An adult T. danae attacks the large fluorescent spotlights on the researchers’ underwater camera; links to full videos are included in the article (Image: Tsunemi / Proc. Roy. Soc. B)

A large, deep-sea squid has been caught on video for the first time. The footage of the Dana octopus squid shows that far from being sluggish, passive creatures, the bioluminescent creatures are fast, aggressive hunters.

Furthermore, the Japanese researchers who caught the squid on camera think they may have seen it attempt to communicate with the small torches they were dangling along with the bait in front of their underwater camera.

Taningia danae is an eight-armed squid measuring up to 2.3 metres long. It has two large bioluminescent “bulbs”, called photophores, at the end of two of its arms. The researchers filmed adult squid emitting both short and long flashes from their photophores when they attacked the small Japanese common squid that were used as bait.


The team suggests T. danae – which lives between 240 and 940 metres below the surface – might use these flashes to stun or distract their prey when attacking, and also to measure distances. Watch a movie of a squid flashing at its prey before attacking.

Seductive lighting?

The most curious flashing behaviour, however, was triggered by two pencil-shaped underwater torches that were attached to the bait. The researchers noticed that when both torches were lit, adult squid would sometimes wander around the bait without attacking it.

They would produce long glows from both of their photophores as they approached the torches, then several shorter glows as they moved around it. Watch a movie of a squid making flashes at the pencil torches.

The scientists think the squid may have mistaken the pair of torches for another squid and the long and short flashes could have been attempts at communication, or even courtship.

Many species of small and medium-sized squid have bioluminescent spots on their bellies and some have spots under their eyes. These are thought to serve to identify their species, or indicate whether or not they are sexually mature. But T. danae‘s fluorescent bulbs are unusual in being situated at the end of its arms.

Flip around

The researchers were perhaps even more surprised to find that T. danae was an extremely active and aggressive animal. Like many other large squid, its muscles are flabby because of the tiny bubbles of ammonia that give it buoyancy. This has led researchers to suggest that these squid must be sluggish, largely inactive animals.

In fact, the videos shows that adults are extremely agile – they can flip around very suddenly. They can also swim forwards just as easily as they swim backwards, reaching speeds of 9 kilometres per hour, by flapping their large triangular fins. Watch a video of a large squid attacking the underwater camera’s halogen spotlight.

“I was surprised that T. danae could swim very rapidly and freely,” Tsunemi Kubodera at the National Science Museum in Tokyo, Japan, told New Scientist. “I was also impressed by their aggressive hunting behaviour.”

Kubodera was responsible for another squid first in 2005, when he captured the first ever pictures of a live giant squid in its natural habitat.

Videos of other deep-sea squid species can be found here and here.

Journal reference: Proceedings of the Royal Society B: Biological Sciences (DOI: 10.1098/rspb.2006.0236)

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