SYDNEY Ancient light-sensitive genes may be the
trigger for the annual mass spawning of corals shortly after a
full moon on the Great Barrier Reef, according to a study by
Australian and Israeli scientists.
The cryptochromes genes occur in corals, insects, fish and
mammals -- including humans -- and are primitive light-sensing
pigment mechanisms which predate the evolution of eyes.
The Cry2 gene, stimulated by the faint blue light of the
full moon, appears to play a central role in triggering the
mass synchronized coral spawning, said the scientists in a
paper published in the international journal Science on Friday.
"This is the key to one of the central mysteries of coral
reefs," said Professor Ove Hoegh-Guldberg, who lead the
University of Queensland laboratory which discovered the genes.
"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," Hoegh-Guldberg said in a statement.
The annual mass spawning of corals occurs across a third of
a million square kilometers of Australia's Great Barrier Reef,
shortly after a full moon.
Exposing corals to different colors and intensities of
light and sampling live corals on reefs around the time of the
full moon, Israeli researcher Oren Levy found the Cry2 gene at
its most active in Acropora corals during full moon nights.
The genes developed in primitive life forms in the
Precambrian, more than 500 million years ago, as a way of
sensing light to synchronies their body clocks and breeding
cycles, said the researchers.
"They are, in a sense, the functional forerunners of eyes,"
Cryptochromes still tune humans to the rhythms of the
planet, he said, but had lost their light-sensing function.
"They play important roles in regulating the body-clocks of
many species, from corals to fruit flies, to zebra fish and
mice," said David Miller from Australia's James Cook