I wrote that headline when I was a science journalist and the story spread around the world like a rampaging virus. It even reached Mongolia. I know because the staff at the Australian consulate in Ulan Bator took press cuttings and sent me copies.
The headline was misleading but that didn’t dampen people’s interest in orgies, including those of corals. In a recent post, I joked about the leap second and how it affected corals’ biological clocks. I failed to tell you about their sex lives.
That’s what the students were investigating. They were enrolled in a course of marine science at James Cook University in Townsville, which is right next to the Great Barrier Reef.
It’s a great place for tropical marine science and the students’ research was epoch making. Their diligent work led to the discovery that corals’ biological clocks rule their sex lives and are regulated by the moon.
Corals go in for sex orgies. They have no alternative. They are sedentary creatures, confined to coralline structures, so getting together for sexual reproduction is out of the question. Instead of copulating, they produce vast amounts of eggs and sperm and cast them to the currents.
The resulting slicks of coral spawn are so big they can be seen from space. Thirty years ago, when the students got to work, their true nature had not been investigated properly. A general (and mistaken view) was that they were algae.
The students discovered that the corals synchronise their sexual activity using the phases of the moon as a clock. They are so precise in their timekeeping that they hit off within a couple of days of one another. That’s why the slicks are so big.
By doing it at the same time, the tiny animals produce such a vast quantity of spawn that predatory fish can’t possibly devour the lot. Enough of their offspring survive to settle down and form new colonies.
The orgies occur but once a year, towards midsummer, and are over within a few days. If you are not around to see them, you miss out. In the Northern Hemisphere, coral spawning occurs during the university term. That’s why it had not been discovered there. The American marine scientists were in class teaching their students when it occurred. They got the message and took their students out to sea, the following year, and discovered the phenomenon in the Caribbean.