Hird Coen, Cramp Rebecca L, Franklin Craig E
School of the Environment, The University of Queensland, Magandjin, 4072, Australia.
School of the Environment, The University of Queensland, Magandjin, 4072, Australia.
J Therm Biol. 2023 Oct;117:103711. doi: 10.1016/j.jtherbio.2023.103711. Epub 2023 Sep 13.
Increases in ultraviolet radiation (UVR) correlate spatially and temporally with global amphibian population declines and interact with other stressors such as disease and temperature. Declines have largely occurred in high-altitude areas associated with greater UVR and cooler temperatures. UVR is a powerful mutagenic harming organisms largely by damaging DNA. When acutely exposed to UVR at cool temperatures, amphibian larvae have increased levels of DNA damage. Amphibians may compensate for the depressive effects of temperature on DNA damage through acclimatisation, but it is unknown whether they have this capacity. We reared striped marsh frog larvae (Limnodynastes peronii) in warm (25 °C) and cool (15 °C) temperatures under a low or moderate daily dose of UVR (10 and 40 μW cm UV-B for 1 h at midday, respectively) for 18-20 days and then measured DNA damage resulting from an acute high UVR dose (80 μW cm UV-B for 1.5 h) at a range of temperatures (10, 15, 20, 25, and 30 °C). Larvae acclimated to 15 °C and exposed to UVR at 15 °C completely compensated UVR-induced DNA damage compared with 25 °C acclimated larvae exposed to UVR at 25 °C. Additionally, warm-acclimated larvae had higher DNA damage than cold-acclimated larvae across test temperatures, which indicated a cost of living in warmer temperatures. Larvae reared under elevated UVR levels showed no evidence of UVR acclimation resulting in lower DNA damage following high UVR exposure. Our finding that thermal acclimation in L. peronii larvae compensated UVR-induced DNA damage at low temperatures suggested that aquatic ectotherms living in cool temperatures may be more resilient to high UVR than previously realised. We suggested individuals or species with less capacity for thermal acclimation of DNA repair mechanisms may be more at risk if exposed to changing thermal and UVR exposure regimes.
紫外线辐射（UVR）的增加在空间和时间上与全球两栖动物种群数量下降相关，并与疾病和温度等其他压力源相互作用。种群数量下降主要发生在与更高UVR和更低温度相关的高海拔地区。UVR是一种强大的诱变剂，主要通过损伤DNA来伤害生物体。当在低温下急性暴露于UVR时，两栖动物幼体的DNA损伤水平会增加。两栖动物可能通过适应来补偿温度对DNA损伤的抑制作用，但它们是否具有这种能力尚不清楚。我们将条纹沼蛙幼体（Limnodynastes peronii）在温暖（25°C）和凉爽（15°C）的温度下，分别以低或中等每日剂量的UVR（中午分别为10和40μW/cm UV-B照射1小时）饲养18 - 20天，然后在一系列温度（10、15、20、25和30°C）下测量急性高剂量UVR（80μW/cm UV-B照射1.5小时）导致的DNA损伤。与在25°C适应并在25°C暴露于UVR的幼体相比，适应15°C并在15°C暴露于UVR的幼体完全补偿了UVR诱导的DNA损伤。此外，在所有测试温度下，温暖适应的幼体比寒冷适应的幼体具有更高的DNA损伤，这表明生活在较高温度下存在代价。在较高UVR水平下饲养的幼体没有显示出UVR适应的证据，即在高UVR暴露后导致更低的DNA损伤。我们的发现表明，条纹沼蛙幼体的热适应在低温下补偿了UVR诱导的DNA损伤，这表明生活在凉爽温度下的水生变温动物可能比以前意识到的更能抵御高UVR。我们认为，如果暴露于不断变化的温度和UVR暴露模式下，DNA修复机制热适应能力较弱的个体或物种可能面临更大风险。
