Facts You Should Know About the Greenland Shark
1. They Are Extremely Large – If you are looking for a Greenland shark in the waters around Greenland, it will be helpful to have a good understanding of their physical dimensions. Greenland sharks are among the largest sharks currently in existence, and they are comparable in size to a Great White. They have been observed growing as long as 6.4 meters (21 feet) and as large as 1,000 kg (2,100 lbs), but the typical Greenland shark weighs in 400 kg (880 lbs) and 2.44 to 4.8 meters (18 to 15.7 feet).
2. Their Meat is Poisonous – Shark conservationists and marine biologists spend a lot of time trying to educate people about the importance of leaving these creatures alone. When it comes to the Greenland shark, though, it is imperative to heed this advice for more than just conservation purposes. Greenland shark meat can cause symptoms that are similar to extreme inebriation, and the neurotoxins can be incapacitating to sled dogs. On the other hand, the meat can be prepared in a fermentation process that removes the neurotoxins, and the result is considered a national dish of Iceland. The national dish, known as Hákarl or kæstur hákarl, is prepared by hanging the meat and leaving it to dry for four to five months, thus removing the adverse effects of the neurotoxins.
3. They Do Not Attack Humans – There are some early Inuit legends that claim Greenland sharks are predatory enough to have attacked numerous kayaks. The reality, though, is that there is not one single verified case of predation between Greenland sharks and humans. They are large and strong enough to easily injure or kill a human if they feel threatened, but history has shown them to be non-confrontational.
4. They Are Hard to Spot – It is understandable that people who take an expedition cruise to Greenland may want to see Greenland sharks, but the odds are rather low. This species was not even captured on film for the first time until 1995, and it took 18 more years for anyone to get a video that depicts these sharks in their natural waters.
5. They Are Master Divers – One of the primary reasons that Greenland sharks are spotted so infrequently is their ability to dive to extremely deep depths. Researchers have recorded them going as deep as 2,200 meters (7,218 feet), and they can sometimes be found relaxing on the slopes and continental shelves that sit far underneath the water’s surface.
6. They Will Eat Almost Anything – Vultures are sometimes referred to as nature’s garbage men, and the same could be said of the Greenland shark. Although they can be found eating seals and fish, these sharks are believed to be primarily scavengers that will dine on any flesh. The members of this species do not seem to care if their meals come from something living or dead.
7. Slow and Steady Wins the Race – Perhaps because they will eat almost anything, Greenland sharks never seem to be in any type of hurry. Their average pace of 0.3 meters per second (0.76 MPH) is so slow that they are also known as sleeper sharks. They can increase their speed temporarily for short bursts, but their size helps protect them from capturing the attention of any would-be predators.
8. The Colder the Better – Many people make light of sharks being cold-blooded, but this particular species truly thrive in a cold environment. They prefer to stay in water that ranges from -1 to 10 degrees Celsius (30.2 to 50 degrees Fahrenheit), and they migrate to the coolest part of the water throughout each season. Greenland sharks are the only known shark species that can tolerate the conditions in the Arctic all year long.
Greenland sharks, with a lifespan of up to 392 years, are thought to possess unique longevity genes now being searched for by scientists.
"Together with colleagues in Denmark, Greenland, USA, and China, we are currently sequencing its whole nuclear genome which will help us discover why the Greenland shark not only lives longer than other shark species but other vertebrates."
The team has taken fin clippings from almost 100 Greenland sharks, including some individuals born in the 1750s.
Already the researchers have mapped out all the 16ft shark's mitochondrial DNA - genetic material held in tiny battery-like bodies in cells that supply energy.
Now they are working on DNA from the cell nucleus, which contains the bulk of the animal's genes.
The "long life" genes could shed light on why most vertebrates have such a limited life span, and what determines life expectancy in different species, including humans.
Little is known about the biology and genetics of the Greenland shark, which inhabits deep water in the Atlantic ocean from Canada to Norway and is found off the coast of Scotland.
Prof Praebel added that the sharks were "living time capsules" that could help shed light on human impact on the oceans.
Many were so old they pre-dated the industrial revolution and the introduction of large-scale commercial fishing.
The shark's tissues, bones and DNA could also provide clues about the effects of climate change and pollution over a long time span.
"The longest living vertebrate species on the planet has formed several populations in the Atlantic Ocean," said Prof Praebel, who was speaking at the University of Exeter at a symposium organised by the Fisheries Society of the British Isles.
"This is important to know, so we can develop appropriate conservation actions for this important species."
http://www.mirror.co.uk/science/dna-sharks-can-live-up-10746116
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