Key Takeaways

• Greenland sharks, also known scientifically as Somniosus microcephalus or more commonly as "gray, ground, gurry, or sleeper sharks," are the longest living vertebrates and the second largest carnivorous sharks on earth.
• These fish live for between 272 and 512 years each, compared to the average lifespan of 20 to 30 years for other shark species.
• Several theories exist for why Greenland sharks have such a long lifespan. For instance, scientists highlight that the Greenland shark has a "very slow metabolism," likely resulting from a combination of their size and habitat in icy-cold seawater.
• Consistent with their long lifespans, Greenland sharks aren't believed to reach sexual maturity until after a century of life (or at least 134 years), versus the decade or so that many other shark species require to mature.

Introduction

Description

• Greenland sharks, also known scientifically as Somniosus microcephalus or more commonly as "gray, ground, gurry, or sleeper sharks," are the longest living vertebrates and the second largest carnivorous sharks on earth.
• They belong to the family of sleeper sharks and are covered in "teeth-like scales, called dermal denticles," which help them move stealthily in water.
• From a distance, Greenland sharks may resemble a submarine, owing to their cylindrical shape, dark gray, brown, or black coloring, and large size (up to 23 feet long and 1.5 tons in weight).

 

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• These predators consume both live prey as well as scavenge dead animals, such as "other sharks, seals, drowned horses and polar bears." They also sometimes display cannibalistic behaviors. They have very few natural enemies, apart from sperm whales, and have never been known to attack humans.
• However, Greenland sharks are currently considered by the IUCN to be "vulnerable" to extinction due to human activities, such as overfishing, where they are often bycatch.

Lifespan

• The latest available estimate for the lifespan of a Greenland shark indicates that these fish live for between 272 and 512 years. Even at the lower end of this range, Greenland sharks qualify as the longest living vertebrate on the planet.
• In comparison, the average age of sharks in the wild is between 20 to 30 years. Additionally, other longest-living vertebrates only come close to the age of a Greenland shark, with bowhead whales living between 100 to 200+ years and rougheye rockfish having a lifespan of up to 205 years. Galapagos tortoise can live over 100 years in the wild.
• Only estimates for the lifespan of Greenland sharks are available, however, because more traditional methods for determining the age of shark species (e.g., growth bands on fin spines/vertebrae) can not be utilized for Greenland sharks. Instead, proteins in the sharks' eyes are carbon dated, which provides an age range rather than a "definitive age."
• Meanwhile, several theories exist for why Greenland sharks have such a long lifespan. First, scientists highlight that the Greenland shark has a "very slow metabolism," likely resulting from a combination of their size and habitat in icy-cold seawater.
• The fact that they move slowly (with a maximum speed of less than 2.9 kilometers per hour) and are able to live off of a single meal for up to a year serves as evidence of this "slow way of life" and high level of energy efficiency.
• Other scientists point to the freezing temperatures that surround Greenland sharks as the key to their long survival rates, suggesting that the cold could provide "anti-aging qualities." Notably, these fish can dive up to 2,200 meters below the water's surface and survive the Arctic Ocean year-round.
• Additionally, as described in the preceding section, Greenland sharks have very few–if any–natural predators in the wild, which contributes to longer survival timeframes.
• While trying to uncover the secret of the Greenland shark's longevity, scientists are also interested in unique genetics. They believe its heart may beat for so long because it has a "sophisticated system to repair damaged DNA." They also study the animal's immunity, wondering how it can fight off pathogens and cancer without bone marrow. Their research focuses on gene mutations in the major histocompatibility complex by comparing the DNA to the samples from other shark species.
• Researchers hope studying the Greenland shark can help with new drug development, particularly for preventing age-related changes to the heart.

Sexual Maturity

• Consistent with their long lifespans, Greenland sharks aren't believed to reach sexual maturity until after a century of life.
• The latest estimate published in the Journal of Science suggests that the animals must be at least 134 years old before they become fertile.
• Additionally, female Greenland sharks must measure at least 3.9 meters before they can reproduce, while male counterparts may be slightly smaller at 2.7 meters before they become sexually active.
• In contrast, other shark species living in the wild may take closer to a decade or so to reach sexual maturity.
• For example, bull sharks mate starting at the age of eight or 10, copper sharks become sexually mature between 13 and 20 years, and whale sharks become fertile between the ages of 30 and 50 (depending on gender).

Other Unique Qualities

• In addition to being differentiated by their relatively late fertility, Greenland sharks are believed to be among the shark species that have the most offspring per pregnancy (between 200 and 324 pups or more).
• They are also known for being partially blind, owing to the ocean parasites (known as Ommatokoita elongata) that frequently live in a typical Greenland shark's eyes.
• Meanwhile, although Greenland sharks are not known to attack humans, their meat is toxic to people due to its levels of trimethylamine oxide. However, their meat can be consumed when it is dried and is considered a delicacy in Iceland.

Research Strategy