Whereas the more familiar, reef-building corals grow atop each other
, mushroom corals--including the jellyfish-eating specimen at right, seen in March 2009--live individually and are among the world's largest coral polyps, growing up to a foot wide (30 centimeters).
The eight- to ten-inch-wide (20- to-25-centimeter-wide) mushroom corals photographed for the new study, published in the December 2009 issue of the journal Coral Reefs,
were found between 7 and 66 feet (2 and 20 meters) deep in the Red Sea.
It's not known how the mushroom corals, which rely mainly on algae in their cells for nourishment, caught the jellyfish. But marine ecologist Jennifer Smith, who was not involved in the research, speculated that the jellies had run into the corals. The corals then used their short stinging tentacles to grab the jellies and pass them to the corals' mouths.
From there, the jelly would be ushered into the coral's "very simple" digestive system, a gastrovascular cavity that breaks down any food--and then back out the way it came. "The mouth," Smith said, "also serves as the anus."
Photograph courtesy Omri Bronstein