The Greenland shark is the longest-living vertebrate

When we consider animals with long lifespans, certain species of whales or tortoises come to mind. The Greenland shark, on the other hand, is among the most unexpected candidates to be the longest-living vertebrate. This amazing animal navigates the icy waters of the North Atlantic and the Arctic, bringing with it mysteries of the deep that would astound anyone who discovers them.

According to some estimates, Greenland sharks have a centuries-long lifespan and can live up to 300 years or longer. They differ from the majority of other fish and vertebrates due to their extraordinary longevity. But why is their longevity so remarkable? Scientists think that the combination of these sharks’ distinct biology, chilly environment, and sluggish growth allows them to survive for such a long time.

Greenland sharks are fascinating for other reasons besides their age. They are renowned for leading enigmatic lives and for frequently lurking in places where few people go. Comprehending their life cycle and the surroundings they live in can provide insight into the adaptability of life in harsh circumstances.

A window into the wonders of nature is provided by investigating the world of the Greenland shark. Learning more about these extinct sharks helps us understand not only how they survived but also the larger ecosystems they call home. Come along as we delve further into the secrets and life of this amazing vertebrate.

Scientific classification

• Kingdom: Animalia (animals)
• Type: Chordata (chordates)
• Class: Chondrichthyes (cartilaginous fish)
• Order: Squaliformes (katraniformes)
• Family: Somniosidae (somnios sharks)
• Genus: Somniosus (polar sharks)
• Species: Somniosus microcephalus (Greenland shark)

Additional names: gray shark, scalugsuaq, sleeping shark, small-headed sleeper shark, and Atlantic sleeper shark.

In 1801, scientists first wrote about the view. The Greek terms for "head" and "small" are combined to form the species name "Squalus Microcephalus".

Geographical distribution

The Greenland shark is found in the Arctic, White, and Atlantic oceans in their northern regions. It was said to encounter her in the east toward France and Portugal, in the west toward the Bay of St. Lavrenty, and in the south toward North Carolina and the Cape Code. Polar sharks have even been observed on multiple occasions in Antarctic waters and the southern Atlantic Ocean, close to Argentina.

• Biogeographic regions: North Atlantic Ocean (native range)

Habitat

Because of its body’s adaptation to deep water living, the Greenland shark makes use of this feature. Although they typically swim in water that is a little bit deeper, at a depth of about 1200 meters, some members of this species have been discovered at a depth of 2200 meters. They find that a temperature of 0 to 12 °C is comfortable for them.

The shark migrates to the coast in the north in search of warmer waters. In winter, it is typically found close to the water’s surface, and in summer, it descends to a depth of 180 to 550 meters. The sleeper shark inhabits the southern waters near continental shelves and slopes, typically at a depth of 1000–1200 meters.

Image courtesy of NewsNeed News

At 2200 meters below the surface, an unmanned submarine in 1988 discovered a male Greenland shark measuring 6 meters in length. The ship, SS Central America, went down in 1857 off the coast of Savannah, Georgia. This is 440 km further south than the extreme location of the species’ discovery in North Carolina, and it is 1000 meters deeper than the maximum previously recorded diving depth of a Greenland shark.

The first Greenland shark was captured in the Gulf of Mexico by Florida researchers in August of 2013. The shark was swimming in water that was 4.1 °C at a depth of 1749 meters.

• Habitat regions: temperate, polar
• Aquatic biomes: pelagic, coastal
• Diving depth: up to 2200 meters

Distinguishing features

Anatomical features

The large, massive cylindrical body, short, rounded snout, thin lips, and tiny eyes of the Greenland shark are its distinguishing features. Its dorsal and pectoral fins are minuscule. Both the caudal peduncle’s lateral keels and the dorsal fins lack spines. The gill slits are low on the sides of the head and appear disproportionately small for the size of the animal.

Picture credit: Thinkstock/Dorling Kindersley RF

There are between 48 and 52 upper teeth, which are very thin, pointed, and lack serrations. They function similarly to an anchor that ensnared its prey. The lower teeth are square and broad, with 50–52 pieces total, and short, smooth protrusions pointing outward. Portioning food is the primary duty of the lower teeth.

Coloring

A shark may be gray, brown, or black in color. Despite the skin’s generally uniform tone, the sides and back frequently have white or dark lines.

Size

The Pacific sleeper shark, a cousin of the Greenland shark, challenges it to be the biggest shark in the Somniosidae family. It’s regarded as one of the biggest sharks alive, in fact. It is 400 kg heavier and reaches a length of 2.4–4.8 meters, making it slightly smaller than the great white shark. The largest specimens ever measured were over a ton in weight and measured 6.4 meters in length. Their growth is slowed by cold weather. The largest specimens have the potential to grow up to 7.3 meters in length and gain 1.5 tons of weight.

• Sexual dimorphism: female is larger than male
• Average body length: 244 to 427 cm
• Average body weight: 350 to 400 kg

The Greenland shark is the longest-living vertebrate, with some individuals estimated to be over 400 years old. Its unique habitat in the frigid Arctic waters adds to its fascination. This amazing longevity throws light on the mysteries of deep-sea life and the adaptations that enable it to flourish in such harsh conditions. It also raises questions about the factors that contribute to its longevity. We can learn more about marine biology and the tenacity of nature by investigating the life of the Greenland shark.

Eating habits

The Greenland shark is the top predator in polar waters, meaning it can hunt nearly any marine creature. Smaller sharks, rays, eels, cod, herring, salmon, flounder, capelin, grouper, and gobies are typically among its food sources. Despite their reputation as extremely slow animals, greenland sharks frequently capture marine mammals like seals and porpoises.

