As any comic book lover knows, when superheroes band together the bad guys fall harder. The strength that comes in numbers is greater than the sum of its parts.
The same holds true, researchers have recently learned, when different species of crabs (genus Trapezia) and snapping shrimp (Alepheus lottini) in the central Pacific band together to defend their coral homes from hungry seastars. In these frequent conflicts "one-plus-one doesn't always equal two, sometime it is more," explains Seabird McKeon, a marine biologist at the National Museum of Natural History's Smithsonian Marine Station in Fort Pierce, Fla.
The crustaceans are much more effective when they fight together than when they fight alone, a process McKeon calls the Multiple Defender Effect.
"It is a clear example of synergy, and one that underscores the importance of biodiversity in the ocean."
Even in a comic book one would be hard pressed to find an enemy more bizarre than the "cushion" seastar (Culcita novaeguineae), an animal used by McKeon in recent laboratory experiments with living corals (genus Pocillopora) and their defenders. To consume a coral, the seastar pushes its stomach outside its body and lays it over the coral like a cushion. It then hugs the coral close and "eats," letting stomach acids and digestive juices do their work.
The stationary coral is defenseless, yet the tiny crustaceans that live among its branches come to its aid, snipping and prodding an intruding seastar with their claws.
"The coral itself is like a cauliflower head, a main central stem and lots of little branches," McKeon explains. "Crabs gain protection from fish by living inside the coral structure."
Once a mating pair of crabs takes up residence on a coral head they do not tolerate the presence of other crabs of their same species. Crabs of other species, however, are ignored, as are snapping shrimp. As a result,
|Contact: Kelly Carnes|