The Greenland shark is a behemoth, reaching up to 6.4 meters (21 feet) long and weighing over 1,000 kilograms (2,200 pounds). With a thick, gelatinous body and a sluggish swimming speed of roughly 0.76 meters per second (1.7 mph), it moves with a ghostly elegance, earning it the nickname “zombie shark.” Its more-than-likely parasitic covered eyes and poor vision suggests it lacks great sight, but it is capable of maneuvering through pitch-black waters due to its excellent sense of smell. It unusually resides alone, hardly engaging with other sharks. The combination of living an almost solitary lifestyle and being able to ambush prey, seals for instance, like a seal makes it a one of a kind predator in the Arctic Ecosystem.
What enables a creature to live for centuries? The longevity of the Greenland shark is an enduring scientific riddle, but modern techniques are helping to solve it. Unlike other sharks, it has no growth rings in its vertebrae, so scientists estimate age by radiocarbon dating eye lens proteins. The sharks were estimated to be 272 years old with some possibly reaching 392 years or more, making them the longest-living vertebrates known (BBC News: Greenland Shark). Their remarkable lifespan is also due to their slow growth, about one centimeter a year, and late maturity, which is around 150 years. Newer studies indicate that their metabolism stays consistent throughout their life span, a quality that may reveal other ways to study aging in different species.
Greenland sharks thrive in the frigid depths of the North Atlantic and Arctic Oceans, where temperatures range between -1.1 °C to 7.4 °C (30 °F to 45.3 °F) and are found from 0 to 1,500 meters deep, with diving records reaching 2,200 meters. These species of sharks undergo seasonal migrations to shallower areas during winter and deeper, southern regions during summer, displaying adaptability to extreme water conditions. Unlike other sharks, these are the only species that can withstand the Arctic waters throughout the year. The astonishing sighting of a Greenland shark or its hybrid off Belize’s Glover’s Reef back in 2022 hints towards deeper, possibly tropical waters, expanding the understanding of their habitat.
Greenland sharks are apex predators, feeding on a variety of marine life which includes seals, fish, squid, and seabirds. They scavenge for carrion and have been found with the remains of moose, reindeer, and even polar bears in their stomach, suggesting those were likely consumed while dead. Being slow swimmers does not impact their hunting abilities. Their powerful suction feeding allows them to ambush their prey at close range. As vital scavengers in their ecosystem, they possess a keen sense of smell which allows them to detect decomposing meat from great distances. Their role as both opportunistic feeders and apex predator demonstrates the vital role they play on the balance of Arctic and North Atlantic marine ecosystems.
Like its lifestyle, the reproductive cycle of the Greenland shark is equally slow. It has an incredibly lengthy gestation period, econsisting of 8 to 18 years, making it one of the longest in the animal kingdom. Females attain sexual maturity at around 150 years of age and give birth to small litters of 2 to 10 pups, who are each approximately 38 to 42 cm long. Their sluggish reproduction rate coupled with a prolonged life span makes them increasingly susceptible to declining populations. The IUCN Red List classifies these sharks are “Vulnerable”, listing potential overfishing for their squalene-rich liver oil and bycatch in fisheries as some of the issues they face. Protecting these ancient shark species is crucial for unlocking truths surrounding adaptation and longevity as well as protecting our marine ecosytem.
The trace of history - is in motion deep down in the oceans, where the Greenland shark makes its solo offer. It inspires awe and challenges everything we know about biology with its solitary centuries long life and ability to thrive in harsh conditions. Thr Greyland shark offers researchers a glimpse into longevity along with marine ecosystems, and serves as a great reminder of the unexplored beauty hidden in oceans for students and ocean lovers. There is no doubt the shark offers us the chance to understand how we can preserve our seas while ensuring the health of the species that have silently observed life. The shark in countless ways has, does and will continue to inspire us to safeguard the balance of life our oceans have to offer.
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