Earth’s toughest creature is even more resilient

Earth’s toughest creature is even more resilient
Oct 16 (Agencies) | Publish Date: 10/16/2020 12:41:37 PM IST

 Earth’s toughest creatures — the tiny tardigrades — include species that can survive deadly UV radiation by glowing in the dark, a study has found.

Tardigrades — also known as ‘moss piglets’, or ‘water bears’ — are bizarre, microscopic water-dwelling animals capable of surviving in extreme environments.

They can tolerate heats of 300°F (150°C) to the coldness of space, dry out and revive years later and stand pressures six times those found in the Mariana Trench.

And a study last year revealed that the resilient little critters can even survive the equivalent amount of nuclear radiation as 25 hours at Chernobyl’s ground zero.

However, researchers from India have reported finding a new genus — dubbed ‘Paramacrobiotus’ — which can also resist germicidal levels of UV exposure.

It does this by employing a protective fluorescent shield that absorbs the damaging ultraviolet radiation and emits it back out as harmless blue light.

‘Our study showed that specimens of Paramacrobiotus [...] exhibit natural fluorescence under UV light, which protects tardigrades against the lethal doses of UV radiation,’ biochemist Harikumar Suma and colleagues wrote in their paper.

The tiny creature, the team from the Indian Institute of Science explained, ‘has probably evolved this fluorescence mechanism to counter [the] high ultraviolet radiation of tropical southern India — UV index can reach up to 10.’

‘The UV dose in this location — Bengaluru, India — on a typical summer day is about four kilojoules per square metre.’

The tardigrades the team studied were isolated from a moss sample grown on a concrete wall in their home town of Bengaluru.

The researchers found that when they exposed Paramacrobiotus to UV radiation for 15 minutes — enough to kill another tardigrade species, H. exemplaris — the new genus not only survived, but surprisingly emitted a blue glow.

When the team coated H. exemplaris and the roundworm, ‘Caenorhabditis elegans’ in fluorescent extracts from Paramacrobiotus, they found that they were able to transfer some of the protection.

After a few days of UV exposure, half of the treated H. exemplaris remained alive despite having been given a dose that should have been lethal.

The study adds to previous work showing that substances produced by tardigrades have the potential to protect other organisms from harmful conditions, biologist Łukasz Kaczmarek — who was not involved in the work — told the Guardian.

The expert from Poland’s Adam Mickiewicz University added, however, that the team had not identified the exact substance responsible for the UV protection, raising the possibility that protective proteins — not the fluorescence — might be responsible. 

‘We also do not know if it is a characteristic feature of the species studied or rather for the majority of tardigrades exposed in their natural environment to high doses of UV radiation,’ Dr Kaczmarek told the Guardian. 



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