This large dog fish has multiple surprises hidden behind its “living submarine” look, and some of them are literally explosive.

But I’ll start with the two things you may have already heard about it: 1) it can live for centuries, and 2) it can be eaten putrefied.

While a half-millennium birthday might be stretching it, the Greenland shark is purportedly the longest-living vertebrate.

Kicking the bowhead whale off the top spot, the oldest known female probably clocked 392 years, so she was slowly gliding about while Galileo was pointing at the stars and upsetting everyone. How do we know this? The eyes have it, apparently.

You can usually tell a shark’s age by the growth rings in its vertebrae, but being a “soft” shark, the Greenland’s don’t get hard enough. Instead, Nielsen et al.’s 2016 study looked at the proteins in its eye lenses, and using carbon dating, they were able to estimate its age. The extra carbon-14 from all the 1950s nuclear-testing also made a handy timestamp. That’s not the only explosion involved, but I’ll come back to that later.

All told, the Greenland shark might clock up to 512 years. And, due to it growing about 1cm (0.39 inches) per year, a female won’t be ready for love until at least 150. Being slow growing and slow booming can be a problem, especially when humans are harpoon-happy.

And happy we have been, even if fermented shark isn’t exactly top of the menu.

When fresh, the Greenland shark’s flesh is toxic. Somebody somewhere said “don’t worry, just leave it for a few months”, and they were right.

Will you ever look at cheese and pineapple the same way? Photo by Kirk K.

Known as hákarl, it’s an Icelandic delicacy whereby the flesh is cured for several weeks – so not exactly fresh, but not rotten either – and served in small, fragrant portions for any daring gourmands. Norwegian historian Morten Stroksnes described it as “a metallic taste..like atomic waste!”. How apt.

The meat is also fed to sled dogs, but care needs to be taken in both cases, or there’s the risk of falling “shark-drunk” thanks to all the urea (yes) and trimethylamine oxide. But these aren’t to put us off eating it, in fact the extremely long-lived Greenland shark has plenty of other concerns.

Being a cold water fish throws up several problems.

You need to balance the right amount of water in your body, even while it continually escapes via your skin; you need to keep an eye on your salt levels; and you need to keep yourself from freezing.

Fortunately, the Greenland shark’s aforementioned chemical seasoning does the job. The toxic urea keeps its salt levels up, the trimethylamine counteracts the toxic urea, and both of them together help prevent water loss and act as antifreeze.

So it’s full of nasty chemicals, and smells and tastes vile. Why were we hunting it again?

A couple of reasons over the years. In the nineteenth century – brace yourself for this – it was because we could.

From “A history of the fishes of the British Islands”. Biodiversity Heritage Library.

Initially causing a flap as a suspected “great white of the north”, it was thanks to a Captain Scoresby that we realised it was a different species, and what’s more, it didn’t seem especially bothered by the lance. Scoresby himself recounted:

It is so insensible of pain, that though it has been run through the body with a knife and escaped; […] after a while, I have seen it return to banquet again on the whale being butchered, at the very spot where it received its wounds.

In the early 20th century, O. Boje and A.S. Jensen also marvelled at its dull sluggishness and the ease with which you could simply “seize it by the tail”. But there was a reason for a boom in Greenland shark fishing around this time.

To avoid a literal boom in the comfort of your own home, petrol-powered lamps were a no-no, but you could extract “self-running shark oil” by mashing up a frozen one. At the same time, some of the chemicals in said oil could be used to make nitro-glycerine, which came in handy at certain points in the 20th century. We also killed the shark for potentially interfering with halibut and other fisheries. Strangely enough, we’re still not 100% sure if and how it hunts.

After all, there’s one reason for its supposed sluggishness: many Greenland sharks may be partially sighted.

Surprisingly the artist wasn’t.

Of the 1,505 sharks examined near their namesake country, 84% had a copepod parasite attached to both eyes, resembling an odd tassle or branch. (Link here if you’re not too squeamish.) This causes a clouding of the cornea and partial if not full blindness, but as with the temperature, lack of salt, or a spear to the back, the Greenland sharks didn’t seem too bothered.

Theories abound as to the point of the parasites and why they’re so prevalent, veering between lending the shark some bioluminescence in the dark depths, or as lures for potential prey, neither of which have been proven. Greenland sharks chilling in the shallower waters of Canada’s Baffin Bay didn’t seem to have them, however, so another theory is that they migrate to shallower, brackish water to get rid of them. And migrate they do.

Despite moving at a whopping 3kmh (2mph), the Greenland shark can still migrate over 1,000 km (621 miles). In 1995, it was spotted 1,000 metres (3,280 feet) deeper than first thought too, inspecting the 19th century wreck of the SS Central America 2,200 metres (7,217 feet) down. Given its eyesight, it probably wasn’t marvelling at its construction, but with its lifespan, it might have been enjoying a spot of childhood nostalgia. Either way it was on the prowl, which raises the question of what it eats.

