning · Aggregations · Echinoid