The Immortal Jellyfish and Other Age-Defying Organisms - Biology Week

ADDITIONAL CONTRIBUTORS Zachary Ehren

By Zachary Ehren

The expected human lifespan has more or less remained constant throughout the last 2,000 years. Disease and lack of healthcare in third world countries creates a rift in the average age a person tends to live compared to those in first world countries, but averages include outliers (such as infant mortality rates) which skew the numbers in a certain direction. If all factors remained the same, most people would live to be around the ripe age of 80. That being said, if people in ancient Greece were able to live as long as we do now, why can’t modern technology develop ways to extend the ages we meet our demise?

Perhaps technology isn’t the answer. The answers that need to be discovered might simply lie in the organisms around us. There are several creatures currently inhabiting the planet that were old enough to rent a car when our grandparents opened their eyes for the first time. There are also others that were alive when our ancestors were hunting woolly mammoths and Neanderthals were roaming around Europe.

Photo courtesy of Wikimedia Commons.

One relatively famous animal that can live nearly as long as the United States has been a country is the giant tortoise. These slow moving creatures, known to be the oldest living vertebrates, live an average of 120 – 200 years. One of the oldest documented tortoises was Harriet, who lived to be 175 years old when she passed away in 2006. Some believe she is one of the specimens recovered by Charles Darwin after his expedition to the Galapagos Islands. As long as these animals live, there has not been a plethora of documentation as to their exact lifespan because they live longer than the people who study them.

Photo courtesy of Wikimedia Commons.

As for mammals, the bowhead whale holds the crown for the longest known lifespan within its class. Dating the exact age for each whale is difficult, but there have been numerous cases of bowheads being spotted carrying harpoons on their backs that are over 100 years old. Most age testing on animals is done through teeth, a body part that bowheads do not possess, so the hunting devices, along with chemical testing in their eyes has led scientists to the conclusion that bowheads live over a century on average. This theory is also encouraged by the fact that the oldest bowhead on record was documented to be at least 211 years old.

One of the most bizarre cases of animal longevity is brought forth by the turritopsis nutricula jellyfish. For those of us that are not scientists, it is also known as the immortal jellyfish, and could easily be considered the James Bond villain of Mother Nature. It is the only species that seems to bypass death altogether. This is not to say that they are invincible; the turritopsis is still susceptible to starvation, disease, or any other physical factors that kill off any other species. However, these jellyfish are unlike any other known creature because of their ability to cycle back and forth between the two life stages that jellyfish experience.

When the turritopsis is first born, it goes through a stage in its life cycle called the polypoid stage (aka immature stage). As it gets older, it then reaches the medusa (mature) stage, where it can reproduce asexually. This is the same life cycles the majority of jellyfish remain in. Turritopsis differs from its cousins by its ability to revert from medusa to polypoid stage and back again, thus creating an endless cycle which could potentially make them a biologically immortal species. At around 4-5 mm in diameter, they might seem harmless enough, but since the turritopsis does not seem to die, they are slowly starting to invade the oceans.

Photo courtesy of Wikimedia Commons.

Another living organism of the waters, the posidonia oceanic, is believed to be the oldest living thing on earth. Studies have found that this sea grass, inhabiting the Mediterranean Sea, is around 100,000 years old and could be up to 200,000. It has been living for this long because it reproduces by asexually cloning itself. As it grows, it continually produces more branches to cover more of the sea, without ever dying. However, this does not make it insusceptible to climate change and human interference, which is slowly lowering the amount of the posidonia oceanic living in this area.

There are many contributing factors that allow Earth’s longest living animals to survive as long as they do. One common similarity is the rate of metabolism.; both the giant tortoise and bowhead whale metabolize food into energy at very slow rates. Studies have shown that animals that process food faster die at younger ages due to the fact that their bodies are working harder to produce energy. Of course, the rate of metabolism doesn’t take into account the age-defying immortal jellyfish or the self-cloning posidonia. Those two organisms have potentially discovered the Fountain of Youth and symbolize evolution at its best, by developing ways to continue living for indefinite periods of time.

It is still a question to be answered, whether or not there is anything we can take away from these organisms for our benefit, but as long as they are still living as long as they do, prolonging our own lives might not be too far from impossible.

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