Stressed corals can switch from male to female and back again

March 31st, 2009 - 1:07 pm ICT by ANI  

Sydney, March 31 (ANI): A new study has found that stressed mushroom corals can switch from male to female and back again, the first to show that coral can change sex in either direction, all for conserving energy.

According to a report by ABC News, researchers at Tel Aviv University in Israel conducted the study.

Mushroom corals belong to a family called Fungiidae. They are solitary, mobile species that live throughout the Pacific and Indian Oceans.

Mushroom corals are abundant and diverse, but how they reproduce is something scientists haven’t known much about.

“We know in detail the reproductive patterns of more than 500 coral species, but no one reported before on the fact that some coral species may change sex,” said lead author professor Yossi Loya, a zoologist at Tel Aviv University.

“I believe this was quite a big surprise to all coral reef scientists,” he added.

To learn more, Loya and a colleague travelled to a patch reef near Okinawa, Japan. The reef is home to tens of thousands of mushroom corals, representing a dozen species.

In 2004, the researchers collected, weighed, measured, and tagged about 15 individuals from two species. Each coral then got its own aquarium in the lab.

That July, about five days after the full moon, the mushroom corals did what many corals do - simultaneously release sperm and eggs.

In the ocean, these gamete explosions produce larvae that drift off to become new corals. In the lab, the scientists collected the gametes and looked at them under a microscope.

Then, they returned the corals to the sea.

Initial analyses showed that each coral produced either sperm or eggs. Some types of corals are hermaphroditic, with both male and female parts.

But, mushroom corals appeared to be just one or the other.

The researchers repeated the same experiment in 2006 and 2007. The results grew increasingly surprising.

In 2006, about 25 percent of one species and 50 percent of the other had changed sex since they’d been tagged two years earlier.

In 2007, 80 percent of the corals had changed sex from the year before. A quarter of those had reverted back to the sex they had originally been in 2004.

According to Professor Robert van Woesik, a marine biologist at the Florida Institute of Technology, “We never realised in our wildest dreams that these corals can undergo sex changes. This is really exciting.”

The fact that the corals sometimes switch back from female to male, might be a sign that they are in distress and need to conserve resources. (ANI)

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