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Immortal Animals – 10 Animals Who Defy Death

Immortal Animals

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From times immemorial, we humans have thought and tried  many things in order to attain immortality. This endeavor includes the search for the so-called “Fountain of Youth” and even freezing cadavers in the hope of preserving and bringing them to life in the future.

Do you know, there are already many existing plant and animal species that are seemingly deathless, if not, can live for a very long time compared to the lifespan of humans!

Immortal Animals

Below are some of these amazing biologically immortal animals that actually live in this world.

1. Bdelloids (Lifespan One hundred million years – Immortal)

Immortal Animals

Bdelloidea is a class of rotifers found in freshwater habitats all over the world. There are over 450 described species of bdelloid rotifers (or ‘bdelloids’), distinguished from each other mainly on the basis of morphology.

The main characteristics that distinguish bdelloids from related groups of rotifers are exclusively parthenogenetic reproduction and the ability to survive in dry, harsh environments by entering a state of desiccation-induced dormancy (anhydrobiosis) at any life stage.

They are often referred to as “ancient asexuals” due to their unique asexual history that spans back to over 25 million years ago through fossil evidence. Bdelloid rotifers are microscopic organisms, typically between 150 and 700 µm in length. Most are slightly too small to be seen with the naked eye, but appear as tiny white dots through even a weak hand lens, especially in bright light. In June 2021, biologists reported the restoration of bdelloid rotifers after being frozen for 24,000 years in the Siberian permafrost.

Bdelloids can be considered “immortal” in a sense that they can tolerate extreme conditions like high heat, low temperature, and extreme pressure. Furthermore, they can also enter a state of “hibernation” and come back when they wish to do so.
Bdelloids dwell in the most ephemeral of freshwater habitats. Not just in small puddles, but in the transient layer of moisture sometimes found on moss or lichens – even on mushrooms. Desiccation is a routine occurrence which they handle with their own particular style of anhydrobiosis. Uniquely, they can withstand desiccation at any stage in their life cycle. Add water, and they re­hydrate and resume normal life activity and reproduction in a few hours. In the lab, they’ve been shown to revive after 9 years of “life without water.”

2. Hydra(Lifespan Immortal)

Immortal Animals

Hydra is a genus of small, freshwater organisms of the phylum Cnidaria and class Hydrozoa. They are native to the temperate and tropical regions. Hydra has a tubular, radially symmetric body up to 10 mm (0.39 in) long when extended, secured by a simple adhesive foot known as the basal disc. Gland cells in the basal disc secrete a sticky fluid that accounts for its adhesive properties.

At the free end of the body is a mouth opening surrounded by one to twelve thin, mobile tentacles. Each tentacle, or cnida (plural: cnidae), is clothed with highly specialized stinging cells called cnidocytes. Cnidocytes contain specialized structures called nematocysts, which look like miniature light bulbs with a coiled thread inside. At the narrow outer edge of the cnidocyte is a short trigger hair called a cnidocil. Upon contact with prey, the contents of the nematocyst are explosively discharged, firing a dart-like thread containing neurotoxins into whatever triggered the release. This can paralyze the prey, especially if many hundreds of nematocysts are fired.

Biologists are especially interested in Hydra because of their regenerative ability; they do not appear to die of old age, or to age at all. According to studies, the hydra is one of the few animals that does not show any signs of deterioration with age. Being able to continuously divide and regenerate new body cells, hydras can basically keep themselves young for long periods of time (even until forever).

3. Jellyfish(Lifespan Immortal unless disease or predation)

Immortal Animals

Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile.

The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, which produces planula larvae that disperse widely and enter a sedentary polyp phase before reaching sexual maturity.

Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the “true jellyfish”) are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal group.

4. Tree Weta/ Zombie Bugs(Immortal unless predation)

Immortal Animals
Tree Weta

Tree weta are weta in the genus Hemideina of the family Anostostomatidae. The genus is endemic to New Zealand. Because many tree weta species are common and widespread they have been used extensively in studies of ecology and evolution. Tree weta are commonly encountered in forests and suburban gardens throughout most of New Zealand.

