Muñoz-Garcia Agustí, Williams Joseph B
Department of Evolution, Ecology, and Organismal Biology, Aronoff Laboratory, Ohio State University, 318 West 12th Avenue, Columbus, OH 43210, USA.
Proc Natl Acad Sci U S A. 2008 Oct 7;105(40):15611-6. doi: 10.1073/pnas.0805793105. Epub 2008 Oct 6.
Intercellular lipids of the stratum corneum (SC), the outer layer of the epidermis, form a barrier to water vapor diffusion through the skin. Previously, we measured cutaneous water loss (CWL) and lipid composition of the SC of adult house sparrows from two populations, one living in the deserts of Saudi Arabia and another living in mesic Ohio. Adult desert house sparrows had a lower CWL, a lower proportion of free fatty acids, and a higher proportion of ceramides and cerebrosides in the SC compared with mesic sparrows. In this study, we investigated developmental plasticity of CWL and lipid composition of the SC in desert and mesic nestling house sparrows reared in low and high humidity and compared our results with previous work on adults. We measured CWL of nestlings and analyzed the lipid composition of the SC using thin-layer chromatography. We showed that nestling house sparrows from both localities had higher CWL than adults in their natural environment, a result of major modifications of the lipid composition of the SC. The expression of plasticity in CWL seems to be a response to opposed selection pressures, thermoregulation and water conservation, at different life stages, on which regulation of CWL plays a crucial role. Desert nestlings showed a greater degree of plasticity in CWL and lipid composition of the SC than did mesic nestlings, a finding consistent with the idea that organisms exposed to more environmental stress ought to be more plastic than individuals living in more benign environments.
角质层（SC）是表皮的外层，其细胞间脂质形成了一道阻止水蒸气通过皮肤扩散的屏障。此前，我们测量了来自两个种群的成年家麻雀角质层的皮肤水分流失（CWL）和脂质组成，一个种群生活在沙特阿拉伯的沙漠地区，另一个种群生活在气候温和的俄亥俄州。与生活在气候温和地区的麻雀相比，成年沙漠家麻雀的CWL较低，游离脂肪酸比例较低，角质层中神经酰胺和脑苷脂的比例较高。在本研究中，我们调查了在低湿度和高湿度环境中饲养的沙漠和气候温和地区的雏鸟角质层CWL和脂质组成的发育可塑性，并将我们的结果与之前关于成年鸟的研究进行了比较。我们测量了雏鸟的CWL，并使用薄层色谱法分析了角质层的脂质组成。我们发现，来自这两个地区的雏鸟在自然环境中的CWL都高于成年鸟，这是角质层脂质组成发生重大变化的结果。CWL可塑性的表达似乎是对不同生命阶段相反的选择压力（体温调节和水分保持）的一种反应，而CWL的调节在其中起着关键作用。与生活在气候温和地区的雏鸟相比，沙漠雏鸟在CWL和角质层脂质组成方面表现出更大程度的可塑性，这一发现与以下观点一致：暴露于更多环境压力下的生物体应该比生活在更良性环境中的个体具有更高的可塑性。
