What is the colossal squid? How big is it and where was it found as video footage captured for the first time

It has been almost 100 years since the colossal squid was discovered, but now video footage has been captured that offers a rare insight into one of the ocean's most mysterious animals.

The colossal squid, also known as mesonychoteuthis hamiltoni, holds the title of the largest invertebrate on Earth. It can grow up to 10m long and weigh almost half a tonne. It's also the biggest mollusc and has the largest eyes of any known animal, measuring about 30 centimeters across.

Until now, most of what researchers knew about the squid came from dead specimens - either found in whale stomachs or caught by accident in fishing nets. Its life cycle remains mostly a mystery.

But that changed when researchers aboard the Schmidt Ocean Institute’s vessel Falkor recorded a juvenile squid - about 30 centimeters long - off the South Sandwich Islands in the South Atlantic. The sighting happened on March 9 at a depth of 600m, using the institute’s remotely operated vehicle, SuBastian.

“It’s exciting to see the first in situ footage of a juvenile colossal and humbling to think that they have no idea that humans exist,” said Kat Bolstad, a squid and octopus expert at Auckland University of Technology.

Dr. Bolstad, who confirmed the squid’s identity for the Schmidt Ocean Institute, added: “For 100 years, we have mainly encountered them as prey remains in whale and seabird stomachs and as predators of harvested toothfish.”

Juvenile colossal squids are nearly transparent - a trait they lose as they mature. Another distinguishing feature is the presence of hooks on the center of their eight arms, which sets them apart from their relative, G. glacialis, whose deep-sea debut on camera happened earlier this year near Antarctica.