For the first time, a predatory coral has been captured by the camera while eating a jellyfish almost equal to its size. The event occurred in March 2009 during a dive among the Red Sea reefs located near Eilat in Israel, and the photos has now been published in the journal Coral Reefs.

Israeli researchers Omri Bronstein from Tel Aviv University and Gal Dishon from Bar-Ilan University were conducting a survey on reefs when they spotted a mushroom coral sucking in a moon jellyfish.

“During the survey we were amazed to notice some mushroom corals actively feeding on the moon jellyfish,” says Ada Alamaru, a member of the research team who is doing her PhD in marine biology supervised by Prof Yossi Loya at Tel Aviv University. “We couldn’t believe our eyes when we saw it.”

Corals are predatory animals but most of them feed on tiny plankton, and corals living close to the surface can also obtain energy by forming symbiotic relationships with photosynthesising algae. While it may be possible for plankton eating corals to ingest miniscule embryonic jellyfish, this is the first time anyone has photographed a coral feasting on adult jelly.

“This is definitely unusual. As far as I know no other coral are reported to feed on jellyfish. However, some sea anemones, which are close relatives of corals, are documented feeding on other jelly species,” Alamaru explains.

The coral in question was a mushroom coral belonging to the species Fungia scruposa while the unfortunate jellyfish was an Aurelia aurita – a type of moon jellyfish. Exactly how the coral managed to capture the jellyfish remains a mystery. The area was subjected to a seasonal bloom of jellyfish brought on by nutrient rich ocean currents.

Zoology Prof. Yossi Loya at the Tel Aviv University in Israel has discovered that corals changes sex to survive periods of stress, such as high water temperatures. By observing the behaviour of Japanese sea corals he discovered that stressed female mushroom coral (fungiid coral) change gender to become males, and that male corals are much better at handling stress and fare better at surviving on limited resources. Not all females go through his change but many do and most of the population is therefore male during periods of intense stress.

Yossi Loya says: “We believe, as with orchids and some trees, sex change in corals increases their overall fitness, reinforcing the important role of reproductive plasticity in determining their evolutionary success. One of the evolutionary strategies that some corals use to survive seems to be their ability to change from female to male, As males, they can pass through the bad years, then, when circumstances become more favourable, change back to overt females. Being a female takes more energy, males are less expensive to maintain. They are cheaper in terms of their gonads and the energy needed to maintain their bodies. Having the ability to change gender periodically enables a species to maximize its reproductive effort.”

Loya’s discoveries have been published in the Proceedings of the Royal Society B. The professor hopes that this new knowledge will help coral farmers by allowing them to reproduce the hardy Fungiid corals more effectively.

Loya has been studying coral reefs for more than 35 years and won the prestigious Darwin Medal for a lifetime contribution to the study of coral reefs. He is also involved in coral rehabilitation projects in the Red Sea and is a professor at the Tel Aviv University in Israel.