Tardigrades are true survivors known to be able to withstand extreme cold, heat, pressure, and radiation. Recently, it has been discovered that the biofluorescence of certain tardigrade species may be behind their ability to withstand intense Ultra-Violet radiation. Biofluorescence, as opposed to bioluminescence (which refers to chemical reactions like the light of a firefly), refers to the absorption of UV light by molecular pigments in an animal that then emit a lower energy light that is visible to the human eye and therefore produces a glowing effect. Functionally, it appears that this process also helps defend these little creatures from the damaging effects of UV exposure, acting almost like a colorful sunscreen!
Sketch by Kirsten Sheehy. Fact by Adrian Perez.
Source: Suma, H.R., Prakash, S. and Eswarappa, S.M., 2020. Naturally occurring fluorescence protects the eutardigrade Paramacrobiotus sp. from ultraviolet radiation. Biology Letters, 16(10), p.20200391.