Why do some animals live longer than us? Or shorter?
Life expectancy varies for us, but also for animals. Among humans, the world record for lifespan is held by Jeanne Calment, who died on August 4, 1997, in Arles (Bouches-du-Rhône) at the age of 122 years, 5 months, and 14 days. But not everyone on the planet lives to be 122 years old.
Simon Galas, University of Montpellier and Myriam Richaud, University of Montpellier
As early as 1982, while studying a small worm measuring 1 mm in length Caenorhabditis elegans, scientists were able to measure that genes were responsible for 20 to 50% of longevity. Later, it was observed that a person's lifespan is controlled by about one-third by the genes inherited from their parents. In France, the current life expectancy is 85 years for women and 79 years for men.
But lifespan also varies among animals that break records. Their lifespan may be even more elastic than ours, as if we compare the lifespan of a mouse (4 years) with that of a bat (24 years), even though they are not very different. A small worm 2 mm long (Strongyloides ratti does even better. Its lifespan is 5 days when it lives in clumps of earth, but 403 days when it parasitizes small mammals. A very, very flexible elastic band!
But there's more. In 1868, an oceanographic expedition around Iceland captured a clam (Arctia islandica), which was determined in 2005 to be 374 years old, and recently 507 years old in other individuals.
An animal that is 11,000 years old!
Still at the bottom of the sea, the glass sponge (Monoraphis chuni) was discovered in 1996 at a depth of 1,110 meters in the China Sea, south of Japan. This sponge produces a kind of fiberglass (silica) rod, which enabled researchers to determine in 1986 that it was 11,000 years old!
There are therefore animals that can live much longer than us, and from these two examples, we can see that they are often marine animals. But there are also animals that live for a very short time, such as mayflies, which fly for only a few days, or the great peacock moth, whose life span does not exceed a week. These two insects share a curious trait: they do not have the apparatus to feed themselves and are therefore programmed to live for a very short time.
Some animals are also known for their ability to rejuvenate and live even longer. This is the case with the tiny 5 mm sea jellyfish Turritopsis , which is capable of rejuvenating all the cells in its body and reverting to a baby jellyfish at will, while the hydra (Hydra vulgaris), which lives in fresh water, is capable of renewing all the cells in its body. It has been impossible to observe the end of this animal's normal life.
Sometimes, animals can revive after a very long period of slowed life during which thethe animal stops all its vital functions and sometimes becomes completely dehydrated, for example, tardigrades collected in Antarctica and awakened after a 30-year sleep, or small nematode worms hidden in squirrel holes under the frozen ground of Siberia that were awakened after 42,000 years.
As we can see, there are animals that can live for a very short time compared to us, while others live much longer. Scientists study these animals to try to understand how they function and what controls their lifespan.
How can this variability in life expectancy be explained?
Several explanations have been proposed to account for these large differences in lifespan. Scientists believe that some animals use systems that allow their cells to remain functional for longer without aging, such as shellfish and glass sponges, while others use their ability to rejuvenate their cells at will, such as small jellyfish and freshwater hydras, to avoid dying.
And what about us? There is some good news, though. Even though we can't rejuvenate ourselves at will like some animals, scientists have discovered that we do so every time we have babies.
To produce our reproductive cells (eggs and sperm), our bodies have found a way to force some of our cells to become very, very young again. It is from these cells (germ cells) that a woman will produce eggs and a man will produce sperm that are no longer their age but much younger. It's like going back in time, as jellyfish and hydras do, but in our case it only happens at the moment of reproduction, and that's what allows us to have babies who are not the same age as their parents at birth, but simply their own age instead.
If you have a question too, ask your parents to send an email to: rf.no1769572766itasr1769572766evnoc1769572766eht@r1769572766oinuj1769572766ct1769572766. We will find a scientist to answer your question.
Simon Galas, Professor of Genetics and Molecular Biology of Aging, IBMM CNRS UMR 5247 – Faculty of Pharmacy, University of Montpellier and Myriam Richaud, Doctor of Genetics and Molecular Biology of Aging, Faculty of Pharmacy, University of Montpellier
This article is republished from The Conversation under a Creative Commons license. Readthe original article.