…just in case you thought the eight arms, hooked tentacles and sharp, keratin-like beak weren’t enough.

Including said tentacles, the colossal squid may reach up to 14 metres (45 feet) long, and weight-wise, it’s the biggest invertebrate in the world.

Confirming the old cliché, “we know more about the surface of the moon than the ocean floor”, we didn’t discover this enormous squid until 1925, when the remains of one were found in a sperm whale stomach. We’ve only seen a few more since then, with the largest hauled up as bycatch off New Zealand in 2007.

We’ve yet to see one alive in the wild. That’s both a good and bad thing.

There’s plenty of evidence of its comings and goings though. Many southern sperm whales are grazed with scars from their hooks, as are 2-metre (6-foot) long Antarctic toothfish. On the other hand, parts of their beaks and tentacles have been retrieved from inside southern elephant seals, Antarctic sleeper sharks and even seabirds, so its relationship with its neighbours isn’t only one way.

But given where it lives, that’s understandable.

The colossal squid ripples about in the mesopelagic and bathypelagic zones of Antarctica’s Southern Ocean, up to 2,000 metres (6,561 feet) down in pitch darkness, and as we know from our friends the abyssal spiderfish and goblin shark, food can be pretty hard to come by. Probably the only thing its sharp suckers and tentacle hooks don’t hurt are its chances at catching prey, but if there’s one consolation, it’s Rosa et al.’s study on its metabolism.

Given its size and weight, they suspect that, rather than chasing down prey in a woosh of arms, tentacles and beak, it probably hangs still in the darkness, waiting for something even more unfortunate to swim by. So while it’s potential nightmare fuel, it wouldn’t be for very long.

But how does it know when to strike?

This might sound both ridiculous and obvious, but sight is very important to a creature that lives in total darkness.

The colossal squid’s eyes, possibly the biggest in nature, are about the size of dinner plates with a diameter of 27 cm (10.6 inches) and pupils of 8-9cm (3-3.5 inches), in order to drink in as much detail as possible. Unlike the smaller giant squid’s, they’re at the front of its head, giving it binocular vision.

If you’d like a picture to haunt your dreams, here you go.

And, as you’re probably wondering from the title, it makes its own torchlight.

There’s a light organ, or photophore, at the very back of each eye, so when the squid focuses in front, between its arms and tentacles, it has enough to see by in order to strike. Bioluminescence is common at these depths, so leaving its lights on won’t give it away.

It probably can’t see in colour or for very long distances, but it can detect large predators like the aforementioned sperm whale. Or, if it’s anything like its relatives, other colossal squid as well.

One theory behind the tentacles and beaks in the stomachs of other animals is that the colossal squid enjoys a spot of cannibalism too.

According to Remeslo et al., it would probably attack the body rather than the arms – so it can avoid the beak – meaning the tentacles and other parts would likely bear the brunt of the assault. That means free food for any spectators, score!

It’s likely it would only go for dying or weakened members of its own species, and the same goes for the aforementioned Antarctic toothfish; most of the colossal squid bycatch has been from them hooking into other fish caught or dead in the nets. The toothfish can put up a good fight, so perhaps they’re just opportunists when they sense an unfortunate specimen.

Then again, in Rosa et al.’s study, it might not be worth the hassle anyway.

If it is indeed a still and cold-blooded ambush predator, the colossal squid probably isn’t that nutritious. For all its imagined wrestling, the sperm whale might not get much of a meal at the end of it, so maybe it’s just for some gladiatorial fun?

Another thing we can’t seem to agree on is its taste.

Researcher V. Laptikovsky, who studied the aftermath of fights between Antarctic toothfish and colossal squid, boiled a piece of tentacle attached to one of the specimens. In one source he is quoted as saying:

It was okay, better than the widely fished jumbo squid. I would say it tasted like a shortfin squid, a bit chewier because of the size.

However, in another, it’s “delicious”. Roper and Jereb also described it as “excellent and flavourful”. If you can apparently make calamari the size of tractor wheels out of it, you might want to make sure people want to eat it first. Or alternatively, how about we don’t try to eat something we only just discovered?

In any case, aside from suggesting the females are larger and that they breed via internal fertilisation, we don’t know much else about the colossal squid. It feeds – and feeds on – a variety of species in the deep dark waters of Antarctica, so it’s in our and their interest for us to find out more about its ecosystem.

Besides, who doesn’t love a good ocean-going horror story?

TLDR

Latin: Mesonychoteuthis hamiltoni

What? Largest squid species in the world.

Where? The Antarctic and Southern Ocean.

How big? Estimates range from 10-14 metres / 32-45 feet long.

Endangered? Well, we know hardly anything about it, but it lives in deep, dark waters out of reach, and in Antarctic protected areas, so it’s probably fine. It’s ranked Least Concern at the moment.

Probable motto: Don’t be too hard on me, I’m a product of my environment.

They sound awesome/terrifying. Do they need any help?

Well considering it lives in deep, inhospitable waters protected by the Antarctic Treaty System, and we can probably count the amount of bycatch with two hands, it seems safe from us for now, or whichever way round you want to look at it.

Just to prove I’m not fibbing:

Barratt, I. & Allcock, L. 2014. “Mesonychoteuthis hamiltoni . The IUCN Red List of Threatened Species” 2014: e.T163170A980001.

“Colossal squid“. No date. Oceana.

“The difference between colossal squid, giant squid, and octopus“. No date. Te Papa, Museum of New Zealand.

“The eyes of the colossal squid“. No date. Te Papa, Museum of New Zealand.

Fox, Stuart. 2010. “Colossal squid is no monster, study finds“. Live Science.

Jha, Alok. 2007. “Fishermen net biggest-ever colossal squid“. The Guardian.

Remeslo, A.V. et al. 2015. “Alien vs. Predator:interactions between the colossal squid (Mesonychoteuthis hamiltoni) and the Antarctic toothfish (Dissostichus mawsoni)“, Journal of Natural History 49(41-42): 2483-2491.

Robson, G.C. 1925. “XXXIX.—On Mesonychoteuthis, a new genus of Œgopsid Cephalopoda“, Annals and Magazine of Natural History 16(9):272-277.

Rosa, Rui et al. 2017. “Biology and ecology of the world’s largest invertebrate, the colossal squid (Mesonychoteuthis hamiltoni): a short review“, Polar Biology DOI: 10.1007/s00300-017-2104-5.

Sarchet, Penny. 2015. “Colossal squid vs huge toothfish – clash of the deep-sea titans“. New Scientist.

Featured image credit: “Colossal squid, Mesonychoteuthis hamiltoni Robson, collected 2008, Ross Sea, Antarctica“. Gift of the Ministry of Fisheries, 2007. CC-BY-NC-ND4.0. Te Papa (M.190318).