The ocean holds many mysteries, including the remarkable longevity of some inhabitants. Life in the deep sea often unfolds at a pace far different from that on land, allowing certain organisms to achieve ages that defy typical understanding. Exploring these ancient ocean dwellers offers a glimpse into the diverse strategies life employs to persist through deep time.
The Greenland Shark
The Greenland shark, Somniosus microcephalus, is the longest-living known vertebrate. Its lifespan is estimated to range from at least 272 years and potentially exceed 500 years, with one individual estimated at 392 ± 120 years old. Scientists determine their age by radiocarbon dating specific proteins in their eye lenses that form before birth and remain stable throughout life.
They inhabit the frigid, deep waters of the North Atlantic and Arctic Oceans, often found at depths up to 2,647 meters. Their exceptionally slow growth rate, approximately 0.5 to 1 centimeter per year, contributes to their extended lifespan. They also reach sexual maturity at an advanced age, around 150 years old. Recent research suggests their stable metabolism, which resists degradation, also plays a role in their remarkable longevity.
Other Ancient Ocean Inhabitants
Beyond the Greenland shark, many other marine organisms exhibit extraordinary lifespans. The ocean quahog, Arctica islandica, is the longest-lived individual non-colonial animal discovered. One specimen, “Ming,” found off the coast of Iceland, was 507 years old. Its age was calculated by counting annual growth rings on its shell, similar to tree rings. The cold waters of its habitat contribute to its slow metabolism, supporting its extended life.
Deep-sea sponges, such as Monorhaphis chuni, represent an ancient lineage with some individual specimens or colonies living for thousands of years. Monorhaphis chuni, a glass sponge found at depths up to 5,000 meters, is estimated to live for 11,000 to 15,000 years. Their age is determined by analyzing layered rings within their silica-based skeletal structures, called spicules. This extreme longevity is linked to their very low metabolic rates.
Tube worms, including species like Lamellibrachia luymesi and Escarpia laminata, are known for their long lives in deep-sea environments. Lamellibrachia luymesi can live for 170 to 250 years, with some individuals potentially exceeding that range. Another species, Escarpia laminata, has been found to live between 100 and 200 years, with some specimens living over 300 years. These creatures thrive in chemosynthetic environments, like cold seeps, where they grow at an exceptionally slow pace.
A different form of longevity is seen in the “immortal jellyfish,” Turritopsis dohrnii. This tiny creature possesses biological immortality, reverting to its juvenile polyp stage when faced with stress or injury. This process, known as transdifferentiation, allows it to theoretically reset its life cycle indefinitely. However, in natural environments, these jellyfish can still succumb to predation or disease, preventing true endless life.
Secrets of Marine Longevity
The remarkable longevity observed in various marine organisms is linked to environmental conditions and biological adaptations. Cold temperatures are a significant factor, as they slow down metabolic rates and cellular processes. This reduces cellular damage accumulation, extending lifespan.
The deep-sea environment provides stable conditions that contribute to extended lifespans. This habitat features low predation pressure and consistent, cold temperatures, reducing energy expenditure. Limited food availability also favors organisms with slower growth and reduced metabolic needs, conserving energy over long periods.
A general pattern among long-lived marine species is their slow growth and maturation rates. Organisms that grow slowly and reproduce later in life often invest more resources into cellular maintenance and repair, leading to a longer overall lifespan. This strategy is an adaptation to environments where survival to older ages is more probable. Beyond environmental factors, some species possess unique biological adaptations, such as efficient DNA repair mechanisms or specialized proteins that contribute to their resilience against aging.
When discussing “oldest” sea creatures, it is important to clarify what “oldest” signifies. It can refer to the oldest individual animal, like the Ming clam, which lived for centuries. It can also denote the oldest species, such as the Greenland shark, which as a species holds the record for vertebrate longevity. Finally, it can refer to an ancient lineage, like deep-sea sponges, which include individuals with multi-millennial lifespans. These distinctions highlight the diverse ways marine life has evolved to achieve extraordinary longevity.