Hansson Lars-Anders, Hylander Samuel, Sommaruga Ruben
Institute of Ecology/Limnology, Lund University, Lund SE-223 62 Sweden.
Ecology. 2007 Aug;88(8):1932-9. doi: 10.1890/06-2038.1.
In order to avoid environmental threats, organisms may respond by altering behavior or phenotype. Using experiments performed in high-latitude Siberia and in temperate Sweden, we show for the first time that, among freshwater crustacean zooplankton, the defense against threats from ultraviolet radiation (UV) is a system where phenotypic plasticity and behavioral escape mechanisms function as complementary traits. Freshwater copepods relied mainly on accumulating protective pigments when exposed to UV radiation, but Daphnia showed strong behavioral responses. Pigment levels for both Daphnia and copepods were generally higher at higher latitudes, mirroring different UV threat levels. When released from the UV threat, Daphnia rapidly reduced (within 10 days) their UV protecting pigmentation-by as much as 40%--suggesting a cost in maintaining UV protective pigmentation. The evolutionary advantage of protective pigments is, likely, the ability to utilize the whole water column during daytime; conversely, since the amount of algal food is generally higher in surface waters, unpigmented individuals are restricted to a less preferred feeding habitat in deeper waters. Our main conclusion is that different zooplankton taxa, and similar taxa at different latitudes, use different mixes of behavior and pigments to respond to UV radiation.
为了避免环境威胁，生物体可能会通过改变行为或表型来做出反应。通过在高纬度西伯利亚和温带瑞典进行的实验，我们首次表明，在淡水甲壳类浮游动物中，抵御紫外线（UV）威胁的是一个表型可塑性和行为逃避机制作为互补特征发挥作用的系统。淡水桡足类动物在受到紫外线辐射时主要依靠积累保护性色素，但水蚤表现出强烈的行为反应。水蚤和桡足类动物的色素水平在较高纬度地区通常更高，这反映了不同的紫外线威胁水平。当从紫外线威胁中解脱出来时，水蚤会迅速（在10天内）减少其紫外线防护色素沉着——多达40%——这表明维持紫外线防护色素沉着存在成本。保护性色素的进化优势可能在于白天能够利用整个水柱；相反，由于表层水域的藻类食物通常较多，未带色素的个体被限制在较深水域不太适宜的觅食栖息地。我们的主要结论是，不同的浮游动物类群，以及不同纬度的相似类群，会使用不同的行为和色素组合来应对紫外线辐射。