It is also known that carrion serves as a food source for Atlantic sleeper sharks, and they are drawn to meat with an unpleasant odor. In their stomachs, remains of moose, horses, polar bears, and reindeer have been discovered. They frequently congregate in big groups around fishing boats because the overpowering smell of fish emanating from the sides draws them in.

Lifestyle

The Greenland shark has a clumsy, slow gait. It can accelerate to a maximum of 2.7 km/h, but it can only reach a maximum speed of about 1 km/h. Because of this, the Atlantic sleeper shark is among the slowest species of sharks. It can travel at half a seal’s maximum speed.

So how do sharks from Greenland hunt bigger prey? According to scientists, they target their prey when it is sleeping.

See Morten Stroksnes’ photo.

Reproduction

The species of Greenland shark is ovoviviparous. Internal fertilization takes place. Summer is when the mating season peaks. A maximum of 500 soft-shelled eggs are carried by the female, from which approximately ten full-term embryos eventually hatch. Goose eggs can be found in some eggs.

• Mating system: polygamy
• Reproduction method: ovoviviparity
• Number of offspring: a dozen cubs
• Age of reproductive maturity: around 150 years

Life expectancy

It was once thought that the bowhead whale was the world’s longest-living vertebrate. Its longevity—it can live for over 200 years—is undeniable. On the other hand, evidence suggests that the Greenland shark has a 200-year lifespan.

Biologists began to wonder about the longevity of deep-sea animals as early as the 1930s. They came to the conclusion that the annual growth of the local ocean inhabitants was only 1 cm based on observations of 400 tagged sharks. It was thought that Greenland sharks had to have lived a very long time to grow to their size, given that they can reach a length of six meters.

Nevertheless, estimating the lifespan of Atlantic sleeper sharks has never been feasible. Fortunately, we are getting closer to learning how long these animals lived thanks to radiocarbon dating. By using this technique, it was determined in 2016 that the average lifespan of Greenland sharks is 272 years, with a maximum lifespan of 512 years!

The characteristic calcification of the pectoral fins, which serve a similar purpose to tree trunk growth rings, has also been used to estimate the lifespan of Greenland sharks. Nevertheless, since our main characters lack these hard bone structures, this method is not appropriate for them.

However, the most appropriate method of determining lifespan is not very sensitive and raises ethical concerns. Because the specimen’s eye lenses, which contain some information, must be removed in order to determine the specimen’s age. You can access the part of the shark that "remembers" its early years by removing the lens layer from the eye. This allows for the determination of the animal’s age.

Natural predators

The adult Greenland shark’s natural predators are unknown, probably because of its massive size. However, Ommatokoita elongata copepods actively parasitize it. When they adhere to the shark’s eyes, corneal lesions are created, which can result in blurry vision or even partial blindness. Since the marine animal does not depend on keen vision, this does not significantly affect it.

The females of these parasites, which are typically 3 cm long, are affixed to the shark’s eyes. It’s interesting to note that parasite-free sharks are very uncommon.

Copepods glow in the dark, so when Greenland sharks’ eyes glow green in the depths of the ocean, they appear almost demonic. The upside is that the shark can easily eat small fish and other marine life drawn to the glow.

Interaction with humans

Importance to humans

Shark meat is poisonous when consumed raw, but it can be eaten dried. In the north, dried meat is frequently fed to sled dogs and occasionally to people. Shark meat is processed to bring the toxin content down to a manageable level for a popular Icelandic dish called hákarl. The word "hákarl" means "healed shark" in Icelandic.

High levels of urea and trimethylamine oxide, which produce an intoxicating alcohol effect, are present in Greenland shark flesh. This explains why Greenlanders refer to each other as "shark drunks" so frequently.

The lower teeth of the shark are also used as knives by the Eskimos, mostly for hair cutting, and dried shark skin is used to make shoes.

Danger to humans

There has only ever been one known attack on a human by a Greenland shark, according to the International Shark Attack File (ISAF). A human foot was reportedly found inside the stomach of a Greenland shark that was captured in Pond Inlet, Canada, in 1859. But this was only a report, and it was never looked into or verified by science. The fact that there aren’t many attacks on record could mean that swimming in the shark’s habitat is too cold, which would significantly lessen the chance of a human being attacked.

Fact	Detail
Species	Greenland shark
Longevity	Can live over 400 years
Habitat	Cold waters of the North Atlantic
Growth Rate	Very slow, about 1 cm per year
Research Method	Carbon dating of eye lenses
Diet	Mostly fish and seals
Conservation Status	Not endangered, but vulnerable

The Greenland shark is an amazing animal. It is the longest-living vertebrate on the planet, with a lifespan that can exceed 400 years. This remarkable longevity provides an intriguing window into the mysteries of marine life and the centuries-long environmental adaptations made by certain species.

Even more fascinating is how little we actually understand about these sharks. They are elusive and challenging to research because they live in the chilly, deep waters of the North Atlantic. Because they experience such dramatic changes in their environment, sharks can offer important insights into the health of the ocean and the effects of climate change.

Gaining knowledge about Greenland sharks enables us to recognize the variety of marine life. It serves as a reminder that although many animals have brief lives, others can live for hundreds of years and adapt in ways that are still being discovered to their environment. The balance of marine ecosystems depends on protecting these extinct species and their habitats.

Therefore, let’s celebrate the Greenland shark and the larger oceanic world it represents as we learn more about this amazing animal. Every animal on Earth has a story to tell, and the Greenland shark is a living example of how resilient and adaptable nature is.

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