Jaws' Grandpa

Not Geography Geography Post 17

The Oldest Vertebrate In The World: The Greenland Shark

I must confess, I have been struggling with inspo for these posts for the last few weeks, but this week I actually had two potential ideas (two!). The topic I've picked was inspired by international fishing aficionado and angling superman, Jeremy Wade of 'River Monsters' - a big personal fave, would 10/10 recommend if you want to see a whole host of ungodly water creatures that will scare you into never entering so much as a stream again. In the particular episode I saw yesterday, Jeremy was looking for the Loch Ness Monster (PSO: all the sightings are just wood, all of 'em), but somehow then ended up fishing for something much more exciting that actually exists - the Greenland shark. It is this monstrosity that will be discussed this week! 

I Have Never Heard of a Greenland Shark?

Unless you have a habit of diving several thousand feet down into the dark and frigid waters of the arctic, or are a viking, then I can't blame you for not knowing the Greenland shark. And maybe after this post, you won't really want to get to know one. 

Greenland sharks have been knocking around in the waters of the Arctic, North Atlantic and North Sea for centuries and inspired some of the Viking sea monster legends, albeit with a bit of Norse Photoshop. During this time, they were avidly fished for and turned into a traditional Icelandic delicacy (?!) called Skalugsuak, which involved drying the bits of shark out for months into a fish jerky kinda thing, because the meat contains unusually high amount of urea/ammonia which make it toxic when fresh. Sounds like something Heston Blumenthal would love. And apparently other people - presumably possessed by the devil - also loved it to the point of almost wiping the species out via overfishing prior to WWII. 

Despite its dubious popularity in the Northern reaches of the world, most people and the scientific community were largely unaware of the Greenland shark until relatively recently. 

What Is So Special About It?

Other than being outstandingly unappetising, the Greenland shark has turned out to be one of the most fascinating fish in the sea. They inhabit waters more Northerly and cold than any other shark, have been found at incredible depths (+8000ft), and because of those two things are mostly blind. They are also second in size only to the great white, so can grow up to 16ft long. They eat mainly fish (no prizes for guessing that), but have also been found with bits of polar bear, deer and reindeer in their stomachs. 

Then there is the small matter of them being the longest living vertebrate ever discovered by science; which is why we are really here. Alongside their impressive size, researchers also noted how slowly the sharks grow - 1cm a year or even less, which makes my complaining about how I haven't grown since I was 13 seem frankly petty. Logic then indicates that for them to grow to the sizes they are being found at would require them to be up to 500 years old! To test the theory, samples of individuals eye lenses were carbon dated, as they do not renew from birth, and confirmed that the average Greenland shark has a lifespan of 392 ± 120 years, and they do not even reach mating maturity until they are 150 (a very similar age to which some men reach mental maturity...)!  

For context then, the oldest shark caught by researchers was estimated to have been born around 1501. That means she was knocking around when Henry VIII was still lopping his wifes' heads off, was over 100 years old when colonists first settled in North America, and was a pup when Da Vinci was still alive inspiring Dan Brown novels. 

Cold = Old?

Currently, scientists are not entirely sure why the Greenland shark lives to the ages that it does, although they have noted that it does everything incredibly slowly, potentially to save energy. I was going to make a joke about the Queen living so long here, but I think that might be treason? 

There may also be a link to their habitat which explains their amazing longevity, because other arctic species also hold records in that department. The Bowhead whale was the previous holder of the oldest vertebrate record at 211 years, and the oldest invertebrate was Ming the Quahog Clam. 

*Side note: Ming the Quahog Clam's story is ironic in that it literally could be something from Family Guy (set in Quahog), because whilst being the oldest living invertebrate ever found at 507 years old, to ascertain it's age scientists actually opened it, which then killed the clam... 

And so, even though the Greenland shark is pretty monstrous, and you probably wouldn't want to meet one alive or dead by the sounds of it, they could offer valuable insights into the study of longevity with habitat and biology. Also v interesting if nothing else!

Hope you enjoyed this week's post, I actually enjoyed writing it too! Have a great week and don't go opening any clams of indiscriminate age just in case!