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Colossal Squid Has Glowing "Cloaking Device," Huge Eyes

Dave Hansford in Wellington, New Zealand
for National Geographic News
May 1, 2008
 
A colossal squid being defrosted this week in New Zealand is yielding "astonishing" new discoveries (see photos).

For starters, the giant species has the world's biggest eyes, as well as light-emitting organs that may serve as cloaking devices, scientists say.

As the 1,091-pound (495-kilogram) female gradually unfolded yesterday, she revealed her two 10.6-inch (27-centimeter) eyes (photo), stunning a team of international experts in a lab at Te Papa Tongarewa, New Zealand's national museum.

"They are clearly the largest eyes ever recorded from any animal," said biologist Dan-Eric Nilsson, of the University of Lund in Sweden. "About the size of a soccer ball."

The animal is the largest known specimen of a colossal squid (Mesonychoteuthis hamiltoni)—and the largest captured squid of any species.

A fishing net had accidentally caught the giant in Antarctica's Ross Sea in February 2007. The squid was kept frozen until the scientific team could be assembled. (See a photo of the squid's capture.)

Nilsson, a specialist in animal eyes, said measurements of the squid's pupils would reveal more about the sensitivity of squid eyes.

"That will tell us everything we need to know about how much light they can actually pick up down there. But the massive size indicates the animal is very visual."

One of the eyes was found to be damaged. The team will use only nondestructive methods to examine the other eye, as the creature is destined for permanent display in the Wellington, New Zealand, museum.

(Watch video: "Colossal Squid Eyes Are Biggest" [April 30, 2008].)

"Absolutely Phenomenal"

"[The eyes] are absolutely phenomenal," said biologist Steve O'Shea of the Auckland University of Technology in New Zealand.

"Nobody had ever seen these things before. We put a camera in the water, shone a light on it, and there was a 'eureka' moment—the eye, with this beautiful lens (photo of lenses removed from squid's eyes).

"And underneath those eyes … around the outside, are two rows of beautiful bioluminescent [light emitting] organs."

The small dots of light generated by these organs are all the squid's prey would be able to see of the giant, O'Shea said. Colossal squid are thought to hunt in total darkness at a depth of about 3,300 feet (1,000 meters).

"The prey might well look at [the squid] and think, Well, I can't be bothered with those two tiny little specks of light. And all of a sudden this great big thing lunges in and latches on to it with vicious hooks" (photo of tentacles with swiveling hooks).

The light from the glowing organs, or photophores, might also help conceal squid as they venture near the surface, O'Shea said.

"The body of the animal is translucent, [but] these very large eyes are anything but translucent.

"If you are a predator approaching from below, you've got two silhouettes of the eyes. So those rows of photophores then beam down light of an equivalent intensity to that from above, so the eyes are rendered invisible." O'Shea said.

"It's a very successful cloaking device."

The squid likely eats prey that also glow—potentially a big problem, given the animal's somewhat see-through belly.

"You don't want to fill your stomach up with things that are glowing, because you're sending out a bright signal to all your predators."

However, evolution may have solved that problem.

The inner lining of the squid's mantle—the large covering just above the head (photo of squid's full body)—is filled with dense, dark red pigment, which would block any light from within, O'Shea said.

Colossal Calamari

The size of the squid's beak (photo)—estimated at between 1.6 and 1.7 inches (43 and 45 millimeters)—suggests the giant was not fully grown, O'Shea said.

"We know from beaks recovered from the stomachs of sperm whales that squid grow considerably larger. So although [the new specimen is] very large, it's certainly not the maximum size."

When fully unfolded, the animal is predicted to measure 26.2 feet (8 meters) long.

Though the giant specimen is being handled with kid gloves, squid specialist Tsunemi Kubodera admitted the team had snacked on a smaller colossal squid used in a practice run for the project.

"It's edible, but the texture and smell … [the flesh] contains ammonia, so it's nearly the same taste as giant squid, but it's much more muscular—tougher," said Kubodera of Japan's National Museum of Nature and Science.

"It tastes very bitter," he declared. "Not so good for humans, but sperm whales like the taste very much."

Eric Warrant of Lund University studies deep-sea animals that thrive in darkness.

He said that, as the fishing continues to increase around Antarctica, it is possible more colossal squid will be caught unintentionally.

"It's too early to say whether fishing techniques … are going to impact on the populations of these squid, Warrant said.

"But if it turns out that we get more and more of these squid being caught, I think that would be the time to make a [conservation] policy about them."
 

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