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Rearing Temperature and Fatty Acid Supplementation Jointly Affect Lipid Fluorescence Polarization and Heat Tolerance in Daphnia.
Physiological and Biochemical Zoology ( IF 1.8 ) Pub Date : 2019-06-11 , DOI: 10.1086/704365
D. Martin-Creuzburg , B. L. Coggins , D. Ebert , L. Y. Yampolsky

The homeoviscous adaptation hypothesis states that the relative abundance of polyunsaturated fatty acids (PUFAs) in membrane phospholipids of ectothermic organisms decreases with increasing temperatures to maintain vital membrane properties. We reared Daphnia magna at 15°, 20°, and 25°C and increasing dietary concentrations of the long-chain PUFA eicosapentaenoic acid (EPA) to test the hypothesis that the well-documented increase in heat tolerance of high-temperature-reared Daphnia is due to a reduction in body PUFA concentrations. Heat tolerance was assessed by measuring the time to immobility at a lethally high temperature (T imm at 37°C), and whole body lipid fluorescence polarization (FP) was used as an estimate of membrane fluidity. At all rearing temperatures, EPA supplementation resulted in an increase in the relative abundance of EPA in body tissues, but only at 15° and 25°C did this result in a decrease in heat tolerance, and only at 20°C was this associated with an increase in membrane fluidity (i.e., decrease in FP). Overall, however, the degree of tissue fatty acid unsaturation correlated well with heat tolerance and FP. Our results support the homeoviscous adaptation hypothesis by showing that cold-reared Daphnia accumulate PUFAs within their body tissues and thus are more susceptible to heat than hot-reared Daphnia accumulating fewer PUFAs. However, our data also point out that further studies are required that elucidate the complex relationships between PUFA supply, membrane fluidity, and heat tolerance in ectotherms.

中文翻译:

饲养温度和脂肪酸补充共同影响水蚤的脂质荧光极化和耐热性。

顺势而变的适应假说指出,随着温度升高,维持维持重要的膜特性,在外热生物的膜磷脂中多不饱和脂肪酸(PUFA)的相对丰度降低。我们在15°,20°和25°C下饲养了大型水蚤,并增加了日粮中长链PUFA二十碳五烯酸(EPA)的浓度,以检验以下假设:充分记录的高温饲养水蚤的耐热性增加是由于体内PUFA浓度降低。通过测量在致死高温下(37°C时的T imm)达到不动的时间来评估耐热性,并使用全身脂质荧光极化(FP)作为膜流动性的估计值。在所有饲养温度下 补充EPA会增加人体组织中EPA的相对丰度,但是仅在15°C和25°C时,这会导致耐热性降低,只有在20°C时,这才与膜流动性增加相关(即FP减少)。但是,总的来说,组织脂肪酸不饱和度与耐热性和FP密切相关。我们的结果通过显示冷饲养的水蚤在其体内组织中积累PUFA,因此比热饲养的水蚤积累较少的PUFA更容易受到热的影响。但是,我们的数据还指出,需要进一步研究阐明PUFA供应,膜流动性和等温线耐热性之间的复杂关系。但是仅在15°C和25°C时,这会导致耐热性降低,而仅在20°C时,才与膜流动性的提高(即FP的降低)相关。但是,总的来说,组织脂肪酸不饱和度与耐热性和FP密切相关。我们的结果通过显示冷饲养的水蚤在其体内组织中积累PUFA,因此比热饲养的水蚤积累较少的PUFA更容易受到热的影响。但是,我们的数据还指出,需要进一步研究阐明PUFA供应,膜流动性和等温线耐热性之间的复杂关系。但是仅在15°C和25°C时,这会导致耐热性降低,而仅在20°C,这才与膜流动性的增加(即FP的降低)相关。但是,总的来说,组织脂肪酸不饱和度与耐热性和FP密切相关。我们的结果通过显示冷饲养的水蚤在其体内组织中积累PUFA,因此比热饲养的水蚤积累较少的PUFA更容易受到热的影响。但是,我们的数据还指出,需要进一步研究阐明PUFA供应,膜流动性和等温线耐热性之间的复杂关系。组织脂肪酸不饱和度与耐热性和FP密切相关。我们的结果通过显示冷饲养的水蚤在其体内组织中积累PUFA,因此比热饲养的水蚤积累较少的PUFA更容易受到热的影响。但是,我们的数据还指出,需要进一步研究阐明PUFA供应,膜流动性和等温线耐热性之间的复杂关系。组织脂肪酸不饱和度与耐热性和FP密切相关。我们的结果通过显示冷饲养的水蚤在其体内组织中积累PUFA,因此比热饲养的水蚤积累较少的PUFA更容易受到热的影响。但是,我们的数据还指出,需要进一步研究阐明PUFA供应,膜流动性和等温线耐热性之间的复杂关系。
更新日期:2019-11-01
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