Coral Spawning Behavior and Timing

One of the most prominent examples of synchronized behavior in corals is spawning, the enormous reproduction event known as the “spawning event,” where the moon choreographs sex among many coral species at the same night, once a year. The timing of annual coral spawning varies geographically around the earth but is consistent and predictable at each location. Several environmental fac- tors such as sea temperature, salinity, tidal periodicity, and daylength have been suggested as inducers for gametogenesis and spawning in reef-building corals, whereas the actual spawning event appears to be triggered by the level of lunar irra- diance. The repeated episodes, associated with broadcast spawning year after year, is a classic periodic biological rhythm, which is controled by exogenous zeitgebers and by an endogenous biological clock. A key imperative cue is the moon phase and moon- light. Nevertheless, the specifi c cellular mechanisms mediating this annual synchro- nization of behavior by reef-building corals has remained elusive, and the fact that cryptochromes may be involved in this process may suggest a role for the circadian clock in this unique phenomenon. Sexual reproduction is one of the most important processes for the persistence of reefs, yet worldwide reef systems are being rapidly degraded and face a multitude of threats, including global climate change and the anthropogenic stressors of artifi cial light pollution. Keywords