Scientists have found another reason to be impressed tardigrady; some of these microscopic, almost indestructible creatures wear a luminous “shield” that protects them from ultraviolet radiation.
Thin tardigrades – also called moss piglets or water bears – are known for their toughness, able to withstand extreme heat, cold and pressure, as well as the vacuum in space. They can also survive exposure to levels of radiation it would kill many other life forms.
Scientists have now uncovered new clues to the radiation resistance of tardigrades. Experiments with tardigrades in Paramacrobiotus Rod revealed that fluorescence protects them like a layer of sunscreen, turning them into damaging UV rays in harmless blue light, according to a new study.
Connected: 8 reasons why we love tardigrades
Biofluorescence bathes various creatures in an ominous radiance. It differs from bioluminescence, which sparks light through a chemical reaction between compounds in an animal̵
In fluorescent animals, their brightness – usually red or green – is not the result of a chemical reaction. Rather, these animals fluoresce when molecules in their cells absorb light particles or photons from invisible UV rays and emit lower-energy light with a longer wavelength. There is sea turtles with fluorescent shells and heads, and small orange frogs and chameleons with fluorescent bones. Jellyfish glow with fluorescent light as they do scorpions, parrots, nematodes and da – tardigradi, said lead author Sandiip M. Eswarapa, an assistant professor in the Department of Biochemistry at the Indian Institute of Science in Bangalore, India.
Yet little is known about how most fluorescent species use their luster. For the new study, the authors question whether fluorescence in tardigrades may be related to the radiation tolerance of water bears.
“Both phenomena were connected”
Scientists tested Paramacrobiotus resistance to ultraviolet rays, exposing them to 15 minutes of radiation at levels high enough to kill most microorganisms. All from Paramacrobiotus tardigrades were still alive 30 days later while Hipslbius model Tardigrade, which was sensitive to ultraviolet rays, died within 24 hours of radiation exposure, according to the study
“There was no difference in the survival of these two modified species when they were not treated with ultraviolet radiation,” Eswarapa told Live Science in an email.
Paramacrobiotus tardigrades also glow brightly when exposed to UV light. However, when the researchers extracted fluorescent components from Paramacrobiotus tardigrades and apply them to both H. model and the nematode Caenorhabditis elegans – which is also non-fluorescent and sensitive to ultraviolet rays – both species “showed partial tolerance to ultraviolet rays”, the researchers said.
“It was natural to think that both phenomena were related,” Eswarapa said.
Previous research has suggested that biofluorescence may offer UV protection in some corals, and researchers looking for extraterrestrial life have suggested that biofluorescence may help organisms thrive and survive in distant worlds orbiting red dwarf stars – which have more high UV power from our sun – potentially inhabiting planets with many varieties of luminous beings, It was previously reported by Live Science.
For glowing terrestrial tardigrades, fluorescence can increase their chances of surviving in habitats where water bears are often exposed to the sun, Eswarapa said.
“Ultraviolet resistance provides these tarigrades with the ability to thrive in a high UV index. For example, in the tropics,” he said.
The findings were published online on October 13 in the journal Letters on biology.
Originally published in Live Science.