The Hawaiian sea creature's light is made possible by its own proteins, and also because of a symbiotic relationship the squid has with a bacteria, the light-emitting Vibrio fischeri.

"The squid has the most sophisticated skin in the invertebrate world, if not the whole world," said Roger Hanlon, senior scientist at the Marine Biological Laboratory in Woods Hole, Massachusetts.

Bobtail squid combine silvery reflector plates on the underside of their bodies with the luminescence of bacteria attached to them. This combination works a bit like the fictional children's character Harry Potter's invisibility cloak. It helps camouflage the squid from predatory fish swimming underneath it. It also helps the nocturnal animal search for food.

What do the glow-in-the-dark bacteria get out of the deal? "They get nutrients and a nice place to live happily," said Wendy Crookes, a researcher at the University of Hawaii-Manoa, who's studied squid for more than a decade.

"I thought this system was the coolest thing I'd ever heard of."

Other ocean animals have light reflectors -- best known among them the odd-looking lantern fish and the flashlight fish that live in the darkest depths of the ocean. But the reflective material in other animals is usually made up of crystals.

Scientists say the bobtail squid's lighting mechanism could lead to new reflective materials and a better understanding of bacteria that benefit their hosts.

"For years people have been interested in pathogenic bacteria, the kind that make people sick," said Crookes. "Perhaps a more appropriate question is, what happens to good bacteria? And how does a body or an animal distinguish between the good ones and the bad ones?"

So far, researchers have named the bobtail squid's proteins that make up their reflective plates "reflectins." They've also found an unusual composition of amino acids in the proteins.

But the little squid still holds many mysteries.

"Scientists should look to nature and biology for well-defined answers, especially in fields like optics," Hanlon said.

The latest research from Crookes and her colleagues on the squid's lighting mechanism, and how this natural technology may translate to medical and industrial uses, is detailed this week in the journal "Science."

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