Parts of horse, reindeer, polar bear and even a human leg have purportedly been found in the stomach of a Greenland shark.

Seal and squid are on the menu too, which sounds bizarre given how slow and sluggish it supposedly is. Of course, the first thought is that it scavenges from things unfortunate enough to have fallen through the ice, and since even 19th century whalers falling into the sea saw precisely zero casualties, it probably isn’t interested in live and kicking humans. Accounts of people being attacked in kayaks and throwing babies overboard to survive haven’t been more widely reported either, for some reason.

Long-time divers Chris Harvey-Clark and Jeffrey Gallant reported being rushed by some, only for them to swing away at just under a metre, possibly once they realised they weren’t seals. But best not to push our luck. For now, it’s thought it stealthily ambushes its prey using its keen sense of smell and the usual shark electrodetection gear, and for the rest of the time, gorges on most dead things going.

The Inuit have a few stories about it, though.

One explanation for its stench and toxic flesh is because it was born from a urine-soaked rag. A woman used said urine to wash her hair (for antibacterial purposes, apparently) before drying it with a towel and flinging it out to sea, where it then became Skalugsuak, the first Greenland shark.

A far more unpleasant story involves Inuit sea goddess Senda, who became so after her father killed her lover – a bird – and flung her over the side of the boat to drown her, chopping off her fingers when she tried to hold on. They became other sea creatures, and she began a new life at the bottom of the sea, with the Greenland shark living in her urine pot when it wasn’t keeping her company.

Living arrangements aside, a Greenland shark would be an amazing companion. It can cope with pain, blindness, cold water and darkness without a shrug, and would have some incredible stories to tell. It could also teach us to live life at a slower pace.

TLDR

Latin: Somniosus microcephalus

What? Large, slow-moving dog fish from the Arctic and north Atlantic.

Where? Arctic and north Atlantic waters with a maximum recorded depth of 2,200 metres / 7,217 feet.

How big? May reach a maximum of 7.3 metres / 23 feet in length, but it’s usually around 4 metres / 13 feet.

Endangered? Considered Near Threatened due to bycatch, especially as it has a reproductive rate as slow as its life is long.

Probable motto: I live for centuries. Why should I rush?

They sound awesome. Do they need my help at all?

There are no outright conservation drives, but GEERG, Greenland Shark Research, is trying to find out more about it as well as promote awareness and conservation. They cover other sharks and rays in the neighbourhood too.

Just to prove I’m not fibbing:

Carpenter, Kent E. No date. “Somniosus microcephalus (Bloch & Schneider, 1801)“. Fishbase.se.

Carylsue. 2016. “Old ladies of the sea“. National Geographic Education Blog.

Castro, José I. 2011. “The sharks of North America“. Oxford University Press.

Couch, Jonathan. 1868. “A history of the fishes of the British Islands“. Groombridge and Sons.

Davis, Brendal et al. 2013. “The Conservation of the Greenland Shark (Somniosus microcephalus): Setting Scientific, Law, and Policy Coordinates for Avoiding a Species at Risk“, Journal of International Wildlife Law & Policy 16(4):300-330.

Davis, Nicola. 2016. “400-year-old Greenland shark is oldest vertebrate animal“. The Guardian.

Devine, Brynn M. et al. 2018. “First estimates of Greenland shark (Somniosus microcephalus) local abundances in Arctic waters“. Scientific Reports 8 (974).

Handwerk, Brian. 2016. “These Ridiculously Long-Lived Sharks Are Older Than the United States, and Still Living It Up“. Smithsonian Magazine.

Herdendorf, Charles E., and Berra, Tim M. 1995. “A Greenland Shark from the Wreck of the SS Central America at 2,200 Meters“, Transactions of the American Fisheries Society 124(6): 950-953,

Kyne, P.M. et al. 2006. “Somniosus microcephalus The IUCN Red List of Threatened Species” 2006: e.T60213A12321694.

Meet the world’s oldest-living vertebrate, the Greenland Shark“. 2019. Greenland Shark Research (GEERG).

Mills, Patrick. No date. “Somniosus microcephalus“. Animal Diversity Web.

O’Connor, M.R. 2017. “The strange and gruesome story of the Greenland shark, the longest-living vertebrate on Earth“. The New Yorker.

Rafferty, John P. No date. “Greenland shark“. Britannica.com.

Somniosus microcephalus (Bloch & Schneider, 1801)”. No date. Food and Agriculture Organization of the United Nations.

Somniosus microcephalus“. No date. Florida Museum.

Walter, Ryan P. et al. 2017. “Origins of the Greenland shark (Somniosus microcephalus): Impacts of ice‐olation and introgression“, Ecology and Evolution  7(19): 8113–8125.

Wesiberger, Mindy. 2017. “No, Scientists Haven’t Found a 512-Year-Old Greenland Shark“. Live Science.

Worrall, Simon. 2017. “The strange quest to catch a massive Greenland shark“. National Geographic.

Featured image credit: Photo by Hemming1952.