Working on the Great Barrier Reef, researchers at the University of Queensland in Australia have lifted the lid on one of the great marine mysteries of our time - how corals synchronise their spawning and ensure that it takes place on just a few nights of the year and always when there is a full moon.
They found that the genes encode proteins which respond to blue-green light, which fits perfectly because water absorbs red light very strongly. Then, by growing coral samples in tanks with either a normal light-dark cycle to simulate day and night, or by keeping the coral just in the dark for an extended period, the team found that the levels of the genes peaked in the daylight and dropped off in the dark. Next they collected RNA samples from corals on the reef when there was a full moon, and again when there was a new moon (i.e. no moon) and compared the levels of the two genes. Intriguingly at the time of the full moon the levels of one of the genes - cry2 - were much higher, suggesting that this gene is the linchpin which links the coral's behaviour to moonlight and therefore the spawning pattern.