The average life expectancy of a human being is 71.5 years according to the United Nations World Population Prospects – 2015 Revision. That is, 68 years and four months for males and 72 years and eight months for females. The World Factbook puts our average life expectancy at 69 years in 2016. The oldest living person was Jeanne Calment who lived until the grand old age of 122 years and 164 days. However, this is nothing compared to certain animals who live for centuries. Read on to find out more about these awesome, age-defying animals, some of whom have been around since the time of Shakespeare.

1. Turritopsis dohrnii

There exists a species of jellyfish which is biologically immortal. They can live forever unless killed, attacked, or damaged.

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Turritopsis dohrnii aka immortal jellyfish
Image credits: Bachware/wikimedia, Zina Deretsky, National Science Foundation/wikimedia

The Turritopsis dohrnii is also known as the “immortal jellyfish” and was discovered in the Mediterranean Sea in 1883. They are said to have originated in the Pacific but are now found in various other places in the world thanks to trans-Arctic migration. They have the unique ability to revert to an immature stage after they’ve reached sexual maturity making them biologically immortal. After they reach adulthood and have reproduced, instead of dying, they turn themselves into a cyst which looks like a blob. When this happens, their tentacles withdraw and bodies become smaller. This cyst turns into a polyp colony which is the first stage in its life, thereby skipping the stage of death. The immortal jellyfish accomplished this through “transdifferentiation,” which changes the differentiated state of cells and turns them into new kind of cell. They can undergo this cycle repeatedly.

Lab studies have revealed that all the specimens collected displayed this ability making them one of the most unique animals on this planet. Maria Pia Miglietta, a researcher at Pennsylvania State University, says that “..when starvation, physical damage, or other crises arise, instead of sure death, [Turritopsis] transforms all of its existing cells into a younger state.”

2. Sea sponges

Sea sponges are multicellular organisms with porous bodies. Certain species of sea sponges are said to have a lifespan of more than thousand years, and some even more than ten thousand years.

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Glass sponges aka Hexactinellid sponges
Image credit: NOAA Photo Library/flickr

That’s right, sponges are also animals, although most people mistakenly categorize them as plants. They are all immobile, aquatic animals and some have the longest lifespan of any known animal. Scientists at the Max Planck Institute for Chemistry studied the skeleton of the glass sponge found in the East China Sea and discovered that it was more than 11,000 years old. Another specimen of Antarctic sponge found in the Southern Sea was found to be approximately 1,500 years old. They grow at a very slow rate, possibly due to the very low temperatures.

A study published in 2016 by Daniel Wagner, Papahānaumokuākea research specialist, and his colleague, says that “While not much is known about the lifespan of sponges, some massive species found in shallow waters are estimated to live for more than 2,300 years.” Wagner said that sponges don’t have indicators of age like growth rings, but they can live for thousands of years. They had discovered a massive glass sponge near Hawaii which they estimate is around 1,000 years old.

There are a few tropical and deep-sea sponges that have a lifespan of 200 years, maybe even more. Additionally, by taking into account their growth rate, some calcified demosponges are up to 5,000 years old.

3. The Ocean quahog

The ocean quahog is essentially a mollusk or a clam whose average lifespan is 400 years. A particular specimen was said to be as old as 507 years old, according to its growth rings. However, many don’t live up to that old age since they are also used as a food source.

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Ocean Quahog aka Arctica islandica
Image credit: Hans Hillewaert/wikimedia

The ocean quahog, or Arctica islandica, is basically an edible clam and is found in the North Atlantic Ocean. You may also know it as the mahogany clam, black quahog, or black clam. Doris Abele, a German animal physiologist and marine biologist, has stated that the ocean quahog has such a long lifespan mainly because of its extremely slow metabolism. It consumes very less oxygen leading to a slow metabolism and hence the long life. She also attributes its long life to its genes. Its age can be determined by counting the rings on its shell, as well as employing the carbon-14 dating method.

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In 2006, a research group discovered a 507-year-old quahog in Iceland. Unfortunately, it died as a result of being frozen on board before they discovered its age. The clam, named Ming after the Ming Dynasty which was in power when it was born, is now in the Guinness Book of World Records as the “longest-lived, non-colonial metazoan whose age was accurately known.” The previous record was held unofficially by a 374-year-old clam found in 1868 near Iceland.

