Greenland Sharks Live for Centuries
There are many species for which maximum or even average life span is a question mark. This is a combination of too many species and too few researchers, especially when it comes to marine life, and the fact that for some negligibly senescent species there is no good way to measure age. Their vital statistics and biochemistry change so slowly over time that any estimate may be half a life span removed from the reality. This was the case for lobsters until quite recently, for example. In the research noted here, scientists attempt an new method of age estimation for Greenland sharks, another case in which determining the age of individuals - and thus the species life span - is both quite difficult and little worked on:
A large, almost-blind shark that lives in the freezing waters of the North Atlantic and Arctic oceans is officially the world's longest-living vertebrate. The Greenland shark (Somniosus microcephalus) has a lifespan of at least 272 years, and might live as long as 500 years1. That is older than the 211-year lifespan of the bowhead whale (Balaena mysticetus), the previous record-holder in the scientific literature. It also beats the popular - but unconfirmed - tale of a famous female Koi carp called Hanako, who supposedly lived to 226 years old. Marine scientists already knew that the Greenland shark was long-lived. The fish are enormous but grow slowly, suggesting a long lifespan. Adult Greenland sharks have been measured at more than 6 metres long - and researchers think that they could grow even longer. One 1963 study estimated that the species grows at less than 1 centimetre per year. Getting a definitive measure of the shark's age, however, has proved tricky. Conventionally, researchers count layers of calcified tissue that grow on a fish's fin scales or other bony structures - rather like counting tree rings. But Greenland sharks have small, spineless fins, and their vertebrae are too soft for countable layers to be deposited.
To assess age, the team decided to measure levels of radioactive carbon-14 in fibres in the centre of the shark's eye lens. Such measurements reflect levels of radiocarbon in the ocean when the lens was first formed. Measurements of 28 female Greenland sharks, made during surveys in 2010-13, suggested that the largest of them (at 5.02 metres long) must have been between 272 and 512 years old at the time. The shark's longevity probably arises because it expends very little energy, owing to its cold body temperature and enormous size. Not all cold, large species live to such an exceptional age, so it would be intriguing to know whether the shark has any particular quirks or molecular tricks that contribute to its long lifespan. The study also shows that Greenland shark females don't reach sexual maturity until around 150 years old - suggesting that a century of heavy fishing could wipe out the entire species.
Link: http://www.nature.com/news/near-blind-shark-is-world-s-longest-lived-vertebrate-1.20406
Hi !
Love stories/studies like this one, if only there were more of them (of course, there are only so many animals who reach 250+ years, countable
on one's single hand. Let's just hope that rejuvenation therapies will make us, humans, that 1 st animal on the second hand to reach that milestone
of age).
I'm very surprise and also not, there is some pattern here with giant lobsters (160 y), giant bowhead whales (211 y), giant sea galapagos/seychelle turtles
(255 y), not giant A.Islandica clam (528 y) but the Giant Clam N.zibrowii lives 523 y (a cousin of A.Islandica). And now, giant Gröenland Shark (272-512 y, avg. 392 y).
Many of these fish carry the 'giant' size moniker. Of course, a clam compared to a whale = tiny vs huge. Simple vs complex. Clams are relatively simple
in terms of organs and whatnot. Whales and sharks are far closer to us in terms of organs placement/complexion. And what's more, is that, bowhead
whales are mammals like us - very close. Though, Greenland shark is not mammal (class Chondrichthyes), same goes for turtles or lobsters.
Still, it doesn't change the fact that certain mechanisms are conserved in different class of species. Such as IGF developmental growth
''The study also shows that Greenland shark females don't reach sexual maturity until around 150 years old -''
Well that is something...late, late, real late, like you see you later, later, like never.
Or, my favorite one : 'See you later alligator and in a while crocodile'. Should be 'See you later later alligator-wannabe (greenland shark). Like Never.'
The fact that Greenland shark females don't reach sexual maturity until 150 is surprising (wow...sex and puberty is post-poned to extreme limit) but then not so; this animal is so slow growth, it could
be considered 'Dead' inside (like they said with the 1963 study of 1 cm growth per year ultra slow growth). Like a frigid cold blooded animal that has
almost a flat line pulse; no wonder it lives in Groenland where waters are freezing cold. This ultra low temperature coupled with slow growth (probably
there is veryy little feeding going on, it can stay in CR mode for on and on), would allow a possibility for continuous retarded-but constant/non-slowing
growth over the centuries.
A c-14 eye dating method is decent, but it can be wrong/give wild 'estimates-like' that just estimates not true (with contamination from other mordern sources), they should have tried another method of dating aging :
L- to D-amino acid conversion racemization using the eye amino acid residues (it's what was used in whale eyes to determine their real true age).
