At some 4,700 feet beneath the sea, marine scientists filmed a shrimp spew glowing matter, or bioluminescence, from its mouth.

This natural event, which might seem fictional, happened as researchers looked for the elusive giant squid in the Gulf of Mexico. They have yet to spot the massive cephalopods -- first caught on film in 2012 -- but recorded, for likely the first time ever, a deep sea shrimp belching a radiant substance into its lightless world.

The collaborative exploration mission, called "Journey into Midnight," seeks to sleuth out both the giant squid and other little-seen animal life in the ocean's sprawling pelagic zone -- the great realm between the surface and the sea floor.

"It's one of the least studied habitats on the planet," explained marine biologist Nathan Robinson, director of the Cape Eleuthera Institute in the Bahamas.

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Robinson and his team captured footage of the shrimp, seen darting through the frame before belching a puff of bioluminescence, using a flashing lure to attract the animal to the camera.

But the shrimp quickly discovered there was nothing to eat, and reacted defensively after colliding with the lure's case, or housing.

"It actually bumps into the housing and gets startled," said Robinson, from the research vessel R/V Point Sur in the middle of the Gulf of Mexico. "The spew is used as a defensive mechanism."

In the dark oceans, sea creatures will naturally create their own radiant light, or bioluminescence, to fend off predators. The puff of light could be a distraction, allowing the shrimp time to escape, explained Robinson. Or, it could be a "burglar alarm," alerting even bigger predators to come near, and then startling the initial predator away.

In the case of the shrimp, marine ecologists know that these critters have specialized glands in their mouth that excrete glow-inducing enzymes (a substance that sparks a chemical reaction). Ultimately, though the chemical mechanism is still under investigation, these enzymes facilitate a reaction that creates light.

Though Robinson has observed deep sea shrimp secrete the glowing stuff after they've been brought to the surface, "this is the first time that we've been able to see the shrimp spew in its natural habitat."

To spy more unprecedented behavior -- and perhaps the elusive giant squids -- the research team uses a deep sea camera called Medusa, developed with the help of bioluminescence expert Edie Widder, who is also aboard the expedition. The camera only emits a faint red light -- light that's invisible to sea life -- so they aren't scared off by the radiant intrusion.

For "bait," Widder employs a ring of LED lights, designed to mimic a bioluminescent jellyfish. "The shrimp sees the lure and it comes in to investigate," explained Robinson.

Widder, who captured the first-ever footage of the giant squids (which she said can grow some 40-feet in length) is also eager to understand why the deep sea glows as night, as radiant, decomposing particles of "marine snow" drift through the black water.

"I believe a significant portion of the marine snow is bioluminescent," Widder told Mashable last year. "I certainly want to know the answer before I die."

"It's my Moby Dick," she added.

But right now, the mission at hand is giant squids. And whatever else might visit her deep sea camera -- like spewing shrimp.

"We're really starting to get a glimpse of these unique behaviors that we've never seen before in their natural habitat," said Robinson, before getting off the phone to search for giant squids.

（作者：汽车电瓶）