The breakthrough ends an age-old search for the elusive creature and shows for the first time the movements, behavior and natural habitat of the enormous tentacled animal.
Until now, the only information about Architeuthis had been based on dead specimens found either washed ashore or entangled in trawler nets.
The researchers first tracked sperm whales, regular hunters of giant squid, and discovered that the mammals gathered off Japan's Ogasawara Islands, diving to depths of about 3,250 feet, where giant squid are thought to live.
Once they found a likely spot, they dropped a line with a camera, light and data logger on two jigs baited with common squids and freshly ground shrimps as an odor lure. Pictures were taken every 30 seconds.
At 9:15 a.m. on Sept. 30 last year, a 25 foot squid approached the bait.
"The initial attack was captured on camera and shows the two long tentacles wrapped in a ball around the bait. ... The giant squid became snagged on the jig," Kubodera and Mori wrote.
According to the researchers, the squid's most dramatic characteristic was "the pair of extremely long tentacles, distinct from the eight shorter arms."
After struggling for four hours to free itself from the hooks used to carry the bait, the squid broke away, leaving behind an 18-foot piece of tentacle.
The tentacle was still functioning once on the surface, with "the large suckers of the tentacle club repeatedly gripping the boat deck and any offered fingers," the researchers said.
DNA tests from the severed tentacle matched fragments taken from the remains of other giant squid found around Japan.
The photographs also show how giant squid move and approach their prey, attacking head on, horizontally rather than from above or below.
"Architeuthis appeared to be a much more active predator than previously suspected, using its elongated feeding tentacles to strike and tangle prey. It appears that the tentacles coil into an irregular ball in much the same way that pythons rapidly envelop their prey," the researchers wrote.
According to squid expert Martin Collins, of the British Antarctic Survey based in Cambridge, England, the pictures finally settle a long debate among researchers.
"There had previously been two schools of thought, one which considered giant squid to be sluggish inactive animals and the other, which considered them to be active predators. This exciting discovery confirms that they are active animals," Collins told Animal Planet News.
Leading authority on giant squids Steve O'Shea, at Auckland University of Technology, New Zealand, cautioned against drawing conclusions about the Architeuthis' behavior.
"I've been spending years studying giant squids and I still believe they are not so very active and aggressive. But there is still a lot to find out.
"Thanks to Kubodera and Mori we will be able to study this animal as never before. It is fantastic that someone has succeed in capturing it on a camera at last," O'Shea told Animal Planet News.
