For the first time, scientists have captured images of a live giant squid--the largest invertebrate in the world--in its natural, deep-sea environment. The digital pictures not only show how Architeuthis attacks its prey, but suggest that the animal is more aggressive than previously thought.

For years, scientists have tried to spy on the colossal squid using different techniques, including observing from remote controlled submarines and strapping cameras to sperm whales, which are known to feed on the giant invertebrates. But they have always come up short. Zoologist Tsunemi Kubodera of the National Science Museum and Kyoichi Mori of the Ogasawara Whale Watching Association, both in Tokyo, Japan, finally triumphed in the deep ocean waters off the coast of the Ogasawara Islands, an archipelago 1,000 kilometers south of Japan.

Between September and December each year, these waters host hungry sperm whales, known to dive to depths between 800 and 1,000 meters by day and between 400 and 500 meters by night. Kubodera and Mori used the depth data to target 23 deployments of a bait line affixed not only with squid and shrimp but with a digital camera, timer, strobe light, depth sensor, data logger and depth-activated switch. The camera faced the bait, snapping photographs every 30 seconds for four to five hours.

The strike came at 9:15 a.m. on September 30, 2004. More than fours hours of footage show the squid attacking the bait from a horizontal position and then using its tentacles to strangle the prey. The action contradicts some theories that suggest giant squids are sluggish and use their tentacles to troll for fish. "The long tentacles are clearly not weak fishing lines dangled below the body," the researchers write in their report, published in the current issue of the Proceedings of the Royal Society B. "It appears that the tentacles coil into an irregular ball in much the same way that pythons rapidly envelop their prey within coils of their body immediately after striking."

The squid became entangled in the bait line and, after struggling to free itself, left behind a 5.5-meter severed tentacle. The team used the appendage to compare the creature's DNA with that of other specimens that have washed up on shore, thereby confirming that the beast they observed was indeed Architeuthis. They were also able to estimate the animal's size at eight meters.

Kubodera and Mori hope that their method will lead to more sightings of and more information on this elusive and still mysterious deep-sea creature.