Since time mmemorial, humans have coveted and sought the fabled ‘fountain of youth.’ To live forever is a notion reserved for science fiction and vampire dramas, but what if it were possible? For a select few animals, immortality is a reality.*Note: While there are various more animals that effectively resist the effects of aging, this list is only composed of animals that are thought to be truly immortal, not just long lived.
Hydra are tiny creatures that can be found in most freshwater lakes, ponds, and streams. As they are only a few millimeters long they require a microscope to be observed. While these minuscule organisms might slip right by the naked eye, biologists and other scientists are transfixed on studying them. The reason is that hydra don’t age, not even slightly; they are truly immortal.
The source of hydra immortality lies in their ability to maintain telomere length. Each time a cell divides, telomeres, additional strands of DNA at the end of chromosomes, shorten and get chipped away. This is what causes aging and the corrupted replication of cells in all life forms, including humans. This aging process, or senescence as it is called in the scientific community, leads to age related illnesses such as cancer, and eventually death. In hydra, telmores never get shorter. Although it is unknown precisely how hydra maintain their telomere length so impeccably, recent studies have revealed that a gene called FoxO, which has a direct influence on stem cells, is likely the answer. When FoxO activity is reduced in Hydra their powers wane and they suddenly show signs of aging.
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This is particularly exciting because FoxO is also responsible for stem cell activity in humans. Greater FoxO activity is routinely found in people with abnormally long lifespans, like centenarians. It may be possible to increase FoxO activity from an early age, maintain levels of stem cells in the body, and thus increase human lifespan by 1000’s of years; maybe even forever.
Jellyfish come in all shapes and sizes, but one particular jellyfish is especially baffling; the immortal jellyfish. Technically called Turritopsis nutricula, the immortal jellyfish has the ability to, at any strage of its life, completely reverse its aging process.
Jellyfish begin as small polyps on the ocean floor. These polyps branch off and eventually grow into medusas, or sexually mature jellyfish, with tentacles and the traditional jellyfish-look we all know and adore. The immortal jellyfish holds the title of being the only animal with the ability to revert back into a sexually immature state after being sexually mature. The medusa form of the immortal jellyfish reverses the aging process through a method known as cell transdifferentiation. This process transforms cells into a different cellular state, including earlier states. As the cells transform, the medusa retracts its tentacles and head into itself, turns back into a polyp, embeds itself back into the ocean floor, and starts life all over again.
For some human perspective, imagine all the cells in your body suddenly transforming into stem cells as your body shrinks and reverts back into an infantile state. From deathbed to birthing room in the blink of an eye.
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Interestingly, immortal jellyfish have a choice to drink from the fountain of youth or not. While some jellyfish reset life early on, others choose to brave the struggle of old age and eventually die without the opportunity for a second chance. Who can really blame them though? Without Wondergressive or pirated entertainment, what’s the point of living?
Lobsters, the hallmark of a luxury dinner and recently discovered abundant power source, are also immortal. While scientists have never found a 10,000 year old lobster lurking on the ocean floor, at the cellular level, they age at a negligible rate. As long as lobsters are not hunted, fatally injured, or killed by disease, they could live indefinitely. It gets even stranger, as lobsters become more fertile as they age:
They don’t slow down or become weaker or more susceptible to disease. They don’t get infertile — older lobsters are actually more fertile than younger ones.
This is unprecedented! Ladies, can you imagine getting menopause out of the way when you are 10 and being at the height of your sexual activity when you are 90? Welcome to the life of a lobster.
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Scientists believe that like hydra, lobsters are able to beat the aging process through the maintenance of its telomeres, as lobsters produce a large amount of telomerase, the enzyme responsible for ensuring the health and longevity of telomeres.
As lobsters age, they continue to grow larger and larger, making it easy to guess the age of a lobster based on its size. The largest recorded lobster ever caught was in Nova Scotia, Canada, weighed 44.4 lbs and was believed to be 50 years old.
Planarian flatworms are non-parasitic worms that are found all over the world; in saltwater, freshwater, soil, and more. They are very common, and come in the asexual and sexual variety, take your pick. No matter which type you choose, you’ll still be choosing another immortal animal.
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Through plentiful adult stem cells and a high production of telomerase, planarian flatworms have an infinite regenerative ability. This incredible regeneration applies not only to the general maintenance of its body, but also to an unprecedented level of repair in the event of physical damage.
Planaria can be cut into pieces, and each piece can regenerate into a complete organism. Cells at the location of the wound site proliferate to form a blastema that will differentiate into new tissues and regenerate the missing parts of the piece of the cut planaria.
1/279th of a piece of planarian flatworm can be cut from its body and will grow into a new, completely independent flatworm within a few weeks. You can slice and dice this animal into hundreds of pieces and you’ll just be left with more worms!
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Even more interestingly,
if the head of a planaria is cut in half down its centre, and each side retained on the organism, its possible for the planaria to regenerate two heads and continue to live.
Imagine if every time you cut yourself shaving a mini-you started writhing and growing in the sink. In this way, the planarian flatworm can continuously regrow itself and remain immortal through countless copies.
Tardigrades are also called waterbears, or moss piglets, because under a microscope, that’s exactly what they look like. They are one of the most well known extremophiles; animals that can survive under conditions fatal to most other forms of life. They are usually around 1 millimeter in length and can be found absolutely everywhere on the planet, from common streams, to moss in your backyard, to the top of the Himalayas, and even in newly discovered ecosystems. They prefer places with lots of moisture, but as you’ll soon see, it really doesn’t matter to them where they live.
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Although Tardigrades aren’t immortal in the same sense as the animals listed above, they have the incredible ability to survive in nearly every environment known to man, including the vacuum of space, by entering a state of suspended animation called cryptobiosis where their metabolism reaches near zero. They can stay in this state for more than ten years, return to normal, and go right back into the suspended state for another 10 years of rest and relaxation. They are their own cryogenic tanks.
Tardigrades have been observed surviving extreme conditions such as:
Pressure of more than 6,000 atmospheres (six times the pressure of water in the Mariana trench)
Tardigrades are naturally indestructible, and if they desire to be, are also immortal.
All of these animals and their remarkable anti-aging abilities are creating new opportunities for scientists to actually discover and synthesize the ‘fountain of youth.’ In fact, many prominent scientists believe that the solution(s) to old age and even death is right around the chronological corner. According to Aubrey de Grey, a British researcher on aging and life extension, the first human being to live to 1000 years old has already been born. It might even be you…
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