Fluorescent Caenorhabditis elegans worm on black background
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Even without eyes, these roundworms sense light up to 100 times better than humans

Even though they don’t have eyes, the millimeter-long roundworms known as nematodes have seen the light. In 2008, researchers discovered that the worms squirm away from ultraviolet (UV) rays, presumably to avoid lethal doses of the sun’s radiation in the wild. But when scientists traced the nematodes’ light-avoiding behavior, they found the responsible protein was neither an opsin nor a cryptochrome, the only two types of light-sensitive proteins, or photoreceptors, known to exist in animals. Instead, LITE-1 hailed from a family of taste receptor proteins. This meant one of two things: Either LITE-1 could “taste” chemical byproducts such as hydrogen peroxide that were unleashed when UV light hit the animal’s body, or it was an entirely new kind of photoreceptor. If the latter were true, the protein would signal cells shortly after being hit by photons. In a study published today in Cell, researchers put LITE-1 through a gamut of tests to figure out whether it could truly sense, not just taste, light. Not only did they discover that LITE-1 is indeed a new photoreceptor, but they also found that it’s between 10 and 100 times better at detecting UV light than the human eye is at detecting light on the visible spectrum. Mammals don’t express the LITE-1 protein, but the researchers say it’s possible that other taste receptor proteins might have similar UV-sensitive properties. Engineers might one day even be able to use them to create an improved sunscreen that absorbs more harmful UV rays than usual.