A gene for moonlight romance?

A team of Australian and Israeli researchers has possibly discovered the aphrodisiac for the biggest moonlight sex event on the planet.

An ancient light-sensitive gene has been isolated by researchers from the ARC Centre of Excellence for Coral Reef Studies (CoECRS) that appears to act as a trigger for the annual mass spawning of corals across a third of a million square kilometres of Australia’s Great Barrier Reef, shortly after a full moon.

Called cryptochromes, the genes occur in corals, insects, fish and mammals — including humans — and are primitive, light-sensing pigment mechanisms which predate the evolution of eyes.

In a paper published in the international journal Science, the team reports its discovery that the Cry2 gene, stimulated by the faint blue light of the full moon, appears to play a central role in triggering the mass coral spawning event.

“This is the key to one of the central mysteries of coral reefs,” said Prof Ove Hoegh-Guldberg, who leads the University of Queensland (UQ) laboratory in which the genes were discovered.

“We have always wondered how corals without eyes can detect moonlight and get the precise hour of the right couple of days each year to spawn.”

What allows corals to spawn simultaneously along the immense length of the Great Barrier Reef — and also in other parts of the world — has been a scientific mystery till now, though the researchers knew that tide, water temperature and weather conditions played a part. However, the remarkable synchronisation of spawning occurring all along the Reef immediately following a full moon suggested that moonlight was a key factor.

Exposing corals to different colours and intensities of light and sampling live corals on reefs around the time of the full moon, the team found the Cry2 gene at its most active in Acropora corals during full moon nights.

“We think these genes developed in primitive life forms in the Precambrian, more than 500 million years ago, as a way of sensing light,” said Dr Oren Levy of CoECRS and UQ, who headed the research.

“The fact they are linked with the system that repairs damage from ultraviolet (UV) radiation suggests they may evolved in eyeless creatures which needed to avoid high daytime UV by living deep in the water, but still needed to sense the blue light shed by the moon to synchronise their body clocks and breeding cycles.”

“They are, in a sense, the functional forerunners of eyes,” Prof Hoegh-Guldberg said.

He said cryptochromes still operate in humans as part of the circadian system, though their light-sensing function appears lost to us.

Whether they have anything at all to do with human associations between the full moon and romance is unknown.