Starfish lack a centralized brain, and are thought to have a dispersed nervous system in which each arm essentially has its own brain. This so-called "decentralized nervous system" could explain why starfish eyes have low spatial and temporal resolution.
"It's not surprising that starfish don't see sharp, detailed images, because that would require much more brain power than they have," Garm said. "From an information processing point of view, it would be a waste of energy if they had much better vision."
Still, the researchers were able to demonstrate that starfish use their visual systems to recognize and navigate toward their habitats, Garm said.
"The eyes will optimize the contrast between the coral reef they live on and the open ocean," he explained. "This means if they are crawling around on the reef and suddenly get displaced, they can see the reef and move back toward it so they don't starve."
Garm and his colleagues tested this hypothesis with navigation experiments with regular starfish and ones that had been blinded.
"When we displaced the starfish from the reef onto a sand flat, the ones who had intact eyes moved straight back, whereas the blinded ones walked at the same pace but in random directions," Garm said.
The researchers are now expanding their research to include 20 different species of starfish, and they suggest these different types of sea stars may have similar visual systems. The scientists also intend to examine features of the starfish's visual system — such as individual photoreceptors — in more detail.
The new findings were published online today (Jan. 7) in the journal Proceedings of the Royal Society B: Biological Sciences.
Original article on LiveScience.
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