It's also interesting they say that other cold adapted sharks or whales don't live as long. It's true. It's a bit puzzling.
There really is a genetic 'jackpot' that hits all the right combinations, wether in cold or hot temperature.
This late sexual maturation in mammals is starting to be ultimate decider of lifespan, in mammals only. IGF (and thus CR/mTOR/Glucose/nutrient diet-composition) and endocrinal hormones controling development yet again.
Humans are sexually mature at 9-13 years old (11 avg), they live to be max 122 years old (80-120, 80-100 common, 90 avg).
Bowhead whales are sexually mature at 20 years old, they live to be 211 years old max (100-200, 150 avg).
A perfect double between the timespan to human and bowhead whale sexual maturity, and double lifespan.
(it shares all those same traits).
PS :
In non-mammals:
Greenland sharks are sexually mature at 150 years old, they live to be 400 avg. old (272-512).
A.Islandica are sexually mature at 35 years old, they live to be 528 years old.
Giant Galapagos tortoise are sexually mature at 20-40 years old (avg 30 y), they live to be 150-255 years old (avg. 200 y)
Giant lobsters sexually mature at 5-7 years (6 avg), they live 80-160 years (120 avg).
A.Islandica did not have higher antioxidant capacity, but it did maintain very low ROS (non-rising, in fact it reduces later in life, most likely by improved redox or lowered metabolism meaning weaker electron flow/less ROS produced at the membrane potential) over life time.
Also, the PI (peroxidizability index of A.Islandica's mitochondrial phospholipids is lower, meaning less peroxidative prone, thus less mtDNA damage/
less lipid hydroperoxide formation in the mitochondrial inner membrane from destruction/peroxidation of polyunsaturates). But this is not
so clear with humans who have higher PI in brain but quite low in all other organs (compared to other species).
Bowhead whales may have a special intestinal bacterial conversion going on, the krill that is sifted through its thin fangs (fanon), is - not -
conserved in its blubber and organ mitochondrial phospholipids as polyunsatuares DHA, EPA. The bacterias do a form of hydrogenisation in its gut,
thus transforming the omega-3 krill into a very saturated/monounsaturated and trans-fat saturared lipids (altering the whale PI).
In fact one study in 1970s showed that the lowest DHA and heart rate was in bowhead whale, thus it explains in part why the long lifespan; mitochondrial
phospholipids alter the 'speed' of metabolism, growth, of enzyme kinetics (how fast chemical reaction happen, cold temperature slows chemical reaction) and thus, aging.
One study showed that the heart of A.islandica keeps on beating for 500 years; it means that cardio protection is crucial for long lifespan.
Same with the study in bowhead whale transcriptome that showed that bowhead whale heart is cardiovascularily strong (increased NO production (nitric oxide, to relax arteries and improve blow flow
during long dives in low O2 underwater), had altered insulin response/improved liver and pancreatic insulin control of glucose disposal (IGF/diabetes).
This was also corroborated in giant galapagos tortoise who grow at ultra-slow speed (but become huge still-slow moving behemoths by a 100 years old).
Continuous growth seems a key element. But not necessarily 'body size growth/mass' but developmental growth /cell size which can be uncoupled even if they work in tandem.
It really is a combination of all of that that make them live over 200 years.
For Greenland sharks, there is more mystery, this animal has no reserach done on it. Though, it's normal, they are so rare in the wild Greenland icy frozen waters with icebergs, hiding deep in the abyss pitch black (they live in the darkness or rise to the ice crust with some light), how can you find them apart from a sighting ?
That's also another thing, living in darkness accelerates melatonin production (pineal gland, controlled through brain IGF-R), which melatonin acts on T-Cells, improving immune system/thymus. Natural Melatonin also scavenges hydroperoxides in membranes (very potent) and induces depigmentation (affects tyrosinase and melanin)/creates sleep.
Sleep, torpor by it would increase the 'slowness/slow sleeping-torpid' state; like a continuous in-dark cold-hibernation for Greenland shark.
Other shark studies showed they have regenerative capacities and regenerate all tissues. Thus, we can infeer that power too for Greenland ones.
Why a Great White Shark does not live 272 years is down to 'living-style' (slow cold slow growth living green sharks vs higher temperature waters/stressful 'shark hunt of seals/fish' by great white).
I would wager the same thing is going on, increased glucose disposal (like CR state), improved insulin, low heart rate (near dead), cold blooded circulation, cold kinetics in enzymes, slowed metabolism,
extra-slowed protracted developmental growth (150 years old sexual female maturation), just living in the 'ultra-slow' lane will mitigate damage to nill, thus live 272 years old, just like a long-lived tree of a few centuries.