Animals / Life

Are there any immortal animals?

Interesting question right? I mean, immortality is an age-old concept. Mythology as old as human history refers to people and animals who never die. But, for the most part, immortality is a fantasy, right?

Well, right. Sort of. Surprisingly, I recently read that there are some animal species that, for whatever reason, have simply decided that they don’t like the idea of death and that they will have no part in it. These animals are “functionally immortal”. Meaning they never age, and unless an outside force does them in they could theoretically live forever. Here were two animals that I found was the most interesting:

Aldabra giant tortoises are exactly what they sound like, giant. From reading an article about these guys, I found that males can weigh nearly 800 pounds, which would make them the most terrifying animals in the world if they ate meat and moved a little quicker. Fortunately, Aldabra tortoises barely seem to notice humans like us, they aren’t tame; they simply don’t care. Because, inside their little reptilian brains, they are laughing at the fact that we get old and die. We aren’t sure just how long Aldabra tortoises live, because they have a pesky tendency to live longer than the people watching them. The oldest confirmed age of an Aldabra tortoise was 255 years, but some may have lived to be twice that age.

Next is the hydra, (and no, its not the several headed dragon) the hydra is a nearly microscopic immortal animal, but what it lacks in size it makes up for in stamina. Hydras are actually remarkably efficient predators; they release an explosion of neurotoxins into their prey, paralyze it, and then consume the animal whole. Here’s the interesting thing to me, every single cell in the hydra’s tiny body is constantly dividing and rejuvenating, so any injured, polluted or defective cells are diluted by the thousands of others. Because they are constantly replenishing their living cells, hydras do not age at all.

One theory as to the cause of human aging is the progressive loss of stem cells.  Tissue in the body can recover from damage, be it internal or external, through the generation of  fresh new cells from division of stem cells residing in niches in those tissues.  However with advancing age, eventually these stem cell niches become depleted and the organism, in this case people, reach the end of life.

In a recent study, researchers looked to find which genes in hydra are responsible for a never ending supply of stem cells and they discovered this characteristic depends specifically on a gene called FoxO, a fork-head box O transcription factor.  In other words, this gene is a master genetic switch that when active allows for the expression of many genes involved in cell cycling.

When FoxO activity was reduced in hydra they exhibited signs of aging and cell senescence. These findings became quite interesting because it had already been shown that a FoxO gene is involved in human aging as well. There is a specific variant of the FoxO3 a human gene that has been linked to extreme human lifespan. So could we live to be as old as the aldabra giant tortoise? One day, maybe.

Your Thoughts?


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