Meet the Shrimp With Ninja Strength and Bullet Speed
So far the cause of the die-off remains a mystery. “We don’t know if it’s something in the water, or something inside the starfish,” says del Sesto. She and her professor, Marta Gomez-Chiarra, are beginning experiments to isolate a possible bacterial or viral pathogen. They’ll also look at whether a rise in seawater temperature, or other environmental changes, may be a factor.
“There was a big increase in sea star numbers about three or four years ago,” says Gomez-Chiarri, “and often when you have a population explosion of any species you end up with a disease outbreak. When there’s not enough food for them all, it causes stress, and the density of animals leads to increased disease transmission.”
She worries that the disease may persist, preventing recovery of the population. “Diseases don’t just completely disappear after a massive die-off,” says Gomez-Chiarri. That matters because starfish are the original keystone species, and their absence can be devastating for the diversity of other coastal species.
The importance of starfish first became evident in the 1960s in a classic experiment by the University of Washington researcher Robert T. Paine. He was studying the rocky world between high and low tides on the Pacific Coast near Seattle, where the food chain typically consists of barnacles, limpets, chitins, anemones, and particularly mussels. The mussels normally wind up concentrated closer to the high tide line, where it’s hard for starfish, the dominant predator, to get at them.
But when Paine removed the starfish from his study area to see what would happen, the mussels soon crept down toward deeper water, crowding out the barnacles and other species. Within a few years, only eight of the 15 original species still lived in that neighborhood. Paine’s study revealed the surprising importance of top predators in keeping an ecological community healthy. He called the starfish he was studying a “keystone species,” because, like the structure of an arch in a building, everything fell apart when that one piece was removed.
What happens to starfish also matters because other research this summer has revealed they are far more interesting creatures than previously thought. Look at the Wikipedia entry for starfish, for instance, and (at least for the moment) you will see that the starfish “does not have the capacity to plan its actions.” But new research from the University of Copenhagen in Denmark suggests that starfish use the eyes at the ends of their arms in essence to hunt. When researcher Anders Garm removed starfish from their feeding grounds on the coral reef and placed them a meter away on the sand, the ones who’d lost their eyes moved randomly. But the ones with their eyes intact headed straight back to the coral reef for dinner.
(The eye at the end of the arm of a sea star. Photo: Anders Garm/Courtesy of University of Lund)
And in a second study, in the Journal of Experimental Biology, British researchers reveal that starfish are in fact well equipped to hunt and kill. Scientists already knew that starfish use chemosensors on their legs to detect prey. When they find a victim, their legs wriggle eagerly all around like a crowd of fingers. Then their arms fold in around the victim, typically a mussel or clam. Now the British co-authors have identified the neuropeptide that causes the starfish to make its stomach come blooming out of its mouth to engulf its prey, turning the fleshy parts into a kind of chowder that it sucks in for sustenance.
Years ago, the essayist Loren Eiseley described the starfish he found on the beach as “the things beaten in the strangling surf…the lost ones, the failures of the world.” But clearly, starfish are the monstrous little winners of the intertidal zone—assuming they can survive this summer’s mysterious killer on the U.S. East Coast.
When starfish attack: