Connelly Sandra J, Stoeckel James A, Gitzen Robert A, Williamson Craig E, González Maria J
Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, NY 14623, United States of America.
School of Fisheries, Aquaculture and Aquatic Sciences, College of Agriculture, Auburn University, Auburn, AL 36849, United States of America.
PLoS One. 2016 Jul 19;11(7):e0159628. doi: 10.1371/journal.pone.0159628. eCollection 2016.
Recent studies have demonstrated substantial effects of environmental stress that vary among clones. Exposure to ultraviolet radiation (UV) is an important abiotic stressor that is highly variable in aquatic ecosystems due to diel and seasonal variations in incident sunlight as well as to differences in the UV transparency of water among water bodies, the depth distribution of organisms, and the ability of organisms to detect and respond to UV. In contrast to the convention that all UV is damaging, evidence is accumulating for the beneficial effects of exposure to low levels of UV radiation. Whereas UV has been frequently observed as the primary light-related stressor, herein we present evidence that dark conditions may be similarly "stressful" (reduction of overall fitness), and stress responses vary among clones of the freshwater crustacean Daphnia parvula. We have identified a significant relationship between survivorship and reduced fecundity of clones maintained in dark conditions, but no correlation between tolerance of the clones to dark and UV radiation. Low tolerance to dark conditions can have negative effects not only on accumulated stresses in organisms (e.g. the repair of UV-induced damage in organisms with photolyase), but potentially on the overall physiology and fitness of organisms. Our results support recent evidence of the beneficial effects of low-level UV exposure for some organisms.
最近的研究表明，环境压力的影响很大，且在不同克隆体之间存在差异。紫外线辐射（UV）是一种重要的非生物胁迫因子，在水生生态系统中，由于入射阳光的昼夜和季节变化，以及水体之间紫外线透明度的差异、生物体的深度分布以及生物体检测和响应紫外线的能力，紫外线辐射具有高度变异性。与所有紫外线都具有破坏性的传统观念相反，越来越多的证据表明，暴露于低水平紫外线辐射具有有益影响。虽然紫外线经常被视为主要的光相关胁迫因子，但在此我们提供证据表明，黑暗条件可能同样具有“胁迫性”（降低整体适应性），并且淡水甲壳类动物大型溞的不同克隆体之间的应激反应存在差异。我们已经确定，在黑暗条件下维持的克隆体的存活率与繁殖力降低之间存在显著关系，但克隆体对黑暗和紫外线辐射的耐受性之间没有相关性。对黑暗条件的低耐受性不仅会对生物体中的累积应激产生负面影响（例如，具有光裂解酶的生物体中紫外线诱导损伤的修复），而且可能会对生物体的整体生理和适应性产生负面影响。我们的结果支持了最近关于低水平紫外线暴露对某些生物体有益影响的证据。
