Researchers have found that sea stars, a type of starfish, have compound eyes at the ends of their legs, though they aren't powerful and their vision is limited to about 13 feet.
Drs. Anders Garm and Dan-Eric Nilsson believe that sea stars use their eyes to navigate the coral reef, a phenomenon which hasn't been observed until now.
The researchers placed sea stars in a tank at 1, 2, and 4 meters from corals. The seas stars placed closer than four meters were able to quickly return to the reef.
Those farther than 4 meters were observed moving randomly in all directions. To test this, they poked out the eyes of sea stars and placed them closer to the coral. They, too, moved about randomly in all directions, unable to find their way back.
The findings of the study have been published January 8 in the journal Proceedings of the Royal Society B.
Unlike the compound eyes of insects, the sea stars' eyes don't have lenses, and don't detect colors or quick movements. As such, it's unlikely they're used for finding food or escaping predators, but instead for navigation.
Unlike the primitive eyes found on flatworms, which can only sense light, a sea star's eyes are developed enough to be able to form an image and discern large objects. Sea stars, like many starfish, are known to re-grow severed arms, meaning they also have the ability to regenerate their eyes.
[Proceedings of the Royal Society B]