Starfish have historically been thought of as simple animals. Since their eyes are also relatively simple and because they lack a brain, it’s been difficult to figure out how or even if they could see.
But new research suggests that the eyes of sea stars—the term scientists prefer, as the invertebrates aren’t actually fish—can form rough images, preventing the animals from wandering too far from home.
“This [ study] represents a significant breakthrough in our understanding of how sea stars perceive the world,” wrote Christopher Mah, a researcher at the Smithsonian’s National Museum of Natural History in Washington, D.C., in an email.
Scientists studied a starfish species found in the tropical Indian and Pacific Oceans, known as the blue sea star (Linckia laevigata), and published their findings online January 7 in the journal Proceedings of the Royal Society B.
Expectations for complexity in these animals have been low because historically, sea stars were viewed as “simple creatures without complicated behavior,” said Mah, who was not involved in the study.
“In fact, behavior and body form have been shown to be remarkably complex [in sea stars],” he explained.
Scientists have known about sea star eyes for about 200 years, but aside from studying their structure, not much research has been done on them, said Anders Garm, a neurobiologist at the University of Copenhagen in Helsingor, Denmark.
Part of the reason is that it’s been hard to get any physiological information out of the eyes until recently, thanks to advances in scientific equipment, he said.
Previous research suggested sea star eyes were sensitive to light, possibly giving the animal an idea of the location of dark and light spots in their dappled underwater world.
Despite the confirmation of sea star sight, the animals won’t be developing reputations for great vision any time soon.
“The image formed in the starfish eye is a very crude image,” says study co-author Garm. “It only has about 200 pixels.”
But it’s enough to enable the blue sea star to recognize large, immovable structures, he said.
This species is tightly tied to coral reefs. If it wandered off to the sandy flats surrounding those reefs, it wouldn’t be able to find food and would eventually starve.
So being able to locate a reef—likely the only big, static object in a starfish’s immediate vicinity—is very important for these animals.
Starfish have compound eyes, like the ones on arthropods such as insects or lobsters, but the resemblance ends there, Garm says.… More:
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