4. Greenland shark

There is a species of shark found in the frigid waters of northern Atlantic and Arctic oceans which can live for up to 400 years. Their average lifespan is between 272 and 512 years.

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Greenland shark (Somniosus microcephalus)
Image credit: NOAA Okeanos Explorer Program/wikimedia

Found in the North Atlantic and Arctic Oceans, these sharks are the longest-lived vertebrates found on earth. They only attain sexual maturity at around 150 years of age. Although not much is known about them, a study conducted by Julius Nielson and marine biologist John Steffensen at the University of Copenhagen managed to determine the ages of 28 dead, female sharks by using the radiocarbon dating technique on the lenses of their eyes. The oldest one was estimated to be 392 years old, give or take 120 years.

Clues to their longevity can be attributed to several factors like their slow growth rate of one-cm per year and slow metabolism. A geneticist at the University of Michigan, Shawn Xu, discovered that the frigid cold might activate anti-aging genes in animals. This could help in folding protein, doing away with molecules that damage DNA, and also prevent infections thereby extending its lifespan. This anti-aging gene could be present in Greenland sharks and could explain their incredibly long lifespan.

5. Lamellibrachia luymesi

The Lamellibrachia luymesi is a species of deep-sea tube worm, which can live for up to 250 years.

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Lamellibrachia luymesi aka Deep-sea Tube Worms
Image credit: Charles Fisher/wikimedia, Erik E. Cordes, Michael A. Arthur, Katriona Shea, Rolf S. Arvidson & Charles R. Fisher/wikimedia

These deep-sea tube worms live in the cold seeps in the Gulf of Mexico and are presently the longest-lived, non-colonial invertebrates. According to Charles Fisher, professor of Biology at Penn State, an average two-meter-long tubeworm is 170 to 250 years old, taking into account its growth rate over time. But since they often gather tubeworms which are way larger, their average lifespans could, therefore, be much more. These tubeworms don’t have a consistent growth rate but grow more when they are younger as evidenced by the growth rings on their external skeletons.

Tubeworms sustain themselves on sulfide and other nutrients found at the seeps. A paper published by the Penn State research team in 2003 says that the tubeworm does not discharge its waste sulfate into the ocean, but down in the soil. This causes sulfide-producing microbes to grow, which in turn could help the tubeworm to live longer. Their long lifespan could also be a result of a lack of solid growing surface in the Gulf of Mexico which is primarily mud-bottomed.

6. Rougheye rockfish

The rougheye rockfish, also called the blackthroat rockfish or blacktip rockfish, belongs to the genus Sebastes, meaning “magnificent” in Greek. It is extremely long-lived, and has been known to reach an age of 205 years.

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Rougheye rockfish aka Sebastes Aleutianus
Image source: wikimedia

This species of rockfish is also called Sebastes aleutianus, after the Aleutians Islands where they were discovered. Today they can be found all along the North Pacific Ocean. Gregor M Calliet, a fish ecologist, discovered that the lifespan of rockfish could be anywhere between 21 years, in the case of most rockfish, to 205 years, in the case of the rougheye rockfish. They are one of the very few animals which are said to be negligibly senescent. According to theorists, it means that there is no decrease in strength or mobility with age, or an increase in death rate with age, or reduced reproduction capabilities with age. Age in fish is usually determined by analyzing growth rings in their ear bones.

In an article published in 1999, John Guerin, Centenarian Rockfish Project Director at Oregon State University, said that the rockfish could have a mechanism which prevents or repairs oxidative damage. His colleague, Dr. David Williams, a biochemist, studied their livers who look for signs of oxidized protein or damaged DNA. The preliminary result showed that the amount of lipid peroxidation in these rockfish was quite less as compared to animals like rats and monkeys.

7. Bowhead whales
A species of baleen whale found in the Arctic is among the longest-living mammals and can live for more than 200 years. However, because of extensive whale hunting, their numbers are very low, and they are categorized as an endangered species.

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Bowhead whale
Image credit: George Brown Goode/wikimedia

A large bowhead whale was caught in Alaska in 2007 which had a piece of a harpoon embedded in it. The harpoon was made sometime between 1879 and 1885 which means the whale was hit somewhere around 1885 to 1890. This information put the age of that whale at approximately 115 to 130 years old! Soon, scientists calculated the ages of other bowhead whales which found one to be 211 years old and others between 135 and 172 years old. This was the first evidence of its long lifespan.

