Moorea: The Coral Reef Community 

From the researcher's perspective...

The idea that crabs may be able to defend their host corals from predators has been around for some time. That said, there have always been lingering doubts; how could such a little crab—about the size of two thumbnails—chase off something as large and scary as a Crown-of-Thorns seastar? And not just one seastar, but many; because when there's an outbreak of seastars, they frequently come in huge numbers.

When the most recent Crown-of-Thorns population outbreak was underway on the island of Moorea, French Polynesia, an interesting pattern emerged—as many corals were consumed by these voracious predators, the ones that survived belonged to a single species, Pocillopora eydouxi. What made this coral different from all the rest was the presence of the largest species of Trapeziid crab, Trapezia flavopunctata. It was a shocking display of how little things can make a big difference, and how important symbioses are in reef systems.

Chris Meyer, Seabird McKeon, Hannah Stewart, and Matthew Johnson