 They are up to 40 mm long and most commonly live in holes in trees formed by beetle and moth larvae or where rot has set in after a twig has broken off. The hole, called a gallery, is maintained by the wētā and any growth of the bark surrounding the opening is chewed away. Tree weta are nocturnal and arboreal, hiding in hollow tree branches during the day and feeding at night. Their diet consists of leaves, flowers, fruit and small insects. Males have larger heads and stronger jaws than females, though both sexes will stridulate and bite when threatened.

These bugs are very resilient to freezing as they have special proteins in their blood that prevents this from happening. While their hearts and brains are not that resistant to freezing and can die when completely frozen, they can be ‘revived’ to life when thawed out.

5. Glass Sponges(Lifespan 15,000 years)

Immortal Animals
Glass Sponges

Glass sponges in the class Hexactinellida are animals commonly found in the deep ocean. Their tissues contain glass-like structural particles, called spicules, that are made of silica (hence their name). Some species of glass sponges produce extremely large spicules that fuse together in beautiful patterns to form a “glass house”—a complex skeleton that often remains intact even after the sponge itself dies.

The skeleton of the glass sponge, together with various chemicals, provides defense against many predators. Nonetheless, some starfish are known to feed on these rare creatures of the deep.

Most glass sponges live attached to hard surfaces and consume small bacteria and plankton that they filter from the surrounding water. Their intricate skeletons provide many other animals with a home.

Although they’re not necessarily deathless (due to some inevitable instances like being eaten by predators), some species of glass sponges can survive up to more than 15,000 years! This is because some species can control the growth of their spicules (mineralized structures) at a very slow rate, hence slowing down their aging process.

6. Aldabra Giant Tortoise (Lifespan 200+ years)

Immortal Animals
Aldabra Giant Tortoise

The Aldabra Giant Tortoise is a giant species of Tortoise native to the Aldabra Islands in the Indian ocean. The Aldabra giant tortoise is one of the largest species of Tortoise on the planet and is also one of the world’s longest living animals, with one Aldabra Giant Tortoise individual reaching the grand old age of 255 years old. One such tortoise was Adwaita at the Alipore Zoological Gardens in Kolkata India.

These tortoises take a very long time to grow as they do not reach sexual maturity until over 30 years old. However, scientists have revealed that some may have persisted twice that age.

Tortoises like to take it slow — so slow that it takes them forever to die. Tortoises have a sluggish metabolic rate. Tortoises’ slow metabolism is thought to contribute to their longevity. The ability of the animal to have a slower metabolic rate enables it to consume less energy. The age at which tortoises first procreate varies from a few years to as many as 50, with smaller species often reaching sexual maturity earlier. This shows how tortoises are built to take their time in life. As if to prove that slow and steady wins the race when it comes to longevity!

When researchers got around to actually taking a look inside a century-old turtle, something they’d amazingly never thought of doing before, they were astounded to find that its organs were virtually “indistinguishable from those of its teenage counterpart.” Biologically, the turtle hadn’t aged a day since hitting sexual maturity, a phenomenon scientists have dubbed “The Don Draper Effect.”

The research has led scientists to believe that turtles are biologically immortal! Of course they die, but  never seem to die of old age. It’s always a disease, or a falling boulder, or any other such reason.

7. Bowhead Whales (Lifespan 200+ years)

Immortal Animals
Bowhead Whale

Bowhead whales are huge freaking whales endowed with the largest mouth of any animal — they basically just swim around giving the ocean a huge blow job all the time. Aside from their humongous size, another astonishing fact about bowhead whales is that they can live up to more than a hundred years.

Seriously, if there’s a mammal that lives longer than them, no one’s been able to prove it. One was determined to be 211 years old. Scientists used to think bowhead whales lived 60 or 70 years, but in 2007, some Native Alaskan hunters killed one and found a surprising artifact from another era inside.

The secret to this? They can repair damaged DNA, hence are prevented from developing cancer. Scientists also suggested that these whales can survive the absence of oxygen even for a long time.

