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Close your eyes and try to pick out blue from an assortment of crayons. It might sound impossible, but a roundworm known as Caenorhabditis elegans can do it. Remarkably, the roundworms are so blind they don't have even basic light-sensing systems, but under a series of tests, scientists were able to prove that the little creatures could avoid blue, which happens to be the color of a common toxin that will kill them.
The researchers used a variety of methods to test the worms, including manipulating the color of the toxin and testing with bright light and dim light. "We were able to definitively show that worms aren't sensing the world in grayscale and simply evaluating the levels of brightness and darkness," biologist Dipon Ghosh said in a statement. "They're actually comparing ratios of wavelengths and using that information to make decisions — which was thoroughly unexpected." Previous research on C. elegans has shown that they can sense temperature, and are able to smell, taste, and feel.
Blindness in nature:
- Several animal species are blind from birth, including eyeless shrimp, star-nosed moles, and cave salamanders known as olms.
- There are approximately 36 million blind people in the world, although another 217 million are moderately to severely visually impaired.
- Animals that are born blind include elephants, giant pandas, and cats.