Giant Squid: Still a Deep Mystery

The recent unprecedented video footage of a giant squid filmed in its deep ocean habitat has renewed interest in the enormous -- and yet still mysterious -- species.

It's believed that giant squid (genus Architeuthis) can grow up to 55 feet long. The individual captured on video via a small submarine located in the North Pacific Ocean was about 30 feet long and silver and gold in color, marine biologist Edie Widder, who helped to shoot the footage, said. Her colleague Tsunemi Kubodera added that the squid was missing its two longest tentacles.

Cephalopod experts are intrigued by the world record footage.

"It was really thrilling to see the press releases concerning the filming of a living giant squid with a manned submersible," William Gilly, a professor of biology at Stanford University and the Hopkins Marine Station, told Discovery News.

Gilly previously examined a 7-foot-long giant squid that weighed 300 pounds. It was found floating dead in Monterey Bay, Calif.

"It was missing the tentacles and its stomach had been removed through a hole in its body," he said. "Something strange must like to eat those parts, I guess!"

He also noted that the color-changing system, which functions using organelles called chromatophores that contain pigment and reflect light, was present very deep inside the giant squid's body cavity. In smaller species, this system is arranged only on the body's outer surface.

In recent months, researchers have also learned more about giant squid eyes. The diameter of these eyes measures two to three times that of any other animal.

Dan-Eric Nilsson of Lund University determined that giant squid eyes measure 10 inches, making them about the same size as a large dinner plate. Big is optimal for sight in deep-water environments.

"For seeing in dim light, a large eye is better than a small eye, simply because it picks up more light," Nilsson said, explaining that the light isn't from the sun, but rather from bioluminescence emitted by other deep sea species, such as huge and hungry sperm whales.

This bioluminescence, he explained, is "light produced by small gelatinous animals when they are disturbed by the whale moving through the water. It is well known that bioluminescence can reveal submarines at night, and diving sperm whales will become visible for the same reason."

Bioluminescence even played a key role during the recent filming in about 3,000 feet of water near Japan. Widder, Kubodera and their crew used a lure that mimicked the bioluminescent display of jellyfish in order to attract the giant squid's attention.

Despite the footage and other recent research, there are still more questions than answers about giant squid.

Gilly, for example, mentioned that the following questions remain: What are their daily behavior patterns? Do they rise toward the surface at night like many other large oceanic squid, or do they remain deep all the time? How can they tolerate the very low oxygen levels at great depths? How rapidly can they swim? What do they eat, and how do they catch prey with their very long tentacles? How many of them are there in any one place? Do they travel in groups like other squid? If so, do they show group behaviors associated with hunting, mating or defense? How big and old can they get?

"These questions can, at least in theory, be answered by existing technologies, including manned and remotely-operated submersibles for filming," he said.

He added that another important tool could be video and archival electronic tags for filming interactions with other animals, monitoring swimming activity, recording migration patterns, and documenting environmental parameters -- such as temperature, depth, light and oxygen -- as the squid moves up and down in the water column.

Such tags are programmed to release at a certain time, permitting researchers to non-invasively study the collected data. Gilly and his colleagues are using these techniques to monitor large Humboldt squid in the Gulf of California and off the Pacific coast from Baja California to Canada. No one, though, has yet been able to successfully capture and tag a giant squid for release back into its habitat.

Gilly said Kubodera might be the one, in the future, to solve this problem. In the meantime, Gilly plans "to wait until Jan. 27 like everyone else" to see the rare giant squid footage.

Discovery Channel's Monster Squid: The Giant Is Real, premieres on Sunday, Jan. 27 at 10/9c as the season finale of Curiosity.

Giant squid

What has eight arms with hundreds of suckers, eyes the size of grapefruit and a razor-sharp beak? A giant squid! A team of scientists and the Discovery Channel shot footage of this notoriously elusive creature in action. Click ahead for more squidly fun.

Giant squid have captured, and terrified, the seafaring imagination for centuries. This illustration recreates a giant squid observed off Tenerife in November of 1861.

This giant squid was collected by NOAA researchers off the Louisiana coast in the Gulf of Mexico. The largest invertebrate on Earth, the giant squid is just plain big -- the largest ever found was 59 feet (18 meters) long.

The only squid bigger than a giant is the colossal squid. Captain John Bennett examines the world's first intact adult male colossal squid in 2007 in the Ross Sea, near Antarctica. The squid was about 33 feet (10 meters) long. Check out those suckers!

These two female giant squid were found off Luarca, Spain. For an idea of the size of these creatures, note the gloved hand in the upper-left.

Alien autopsy? Nope. It's one of the Luarca squid from the previous slide, undergoing an examination by Spanish scientists.

Here's a giant squid measuring about 28 feet (9 meters), on display at London's Natural History Museum. This creature was caught in March of 2004, at a depth of 722 feet (220 meters), off the Falkland Islands in the South Atlantic.

A cat strolls past a giant squid in January 2005 in Newport Beach, Calif. That winter hundreds of 3- to 4-foot-long (0.9 to 1.2 meter) squid washed up along the Southern California coast. One theory holds that they ran ashore while chasing grunion.

This is another shot of a squid from the Newport Beach, Calif. wash-up. Giant squid eyes look so human because they’re structured much like human eyes are.

It may look big in the photo, but this larval squid is just 0.4 inches (1 centimeter) long and was photographed through a microscope by Russ Hopcroft, of the University of Alaska Fairbanks.

The humboldt, or jumbo, squid is a carnivorous marine invertebrate with a lifespan of only 1-2 years. But it makes hay while the sun shines on its short life: In that time, it can grow to 4 feet (1.2 meters) long.

We may know it better as calamari, the familiar appetizer, but its proper name is common market squid. This adult market squid was photographed off La Jolla Shores Beach in La Jolla, Calif.

This adult jumbo squid was caught near the Channel Islands by a squid jig aboard an NOAA research ship in 2007. Its tentacles are wrapped around the jig that was used to catch it, which worked by attracting the squid to its glowing yellow plastic.

This is a closer look at the 2007 Channel Islands squid. Its telltale large eyes allow the creature to see in the very low light that permeates its deep underwater habitat.

A squid's razor-sharp beak is a merciless weapon against its prey, allowing it to chomp tasty bites out of its victims. Here we see a close-up of a Caribbean reef squid's beak.

Giant squid aren't without enemies. They're a preferred meal for sperm whales. The whale usually wins, but the giant squid doesn't go down without a fight. Scientists know this because of squid sucker markings, like these, found on dead whale skin.