Ultraviolet radiation (UVR) exposure has potentially hazardous effects on aquatic life, even more in the southern hemisphere, which is close to ozone layer depletion. Aquatic animals living in shallow water cannot escape from UVR effects swimming down, so they have to generate other traits to confront it (i.e., enzymes or pigments). Daphnia is a worldwide freshwater genus that inhabits ponds and lakes. Daphnia dadayana inhabits shallow lakes in Patagonia presenting a yellowish carapace and a horn‐like structure in juveniles assumed for avoiding invertebrate predator attacks. We aimed to determine the effect of UVR exposure on the accumulation of melanin and if the development of the antipredatory defense affects the antioxidant response (glutathione S‐transferase [GST] activity) to UVR. We carried out laboratory experiments with treatments with and without UVR exposure measuring melanin accumulation by photographic analyses. Also, we performed an experiment to generate the antipredatory structure exposing D. dadayana indirectly to the predaceous copepod Parabroteas sarsi. Our results showed that UVR increased melanin accumulation in D. dadayana and that the morphological structure against predators did not decrease the antioxidant enzymatic defenses (GST). Our concluding remarks are that D. dadayana is a successful organism that can use its phenotypic plasticity to cope with environmental stressors such as invertebrate predators and UVR exposure with no trade‐off between these two stressors.

中文翻译：

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紫外线照射下水蚤的黑色素和抗掠食性防御

紫外线（UVR）暴露会对水生生物造成潜在的危险影响，在接近臭氧层耗竭的南半球，危害更大。生活在浅水中的水生动物无法逃脱向下游泳的UVR效应，因此它们必须产生其他特征来应对它（即酶或色素）。水蚤是一种世界性的淡水属，栖息于池塘和湖泊中。水蚤栖息在巴塔哥尼亚的浅湖中，这些幼鱼呈现出淡黄色的甲壳和类似角的结构，被认为是为了避免无脊椎动物的食肉动物袭击。我们旨在确定UVR暴露对黑色素积累的影响，以及抗掠食性防御的发展是否会影响对UVR的抗氧化反应（谷胱甘肽S-转移酶[GST]活性）。我们进行了带有或不带有紫外线照射的处理的实验室实验，通过照相分析来测量黑色素的积累。此外，我们进行了一项实验，以产生反捕食性结构，将D. dadayana间接暴露于早ace足的pe足类Parabroteas sarsi中。我们的结果表明，UVR增加了黄D中黑色素的积累。且针对捕食者的形态结构并未降低抗氧化酶防御能力（​​GST）。我们的结论是，D。dadayana是一种成功的生物，可以利用其表型可塑性来应对环境应激源，例如无脊椎动物掠食性动物和UVR暴露，而这两个应激源之间没有权衡取舍。