Based on analysis of these Arctic cetaceans’ genome back in 2014–2015, scientists have revealed that they possess anti-ageing DNA-repair systems, far more potent than any other living creature – probably as a means to compensate for their relatively slow rate of growth and late age of reproductive maturity (around 15–25 years of age) –, which gives them the ability of keeping disease-causing genetic mutations at bay, leading a life free of various maladies like cancer, and thus outliving almost all other animals.

Other scientists speculate that it may have to do with the bowhead whale’s extremely cold environment, which made it evolve with great body mass (a maximum length of 18–20 meters long, and a maximum weight of 200 tons), an effective system for fat storage and an efficient mechanism to keep warm – as such, life in the freezing Arctic waters may have contributed to the whale’s pattern of slow growth and expanded longevity, providing the species with a better chance of reproducing.

8. Red Sea Urchin(Lifespan 200+ years)

Immortal Animals
Red sea urchin

The red sea urchin (Mesocentrotus franciscanus) is a sea urchin found in the northeastern Pacific Ocean from Alaska to Baja California. It lives in shallow waters from the low-tide line to greater than 280 m (920 ft) deep, and is typically found on rocky shores sheltered from extreme wave action in areas where kelp is available.

A sea urchin’s spherical body is completely covered by sharp spines. These spines grow on a hard shell called the “test”, which encloses the animal. It can vary in color from red to dark burgundy. Rarely, albino specimens are found. It has a mouth located on its underside, which is surrounded by five teeth. During larval development, the body of a sea urchin transitions from bilateral to radial symmetry.

Living on seaweeds in shallow waters, Mesocentrotus franciscanus or the red sea urchin is considered to be “practically immortal“. Although amazing as it may sound, scientists say these urchins can never stop growing but don’t get old. While they can live up to more than a hundred years old, some may reach up to 200 years, given that the environmental conditions are good.

9. Lobsters(Lifespan 100+ years unless predation)

Immortal Animals

Lobsters are a family of large marine crustaceans. Lobsters have long bodies with muscular tails, and live in crevices or burrows on the seafloor. Three of their five pairs of legs have claws, including the first pair, which are usually much larger than the others. 

Scientists suggested that through time, some lobsters can persist and even increase their fertility because of a certain enzyme called telomerase. This enzyme repairs the lost sections of the DNA; hence, “aged” cells are again reverted to being young. Though such a process renders them to stay “deathless“, the exact lifespan of a lobster is difficult to determine because of the regular molting of the exoskeleton.

They do not die of aging. Instead they have an enzyme called telomerase which replaces their cells and will do so as long as they live. Their longevity is thanks to telomerase which is able to endlessly repair their telomere that is lost when their cells divide. 

Lobsters can defy the laws of aging however, we can’t quite place them under the category of being biological immortality. The older a lobster gets the bigger it grows. Eventually they will outgrow their shell. The problem arises when they’re at their oldest stage of life. The lobster will continue to grow and grow but their shell simply can’t keep up. Once they get to a certain size it takes too much energy for them to be able to survive. After a while they will die of either exhaustion, disease, predication or lastly a shell collapse.

10. Lungfish(Lifespan 100+ years)

Immortal Animals

Lungfish are freshwater animals, also known as rhipidistian, they are vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton. Lungfish represent the closest living relatives of the tetrapods.

Lungfishes are one of the oldest species of fish on the planet and unlike other fishes, they can breathe out of water and survive for long periods of time. In addition to that, they can slow down their metabolic rate and live even without nutrients for years!

Unlike most aquatic creatures, they have learned to endure the occasional prolonged dry spell, with one branch of the family even doing so yearly. They burrow themselves deep down into the ground and secrete a mucous substance around them which preserves the moisture in their bodies. Their metabolic rate then drops into a state of aestivation, allowing them to go without nutrients for very long periods of time.

A science lab in East Africa witnessed this phenomena firsthand when a lungfish, while being transported in an air-tight metal cylinder full of mud (a method of travel a lungfish could easily survive for a brief time), became lost during the trip. When they finally recovered it after six months of being shipped from lab to lab, the mud in the cylinder had long since hardened and the air had been depleted, basically burying the poor thing alive. They buried it alive without air or moisture for six months and couldn’t kill it.

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Image Credit: Seabed vector created by macrovector – www.freepik.com

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