Asynchronous spawning and aggregative behavior in the sea urchin Diadema antillarum (Philippi)

Abstract

This study investigated spawning synchrony and aggregative behavior in Diadema antillarum over the lunar cycle. Urchins spawned on 25 days out of the 29 day lunar month, indicating that spawning is not highly synchronized. When urchins were seen to spawn spontaneously only 5% did so at one time. Slight aggregative behavior occurred throughout the entire lunar month, and did not change significantly over time. The data indicate that contrary to expectations, spawning is sporadic and occurs at low local density. This suggests that fertilization success is poor at the present time and may partially explain poor recruitment seen since the 1983 mass mortality of Diadema.