A study published in 2015 mapped its genome. João Pedro de Magalhães, one of the researchers at the University of Liverpool who also authored this study, said that there were changes in the genes of the bowhead. This could be a sign of “improved DNA repair and cell cycle regulation mechanisms to prevent DNA damage accumulation during the life course…” It could answer questions related to its long lifespan and resistance towards cancer. Also, these whales have very few natural predators, allowing them to grow slowly and have a delayed reproductive stage.

8. Giant tortoises

Giant tortoises are reptiles and among the longest-lived animals on the planet, with some of them living for 150 years and more.

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Aldabra Giant Tortoise
Image credit: Yotcmdr/wikimedia

These Aldabra giant tortoises and Galapagos Island tortoises are found in the two tropical islands in Seychelles and Ecuador. The reason they live for so long is because they have a very slow metabolism. The Galapagos tortoise can survive without food or water for a year. Unfortunately, this ability made them a good food source for ships visiting these islands in the 19th century. Since they live on islands, they have been protected from natural predators that are usually found on land. Their large size and thick shells also provide them with ample protection. However, it was very difficult to correctly determine their ages since they usually outlive the people who observe them.

Among the known ones, Adwaita, an Aldabra giant tortoise, was taken from the islands by British sailors who gifted it to Robert Clive. It was then brought to the Calcutta Zoo in 1875 until it died at the age of 255 years in 2006.

Jonathan, an Aldabra giant tortoise, was taken to St. Helena Island in 1882 where it still resides. If the known date of its birth is correct, then it is 185 years old and the oldest known living reptile. Another tortoise, Tu’i Malila was 188 at the time of its death in 1965. It was a radiated tortoise from Madagascar.

9. Red sea urchin

The red sea urchin is a sea animal covered in spines that can live for about 100 to 200 years. They are even thought to be negligibly senescent and seldom die unless they are killed, captured or eaten first.

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Red sea urchin (Strongylocentrotus franciscanus)
Image credit: Taollan82, Kirt L. Onthank/wikimedia

The red sea urchin is mostly found along the shallow coastal waters of the Pacific Ocean. Before studies proved it otherwise, an average lifespan of this sea invertebrate was thought to be only 7 to 15 years. Research published in the U.S Fishery Bulletin in 2003 revealed that these animals are actually very long lived. They grow throughout their lives at a very slow pace. Since they don’t have any distinguishable features other than spines, their age cannot be ascertained with the usual methods, but only by nuclear carbon testing and biochemical methods.

The scientists from Oregon State University and the Lawrence Livermore National Laboratory who undertook the research have discovered that the red sea urchin has a much longer lifespan than most terrestrial or marine animals. They do not exhibit a decrease in functions related to age. Thomas Ebert, a marine zoologist who was one of the authors of the study, is of the opinion that the red sea urchin appears to be “practically immortal.” Some of the largest and oldest specimens they collected from Canadian waters near British Columbia were almost 19 cm in size. According to the calculations done by these scientists, they are 200 or more years old. They are, however, prone to attacks by other predators, diseases, and even fishing.

10. Orange roughy

The orange roughy, or the deep sea, belongs to the slimehead family and is known for its long lifespan of up to 149 years. Unfortunately, many do not live that long because they are not very resilient and have been overfished until recent efforts were made to limit their catch.

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Orange roughy
Image source: wikimedia

The orange roughy is a big, deep-sea fish found in the Western Pacific Ocean, Eastern Atlantic Ocean and the Eastern Pacific Ocean near Chile. These fish have an extremely slow growth rate and reach sexual maturity only after 30 or 40 years of age. A study by Allen H. Andrews, Dianne M. Tracey, and Matthew R. Dunn of the Rhodes University Department of Ichthyology and Fisheries Science was published in the Canadian Journal of Fisheries and Aquatic Sciences. Through an improved lead–radium-dating technique, they discovered that the fish they had put in the older age group were at least 93 years old. Another study determined their age by counting the growth rings on their ear bones which placed them between 125 and 156 years of age.

In 1991, G.E. Fenton from the University of Tasmania, A. Short from the Environmental Radiochemistry Laboratory in Australia, and D.A. Ritz published a paper that confirmed that the average lifespan of an orange roughy is 77 to 149 years through radiometric dating of their ear bones.

Source : unbelievable-facts.com