Examples of Animal Resilience and Extreme Adaptations

Introduction

The Earth is currently the only known planet to harbour life. With over 8.7 million species discovered till now, there are a few animals and plants that display incredible acts of resilience. From immortality and extreme radiation resistance to infrared vision and surviving the vacuum of space, here are a few incredibly resilient animals you should know about.

Snakes – Infrared Sensing

The ability to see infrared radiation is well portrayed in certain movies. However, two groups of snakes – Pit vipers and pythons have the ability to sense infrared thermal radiation. This is accomplished with the help of a special organ called the Pit Organ that allows it to essentially “see” at wavelengths between 5μm and 30μm. On pit vipers, this sense is, even more, evolved, and enables it to strike prey accurately in the absence of light. Some scientists speculate that this organ evolved for hunting prey while others argue that it is used in thermoregulation.

Turritopsis Dohrnii, The Immortal Jellyfish

Turritopsis Dohrnii is a jellyfish that is less than half a centimetre across. Unlike every other animal on earth, it does not die from ageing. Instead, it reaches full maturity and then reverts back to its polyp stage, restarting its whole life cycle again. If humans had this feature, it would be the equivalent of reaching old age and then, instead of dying, we would revert back to a foetus.

Also Read: Jellyfish Life Cycle

Planaria, The Regenerating Flatworm

Imagine if somebody cut your head off. Then, your decapitated head would regrow a new body and your headless body would regrow a new head – essentially creating a new copy of yourself. This is exactly what Planaria does, a free-living flatworm. This is only possible due to the abundance of stem cells in its body. Scientists have discovered that a fragment as small as 1/279 of the worm can regrow into a new animal in a few weeks.

Also Read: Regeneration in Planaria

Water Bears – Tardigrades

Known by its more scientific name – Tardigrades, these are near-microscopic creatures no larger than a millimetre. They usually dwell at the bottom of lakes and on dry land and are found on mosses. However, some water bears are more extreme than most extremophiles, with specimens being discovered in hot, boiling springs and under layers of dense ice. They’re even found to survive the harsh vacuum of space when scientists sent a few samples of the organism on the outside of a FOTON M3 rocket. Scientists have also reported that they can adapt to extremely harsh conditions by drying up (desiccation) and reducing their metabolism to 0.01% of its normal rate.

Deinococcus Radiodurans – Most Resilient Animal Known To Science

Ionising radiation is the most dangerous form of radiation. If a living organism is exposed to such kind of radiation, one of the following three things may happen:

• The cell dies
• The cell mutates and becomes cancerous
• The cell gets damaged but repairs itself

A high dose of radiation results in the first scenario while the latter two can occur if the dose of radiation is lower. Moreover, nearly all known forms of life are affected if exposed to ionising radiation. However, Deinococcus radiodurans is more like a biological anomaly. It is one of the most radiation-resistant organisms ever known. Moreover, it is a polyextremophile, which means it can also survive the vacuum of space, extreme cold, exposure to acid and also dehydration. This makes this bacterium one of the toughest organisms on earth. Consequently, it has been given the nickname “Conan the Bacterium”. This organism is so resistant to radiation that it can survive an acute dose of 5,000 grays (Gy). In comparison, a dose of 5 Gy can kill a human. Between 200 to 800 Gy is enough to kill E.coli. In fact, this bacterium is even more radiation-resistant than the tardigrades – which can be killed with a dose of more than 4,000 Gy. What makes this organism unique is its ability to repair damaged DNA. As we all are aware, DNA is the building block of life and without this crucial molecule, the body will not be able to repair itself or even grow. Hence, an organism that had its DNA damaged by radiation will be unable to create new cells. This means the organism will eventually die. So how does this bacterium overcome this hurdle? Deinococcus radiodurans has multiple copies of its genome as well as cellular mechanisms which enable rapid repair of its DNA. Moreover, no additional mutations are introduced during the repair process. These adaptations make this bacterium the ideal organism to study the processes that cause cancer and ageing. In conclusion, this is the most resilient animal known to science.

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