Humboldt-Universität zu Berlin, Department of Biology, Laboratory of Freshwater and Stress Ecology, Arboretum, 12437 Berlin, Germany.
Chemosphere. 2013 Feb;90(7):2136-41. doi: 10.1016/j.chemosphere.2012.10.099. Epub 2012 Dec 1.
For organisms, temperature is one of the most important environmental factors and gains increasing importance due to global warming, since increasing temperatures may pose organisms close to their environmental tolerance limits and, thus, they may become more vulnerable to environmental stressors. We analyzed the temperature-dependence of the water-soluble antioxidant capacity of the cladoceran Moina macrocopa and evaluated its life trait variables with temperature (15, 20, 25, 30°C) and humic substance (HS) concentrations (0, 0.18, 0.36, 0.90, 1.79 mM DOC) as stressors. Temperatures below and above the apparent optimum (20°C) reduced the antioxidative capacity. Additions of HSs increased body length, but decreased mean lifespan at 15 and 20°C. There was no clear HS-effect on offspring numbers at 15, 20, and 30°C. At 25°C with increasing HS-concentration, lifespan was extended and offspring numbers increased tremendously, reaching 250% of the control. Although the applied HS preparation possesses estrogenic and antiandrogenic activities, a xenohormone mechanism does not seem plausible for the reproductive increase, because comparable effects did not occur at other temperatures. A more convincing explanation appears to be the mitohormesis hypothesis which states that a certain increase of reactive oxygen production leads to improved health and longevity and, with Moina, also to increased offspring numbers. Our results suggest that at least with the eurythermic M. macrocopa, a temperature above the optimum can be beneficial for several life trait variables, even when combined with a chemical stressor. Temperatures approximately 10°C above its optimum appear to adversely affect the lifespan and reproduction of M. macrocopa. This indicates that this cladoceran species seems to be able to utilize temperature as an ecological resource in a range slightly above its thermal optimum.
对于生物体而言，温度是最重要的环境因素之一，由于全球变暖，温度的升高可能使生物接近其环境耐受极限，从而使它们更容易受到环境胁迫的影响。我们分析了枝角类动物大型溞的水溶性抗氧化能力对温度的依赖性，并评估了其在温度（15、20、25、30°C）和腐殖质（HS）浓度（0、0.18、0.36、0.90、1.79 mM DOC）作为胁迫因素时的生命特征变量。在明显最佳温度（20°C）以下和以上，抗氧化能力会降低。HS 的添加增加了体长，但降低了在 15 和 20°C 时的平均寿命。在 15、20 和 30°C 时，HS 对后代数量没有明显的影响。在 25°C 时，随着 HS 浓度的增加，寿命延长，后代数量急剧增加，达到对照的 250%。尽管所应用的 HS 制剂具有雌激素和抗雄激素活性，但由于在其他温度下没有发生类似的效果，因此，生殖增加的异种激素机制似乎不太可能。一个更有说服力的解释似乎是线粒体激素假说，该假说指出，一定程度的活性氧产生增加会导致健康和寿命的提高，而对于大型溞，也会导致后代数量的增加。我们的结果表明，至少对于广温性的大型溞而言，在最佳温度以上的温度对几个生命特征变量都是有益的，即使与化学胁迫因素结合也是如此。最佳温度以上约 10°C 的温度似乎会对大型溞的寿命和繁殖产生不利影响。这表明这种枝角类动物物种似乎能够在略微高于其热最佳温度的范围内将温度用作生态资源。
