The tardigrades are able to overcome cryptobiosis, the suspension of metabolic processes, and tolerate periods of dehydration up to ten years. In addition, they withstand extreme temperatures and survive in a vacuum or under conditions of abnormal pressure.
Indian researchers claim to have found a new species of tardigrade, also known as water bears, with an unexpected protective superpower: they can survive ultraviolet radiation. These microorganisms were discovered in a sample of moss on a concrete wall in the city of Bangalor, India.
During the study, published in the scientific journal Biology Letter, scientists proved the existence of the new species, called Paramacrobiotus BLR. The researchers found that the strain survived the levels of ultraviolet radiation that are enough to kill in just 24 hours another species of less resistant tardigrade and that is generally used in experiments, known as H. exemplaris.
CC BY-SA 3.0 / Bob Goldstein e Vicky Madden, UNC Chapel Hill
Normally, ultraviolet radiation can damage DNA, tearing it apart and causing cells to die. But Paramacrobiotus BLR survived that radiation for 30 days.
According to the researchers, the discovery of the fluorescent shield was accidental. While studying these creatures in ultraviolet light, they noticed that the test tubes filled with Paramacrobiotus BLR glowed or “fluoresced”, which was not the case with tubes with H. exemplaris. Therefore, the scientists concluded that fluorescence could protect microorganisms from the harmful effects of ultraviolet radiation.
To test this hypothesis, the researchers mixed 300 specimens with a little water in a paper mill. The resulting solution contained the chemicals apparently used by Paramacrobiotus BLR as an ultraviolet shield.
The scientists added this solution to a plate that contained microscopic worms and H. exemplaris tardigrades to determine whether it provides a protective effect. Worms and tardigrades showed higher survival rates after ultraviolet radiation that would normally kill them.
The fluorescent chemical compound that Paramacrobiotus BLR uses as a shield has not yet been determined. The research group thinks the tardigrade may have developed its fluorescent shield to combat the high levels of radiation that exist in southern India.