muscly foot to attract mates. But the clusterwink snail is the first discovered to use the shell-flashing trick, which seems to have evolved as a form of self-defense.

“The snail produces light when tapped or around animals that might eat it, even while it’s hiding in its shell,” said Dimitiri Deheyn, a marine biologist at the Scripps Oceanographic Institute in San Diego. Deheyn and his colleague describe the bioluminescent trick of the snail, also known as Hinea brasiliana, in an upcoming study in the journal Proceedings of the Royal Society B.

The snail’s glow-in-the-dark-shell trick was noticed by scientists decades ago, but until now, nobody had any idea what chemicals are involved in generating the glow, or how the shell lights amplifies the light.

“Pinning down what particular biomechanism the snails use to glow is going to be important for the biotech industry,” said marine biologist Mark Moline of California Polytechnic State University, who wasn’t involved in the study.

When threatened, fingernail-sized H. brasiliana generates pulses of bioluminescent light from a single spot on its mushy body. The light pulses are variable, lasting as short as 1/50th of a second to as long as a few seconds. But the opaque shell diffuses only the blue-green color of light it generates — and no other color — like a highly selective frosted light bulb.

“I wondered, ‘How is this possible?’ If you put a blue-green laser up to the shell, the whole thing lights up,” Deheyn said.

When Deheyn and his lab hit the shell with other colors of light, there was no glow. The same experiments performed on the shells of a sister species didn’t make its shells glow using any wavelength of light.

“It’s not only the diffusion that’s pronounced, but also the amplification. The opaque shell is specific to one color, which shows a very close co-evolution of the bioluminescence and the shell,” Deheyn said.

Flashing like a light bulb in dark water may seem like a good way to attract predators, but two different evolutionary ideas back it as an effective protective mechanism. Imagine you’re a crab scuttling for some snail food in the dark, Deheyn says, and you find a delicious meal on a rock.

“Suddenly there’s a bright flash that makes you go, ‘what the hell was that?’ It scares you away,” Deheyn said. To back up the scenario, he described a recent experiment in which a brittle starfish’s bioluminescent glow increased the heart rate of crabs and scared them away.

The snail’s flash may attract some animals that would want to eat it. But it could also attract larger predators to eat those animals before they get to the snail.

“Basically, flashing like a light can attract the predator of your predator,” Moline said. He’d also like to know if the glow is also used as a form of communication between snails.

Deheyn is eager to unravel the snail’s light-making mechanism, primarily to see if it’s viable for tagging DNA. Green fluorescent protein genes derived from jellyfish, for example, won their discoverer a 2008 Nobel prize for their role in highlighting genetic activity in experimental animal models.

Until the chemical reaction and the genes responsible are pinned down, however, he’d at least like to show off the snail’s super-fast flashing ability in high-definition video.

“The problem there is that it’s flashing is too fast,” Deheyn said. “We’d need a piece of equipment called an electron-amplified low-light digital camera. It’s high-def and high-speed, but it costs $50,000. It’s a lot of money.”

Images: Courtesy of Dimitri Deheyn. 1) A Hinea brasiliana shell in green laser light, showing the diffusion/glowing effect. 2) The same Hinea brasiliana in normal light.

See Also:

• 7 Glow-in-the-Dark Mushroom Species Discovered
• Glow-in-the-Dark Shark Turned on by Hormones
• Glowing Monkeys Make More Glowing Monkeys the Old-Fashioned Way
• Glowing DNA that Sticks to Cancer Cells

Authors: Dave Mosher

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