The animal kingdom contains creatures with lifespans far exceeding human understanding, prompting curiosity about extreme longevity. These organisms offer a glimpse into biological processes that defy typical aging, showcasing remarkable adaptations. Studying them can unravel mysteries of life and aging.
The Record Holder
The Greenland shark, an elusive predator inhabiting the frigid depths of the North Atlantic and Arctic Oceans, holds the record for the longest-living vertebrate. These sharks can reach an estimated maximum lifespan of 272 to 500 years, with one individual believed to be around 392 years old.
These sharks exhibit a very slow metabolism and growth rate. They grow less than half a centimeter per year and move sluggishly. Greenland sharks do not even reach sexual maturity until they are approximately 150 years old. Their extreme longevity was determined through radiocarbon dating of proteins in their eye lenses, which form before birth and do not degrade.
Other Remarkable Longevities
While the Greenland shark holds the vertebrate record, other animals also display astonishing longevity. The ocean quahog, a type of clam found in the North Atlantic, is considered the longest-living animal on Earth, with one specimen nicknamed “Ming” estimated to be 507 years old. These clams show annual growth rings on their shells, similar to tree rings, which scientists use to determine their age.
Bowhead whales, inhabitants of Arctic and sub-Arctic waters, are the longest-living mammals, with some individuals living over 200 years. Evidence for their age comes from stone harpoon tips found embedded in their blubber. Giant tortoises, such as the Aldabra and Galapagos giant tortoises, are also known for their long lives, often exceeding 150 years, with some reaching over 200 years.
Biological Keys to Longevity
Slow metabolism is a common characteristic in long-lived animals, as seen in the Greenland shark, which thrives in near-freezing waters. Cold environments slow down metabolic processes and biochemical activity. A recent study suggests the Greenland shark’s metabolism remains remarkably stable throughout its life, minimizing cellular damage.
Robust cellular maintenance and efficient DNA repair mechanisms are also common. For instance, bowhead whales have an extraordinary ability to repair damaged DNA with high efficiency and accuracy, helping them avoid cancer and other age-related diseases. Research into Greenland sharks has revealed multiple copies of genes related to the NF-κB signaling pathway, which supports the immune system and regulates inflammation, and genes involved in DNA repair. Maintaining cellular integrity and repairing damage over extended periods is a recurring theme in these exceptionally long-lived organisms.
Measuring Immense Lifespans
Determining the age of animals that live for centuries or millennia requires specialized techniques. For the Greenland shark, scientists utilize radiocarbon dating of proteins within the central lens of their eyes. These proteins form before birth and remain unchanged. The presence of radioactive carbon-14 from atmospheric nuclear bomb testing in the mid-20th century helps to date individuals born around that time.
For species with hard structures, such as the ocean quahog, age is determined by counting annual growth rings on their shells, similar to tree rings. In bowhead whales, age can be estimated by analyzing stone harpoon tips embedded in their blubber from past hunting. Another method involves examining the aspartic acid in their eye lenses, which undergoes a process called racemization that correlates with age. These diverse methods allow scientists to unlock the secrets of extreme longevity across the animal kingdom.