1. Water bear
Water bear is an eight-legged segmented micro-animal. It is also known as tardigrades. Its biological name is Hypsibiusdujardini. It is very small in size, about 1.5 mm. They can survive in very harsh conditions even at - 272.8°C to 100°C. They can even survive when you cut, or dry or leave them in space. One quality that makes it different is that they can also stop their metabolism for a long time and can survive even in extreme radiation. When they find a favourable condition, then they restart their metabolism to come back to their lives. Their average estimated life span is for a century.
2. Tree Weta
It is also known as Zombie Bugs. The biological names of such bugs are Hemideina sp. These bugs have a special kind of protein in their blood that makes them resilient to freezing. But their heart and brain can die when completely freeze, as they are not that much resilient to freezing. The most surprising thing is that they can be revived although when thawed out. These bugs remain Immortal till predation.
3. Sea Anemone
The biological name of sea anemone is Actiniaria. Although, the average lifespan of Sea Anemone is about a century. But Sea Anemone can live for a long duration in a favourable situation. Do you know that, if their tentacles are cut, and then they can regenerate themselves from tentacles to a new sea anemone? Hence you can say that they are immortal.
4. Red Sea Urchin
The biological name of such species is Mesocentrotus franciscanus. These species are found mostly on the seaweeds in shallow water. These urchins never grow old and even they never stop growing, hence they are termed as immortal. Although the estimated average life span of such species is about two hundred years and more if there is a favourable environmental condition.
Planaria is also known by its biological name as Planaria lovetorva. These species are blessed with an amazing feature that,they can regenerate any of the lost body parts. This is the reason that such species can live for a long time and never gets older until it wants to. There is not any estimation of their life span. They can live for an indefinite period.
Most of you may have heard about jellyfish. Such species are known by their biological names as Turritopsis dohrnii. They are mostly found in the Sea of Japan and the Mediterranean Sea. You will be shocked to know that the jellyfish can go back to their childhood again. Yeah, it means that they can go back to being sexually immature although, after reaching maturity. And this process has no limitation will the jellyfish died of any disease or predation. Hence there is no average life span of such species. They can live for indefinite periods.
Do you know that there is not any sign of deterioration in the hydra with the increase in age? Yeah, this is why they can keep themselves young for a long time or maybe forever. They can regenerate from the divided parts of the body. They continuously divide themselves to regenerate a new hydra and the process doesn’t stop. Hence, the hydra is one of the immortal species that can live forever.
Bdelloids are one of the immortal species that can tolerate any harsh environmental conditions. They can even survive in the high temperature, extremely low temperature and under high pressure. They have another tendency to go in the state of hibernation in an unfavourable condition and they come back when the favourable condition comes back. Due to these many benefits, there are rare chances of them to die. Although the estimated average life span of such species is One hundred Million Years or they are immortal.
Lungfish is known by its biological name as Neoceratodus forsteri. Do you know that the Neoceratodus forsteri is one of the oldest fish species on the planet earth? Yeah, it's true. They are very much different from the other fish species. This fish can also breathe outside of the water. They tend to slow down their metabolism rate and can tolerate the unfavourable condition. They can survive for a long period even without any nutrients. Hence they are one of the immortal fish. The estimated average lifespan of such species is about 100 years and more.
10. Immortal Lobsters
Immortal Lobsters are also known by the name Homarus americanus. It has been found by the scientist that the Lobsters have a special type of enzyme known as telomerase. Telomerase helps them to persist and even increase their fertility. This enzyme also tends to repair the DNAs lost section. Thus the species old cells again convert to a young one. This process helps them to be an immortal species. To find out the average life span of this species is difficult for the scientist. But you can say that it may be about 100 years and more. They can only die by predation.