The world's largest invertebrate remained hidden from humanity until a tantalising glimpse 100 years ago. It would take decades, however, before we finally came face to face with the colossal squid.

Under sombre, mausoleum lighting at the Museum of New Zealand Te Papa Tongarewa rests a monster. Its enormous body lies in a huge glass coffin, thick tentacles trailing beneath a strange, mottled body that once contained two huge staring eyes.

Amongst displays of animals that inhabit the seas around New Zealand, it resembles a creature from another world – reminiscent of the first awestruck description of a Martian by the nameless narrator in H G Wells' The War of the Worlds. The bunches of tentacles beneath a bearlike bulk and a nightmarish beak of a mouth.

But this is no interplanetary visitor, rather something from the inky blackness of our own inner space: a colossal squid. It is the biggest invertebrate on Earth and the rare specimen on display at Te Papa, the shortened Māori name by which the museum is better known, is the first of these mysterious creatures to have been recovered alive – just briefly – in human history.

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For an animal of such enormous size, the colossal squid has an extraordinary ability to keep itself hidden from human eyes. Its discovery was a gradual process, with hints of its existence stretched out over decades. Then – almost exactly 100 years ago – we got our first glimpse of these almost mythical creatures.

To date, no colossal squid has ever been positively identified as being observed in its natural habitat, though there have been some unconfirmed sightings. In June 2024, scientists from an Antarctic expedition made public that they may have filmed one on a camera attached to a polar tourism vessel in 2023. The brief footage shows what may be a juvenile colossal squid in the frigid waters near Antarctica, but the footage is still being scrutinised by fellow scientists. The fact they can't be sure, underlines just what a solitary and enigmatic creature this huge squid is.

Because the animal lives so deep in an ocean only recently visited by modern humanity, the first clues to its existence were the occasional remains found in the bellies of whales that hunt them. Semi-digested fragments hinted at some huge, strange squid whose arms ended in clubs with sharp, gripping hooks and evoked scenes of titanic battles for survival in the ocean depths as they tussled with whales.

Then, in 1981, a Soviet trawler called Eureka caught an enormous squid in its net while fishing in the Ross Sea off Antarctica. The discovery went largely unnoticed until the end of the Cold War a decade later. In the year 2000, Soviet scientist Alexander Remeslo wrote about the incident on The Octopus News Magazine Online forum, giving first-hand testimony on how the animal was captured.

"It was early morning the 3rd of February, 1981, when I was working in Lazarev Sea near Dronning Maud Land, Antarctica," he wrote. "A fellow scientist rushed into my cabin and pushed me in the ribs, shouting: 'Wake up, we caught a giant squid!' With my cameras slung around my neck I ran on deck. There lay a huge reddish-brown squid. None of the crew members, several of them sea dogs who had been wandering all over the seven seas, had previously seen something like this."

Remeslo's account paints an evocative picture: fine snow was falling on the deck of the ship, and the light was so poor that he struggled to take a properly exposed image of the squid, which had been removed from the net and lay lifeless in front of him.

"Burning with impatience to see the results of my photography, I decided to develop the films immediately on board of the vessel, rather than keeping them for developing in a professional laboratory at home," writes Remeslo, now a scientist at the Atlantic Research Institute of Marine Fisheries and Oceanography in Kaliningrad, Russia, in his account. "The quality of the photos taken that day leaves much to be desired. But the most important thing has been done anyway – to document what was most probably the world's first big specimen of the colossal squid (Mesonychoteuthis hamiltoni), which was raised from the depths onto the deck of a vessel and not removed from a sperm whale's stomach!"

A black-and-white image taken by Remeslo and shared alongside his story shows a pair of the Soviet ship's crew crouching next to the dead squid. The creature's two long arms can be seen in the foreground, clenched like fists. According to Remeslo, the squid measured 5.1m (16.7ft), with the mantle alone measuring more than 2m (6.6ft). The squid was described as being a juvenile female, and not yet fully grown.

It would be more than 20 years before another immature colossal squid would be found. This time, in 2003 it attracted worldwide attention. "Super squid surfaces in the Antarctic", wrote BBC News at the time. The squid was found floating dead on the surface in the Ross Sea off Antarctica and was hauled aboard a fishing vessel.

The animal's remains were transported to Wellington, New Zealand's capital, where two scientists – Steve O'Shea and Kat Bolstad of the Auckland University of Technology – reassembled the creature and examined it. It helped turn O'Shea into an internationally recognised authority on giant squids.

"We're sitting there at Te Papa and I've got this bloody enormous thing sitting on a slab," says O'Shea, who now lives in Paris. "It's completely defrosted. I called up a couple of contacts, and I said, 'Look, I've got this colossal squid sitting on a slab here at the department. You want to come and have a look at it?’."

O'Shea was so excited that he hadn't noticed the date: 1 April 2003. Everyone mistook it for an elaborate practical joke. "Nobody took me seriously," he says. "And it wasn't until we sent them a photograph of what we were dealing with on the slab did the press converge on us… my phone didn't stop ringing for a month."

Even for someone like O'Shea, familiar with large cephalopods, the colossal squid was still a dramatic sight. "I'd never seen anything like it before," he says. "I had worked a lot with a fellow called Malcolm Clarke on a number of my documentaries in the past, and he had spent a lifetime studying the stomach contents of sperm whales – and had reported many times their beaks in the stomachs of sperm whales. I........

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