How a mushroom coral goes for a walk without legs

Science News
By Susan Milius
FEBRUARY 14, 2025 AT 9:00 AM

A coral walks into a (sand) bar. This may sound like a joke. But new time-lapse photography shows new details of how a squishy, loner coral polyp without legs manages to “walk.”

Instead of banding together to build coral reefs, mushroom corals typically live alone. From the outside, these corals (within the family Fungiidae) look like shaggy round mushroom caps that fell into the ocean.

While “walk” may be too two-legged a word for the gait filmed by coral biologist and microscopist Brett Lewis, the soft body will “pulse and inflate like a jellyfish,” he says. To nudge forward, the coral polyp turns inflations and pulsations into tiny hops, he and his colleagues report January 22 in PLOS One.

“I always found these corals adorable,” says Lewis, of Queensland University of Technology in Brisbane, Australia. Though “if they were bigger, yes, it would be terrifying.”

Their bodies are wrapped by a sticky biofilm that snags unwary little creatures to eat. When a coral senses a catch, the mouth — or several mouths — open to suck the film and doomed prey toward a stomach with an internal bouquet of wormy filaments. The “worms,” covered with stinging and digestive cells, can writhe through portholes to the outside and even punch directly out through body wall. Monstrous inspiration, Lewis says, to “use … in my Dungeons and Dragons.”
https://www.sciencenews.org/article/mushroom-coral-walk-no-legs