It’s been said that the tardigrade, an eight-legged microscopic creature –the most resilient form of life on our planet, that can exist for up to 30 years without food or water and endure temperature extremes up to 150 degrees Celsius– will exist until the Sun dies.
“They are as indestructible as it gets on Earth,” reports an Oxford University collaboration, “and is likely to survive all astrophysical calamities such as as asteroid impact, supernova explosion or gamma ray bursts. “but it’s possible that there are other resilient species elsewhere in the universe. There is a real case for looking to Mars and other areas of our solar system. If tardigrades are Earth’s most resilient species, who knows what else is out there.”
Will Exist Long After Humans are Gone
“Without our technology protecting us, humans are a very sensitive species,” said Rafael Alves Batista, astrophysicist at Oxford University. “Subtle changes in our environment impact us dramatically. There are many more resilient species on Earth. Life on this planet can continue long after humans are gone.”
A study published in Nature, The Resilience of Life to Astrophysical Events, has shown that the water-dwelling tardigrades can live up to 60 years. It will survive the risk of extinction from all astrophysical catastrophes and will exist for at least 10 billion years –far longer than the human species, implying thta life on Earth will extend as long as the Sun keeps shining. It also reveals that once life emerges, it is surprisingly resilient and difficult to destroy, extending the possibility of life on other planets.
Organisms with similar tolerances to radiation and temperature could survive long term below the surface. “It is difficult to eliminate all forms of life from a habitable planet, said Harvard astrophysicist and co-author, Avi Loeb. The subsurface oceans of Europa and Enceladus could have conditions similar to the deep oceans of Earth, where tardigrades, also known as water bears, are found, with volcanic vents providing heat in an environment devoid of light. The discovery of extremophiles is such locations would be a significant step forward in bracketing the range of conditions for life to exist on planets around other stars,” adds Loeb.
“A New Species?” –Can Survive Intense Ultraviolet Radiation
A tiny tardigrade can survive intense ultraviolet radiation for an hour by glowing in the dark and can turn into glass to survive complete dehydration. “It acts like a shield,” says Sandeep Eswarappa at the Indian Institute of Science in Bangalore, about the 1 millimeter long creature. Studying moss at their institute’s campus, Eswarappa and his colleagues found what may be a new species of tardigrade, though they don’t yet have enough information to formally describe it. For now, they are calling it Paramacrobiotus BLR, short for Bangalore.
“We found this particular tardigrade in many places, especially in places that are well lit with sunlight,” says Eswarappa. The researchers transferred some of the animals to their laboratory and began to study them.
The Glow –Acts as a Shield
Their first experiment involved exposing the animals to a germicidal ultraviolet lamp. A control animal, a worm called Caenorhabditis elegans, died within 5 minutes, but Paramacrobiotus BLR survived for an hour. “The next step happened serendipitously,” says Eswarappa. While looking at how the tardigrades might survive the UV light, he left a tube of them near a UV source and noticed that the tube started glowing.
Contain a Fluorescent Chemical
Further experiments revealed that the tardigrades contain a fluorescent chemical. “It is absorbing the UV light and emitting harmless visible light in the blue range,” says Eswarappa. The team was able to transfer the fluorescent chemical to another tardigrade, Hypsibius exemplaris, and to C. elegans, both of which are sensitive to ultraviolet radiation. This protected them from 15 minutes of UV exposure.
The team doesn’t yet know exactly what makes up the fluorescent shield, as simple methods for identifying the chemicals haven’t yielded clear results. “It is not a simple compound,” says Eswarappa.
Image credit top of page: Shutterstock License; text, tardigrade using fluorescence to resist lethal UV radiation
Harikumar R Suma & Sandeep M Eswarappa