Naturally occurring fluorescence has been observed in multiple species ranging from bacteria to birds. In macroscopic animals such as birds, fluorescence provides a visual communication signal. However, the functional significance of this phenomenon is unknown in most cases. Though photoprotection is attributed to fluorescence under ultraviolet (UV) light in some organisms, it lacks direct experimental evidence. Here, we demonstrate naturally occurring fluorescence under UV light in a eutardigrade belonging to the genus Paramacrobiotus. Using a natural variant that lacks fluorescence, we show that the fluorescence confers tolerance to lethal UV radiation. Remarkably, the fluorescent extract from Paramacrobiotus sp. could protect the UV-sensitive tardigrade Hypsibius exemplaris and nematode Caenorhabditis elegans from germicidal UV radiation. We propose that Paramacrobiotus sp. possess a protective fluorescent shield that absorbs harmful UV radiation and emits harmless blue light.

在从细菌到鸟类的多种物种中都观察到了自然发生的荧光。在鸟类等宏观动物中，荧光提供了视觉交流信号。然而，在大多数情况下，这种现象的功能意义是未知的。尽管某些生物体中的光保护作用归因于紫外 (UV) 光下的荧光，但缺乏直接的实验证据。在这里，我们展示了在属于Paramacrobiotus属的eutardigrade 中在紫外线下自然发生的荧光。使用缺乏荧光的天然变体，我们表明荧光赋予对致命紫外线辐射的耐受性。值得注意的是，来自Paramacrobiotus sp.的荧光提取物。可以保护对紫外线敏感的缓步动物来自杀菌紫外线辐射的Hypsibius exemplaris和线虫秀丽隐杆线虫。我们建议Paramacrobiotus sp。拥有保护性荧光屏，可以吸收有害的紫外线辐射并发出无害的蓝光。