Animal Science

Is immortality real? Observing the creatures that never die from natural causes.

Rezanur Rahman Howlader

What are the first things that come to your mind when you hear the term immortality? Do you think about the mystical creature from Greco –Roman empire, or you think about the giant water snake with nine heads that is known as a hydra? 

Whatever you might think about animal immortality, scientists find evidence of some real-life creature that cannot die from natural causes. However, such kinds of creatures can die by external attack, diseases, etc.  

First of all, we have to understand the scientific reason behind the natural cause of death. Every living creature on earth has a cell death program. Programmed cell death is an effective way for living organisms to eliminate foreign or harmful, or dangerous cells, such as viruses or cancer cells. The old cells are replaced by new cells that are identical to the old ones. 

However, at some point, cell division slows and ends. Telomeres, which are found at the ends of chromosomes, are most likely to blame. If cell division removes these protective caps, cell division will finally no longer be formed. Then new cells will no longer be added, and old cells will die. 

Biologically every living creature has a specific limit to functions in this program for maximum years. For example, the human body has functions only for 120 years, but there are particular creatures which said to be immortal and live forever if there is no external attack such as catastrophe or diseases.

 Immortal Animals That Can Live Forever

Backward aging jellyfish

A small range of jellyfish, known as Turritopsis, or more often known as immortal jellyfish   According to National Geographic, has found a means to defy death by actually reversing its aging process. If the jellyfish is injured or ill, it returns over three days to its polyping stage, converting its cells into a new, eventually adult condition.


There is one animal that may be referred to as immortal. One such animal is the hydra. 

Hydras are tiny, simple freshwater organisms that reproduce asexually by developing clones of themselves and have the ability to regenerate – if cut apart, each piece develops into a new hydra. Their cells divide endlessly, yet they do not age. For precisely that reason, they are also becoming a model for maturity studies.

Red sea urchins

The lifespan of sea urchins varies a lot – some are short-lived, survive four years, some live up to 50, yet some are exceptionally long-lived. Some of the most important examples of Red Sea urchins can survive for hundred years with the ability to regenerate and replicate damaged annexes throughout their lives. 

The extraordinary ability has been found by scientists employing field-based tagging studies to follow individuals and analyze radiocarbons.

Planarian worm: 

Planarians can be split, and each portion can regenerate into an entire organism. The proliferation of cells at the wound site results in the formation of a blastema, which develops into new tissues and regenerates the missing sections of the cut planaria. This characteristic earned them the well-known moniker of being “immortal under the edge of a knife.” 

New tissues can be formed due to pluripotent stem cells, which can generate all cell types. Adult stem cells are referred to as endoblasts, and they account for 20% or more of the cells in an adult mammal. They are the worm’s sole proliferating cells, and they differentiate into progeny that subsequently replaces older cells.


The lifespan of a tardigrade is unknown; however, tardigrades can pause their metabolism and become immortal (state cryptobiosis). 

Cryptobiosis is a phenomenon in which an organism’s metabolism has entirely halted. It is a wholly inactive state where the animal becomes practically indestructible and immortal. Tardigrades were discovered 2,000 years ago on an ice sheet and resurrected. This type of resilience allows it to suspend not only time but also withstand high temperatures. 

Rezanur Rahman Howlader 

BRAC University 

Biotechnology Program (Mathematics and natural science)


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