Sydney, Oct 19 : Different species of coral on Australia’s Great Barrier Reef spawn at the same time because their genes sense moonlight, say researchers.

These genes, which synchronise spawning over a couple of days each November, are of the same kind that regulates the human body clock, they say.

“They're timing the spawning, it appears, using the cue of the lunar cycle,” said Prof. Ove Hoegh-Guldberg of the University of Queensland.

“The mystery is how they detect moonlight without eyes,” he said.

The researchers identified the presence of cryptochromes in Acropora millepora coral from Australia's Great Barrier Reef. They then studied the effect of moonlight on the expression of two cryptochrome-producing genes, cry1 and cry2.

Corals are highly sensitive to blue light, which plays a role in regulating body clocks throughout the animal kingdom.

Prof. Hoegh-Guldberg said in corals, such regulation occurred via photoreceptor proteins called cryptochromes.

He said cryptochromes were involved in coral spawning, especially since moonlight shifted towards the blue end of the spectrum.

The researchers then found that the cryptochrome genes were being expressed in the right place for sensing moonlight.

“The production of cryptochrome went up with the full moon. They were responding to moonlight. We had a smoking gun. The genes were expressed in the outer layers of the coral which was important because they were in the right spot,” said Prof. Hoegh-Guldberg.

Prof. Hoegh-Guldberg said the cryptochromes were related to molecules that repair damaged DNA, adding that these repair molecules evolved during the Precambrian period when there was no ozone layer and a lot of ultraviolet light.

“In the deep ocean, the molecules would have told organisms when to hide from strong sunlight, and when it was safe to come back to the ocean surface for feeding. Over time, these molecules evolved into different functions which, for example, allow corals respond to moonlight and fruit flies to respond to day length,” ABC Online quoted Prof. Hoegh-Guldberg, as saying.

The study appears in the current issue of the journal Science. (ANI)