Skin Lipids and Cutaneous Water Loss Among Larks Along an Aridity Gradient

提案标题：沿着干旱梯度的云雀皮肤脂质和皮肤水分流失。主要研究者：约瑟夫B博士。威廉姆斯，系进化，生态学和有机生物学，俄亥俄州州立大学，哥伦布，OH 43210。在这一转变过程中，动物进化出了减少水分流失的皮肤。随着后来发展的能力，保持高体温，称为吸热，水分流失的问题加剧，因为高代谢率与增加的水分损失从呼吸道和排泄。由于能量消耗和水分损失的高速率，吸热动物不适合生活在沙漠，高环境温度，低降雨量和低植物生长的地区。然而，尽管如此，鸟类占据了世界上最干燥的沙漠。最近的研究表明，干旱适应的云雀有一个减少的总蒸发水分损失，呼吸水分损失和通过皮肤的水分损失的总和，与同一家庭内的mesic亲属。沙漠鸟类可以通过减少皮肤的水分流失来减少总的蒸发水分流失。研究表明，脊椎动物中阻止水蒸气扩散的屏障位于表皮的无生命外层。该提案概述了一项综合研究，旨在促进我们对环境，皮肤水分流失，皮肤结构，表皮外层脂质成分之间相互作用的理解，以及皮肤水分流失增加对自然环境中行为和/或生存的影响。比较方法和控制实验改变温度，空气中的水蒸气含量，和水合状态将被用来检查鸟类皮肤适应沙漠条件和可逆的表型可塑性对水分通过皮肤损失的作用。生理表型的变异也可能是由于发育过程中环境的差异造成的。计划的实验，阐明如何在发展过程中的空气中的水含量的变化影响皮肤水分流失的成年人。描述种群内短期和进化变化的潜力，对于预测由于全球变暖导致地球温度上升而导致的分布变化和灭绝概率至关重要。

Title of Proposal: Skin lipids and cutaneous water loss among larks along an aridity gradient.Principal Investigator: Dr. Joseph B. Williams, Dept Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, OH 43210.A major evolutionary event that shaped current vertebrate life was the transition from water to land. During this transition, animals evolved skin that reduced water loss. With the later development of the ability of maintain high body temperature, called endothermy, problems of water loss were exacerbated because high metabolic rates are associated with increased water losses from respiratory passages and by excretion. With high rates of energy expenditure and water loss, endotherms make poor candidates for living in deserts, regions of high ambient temperature, low rainfall, and low plant growth. Yet despite this, birds occupy the driest deserts in the world. Recent work has indicated that arid-adapted larks have a reduced total evaporative water loss, the sum of respiratory water loss and water loss through the skin, compared with mesic relatives within the same family. Desert birds could reduce their total evaporative water loss by decreasing their water loss through their skin. Research suggests that the barrier to water vapor diffusion in vertebrates resides in the non-living outer layer of the epidermis. This proposal outlines an integrated study designed to advance our understanding of the interplay between environment, water loss through the skin, skin structure, lipid composition of the outer layer of the epidermis, and the effect that increased cutaneous water loss has on behavior and/or survival in a natural setting. The comparative method and controlled experiments varying temperature, water vapor content of the air, and hydration state will be used to examine adaptation of the avian skin to desert conditions and the role of reversible phenotypic plasticity on water loss through the skin. Variation in physiological phenotype may also result from differences in environment during development. Experiments are planned that shed light on how variation in the water content of the air during development influences cutaneous water loss in adults. Characterization of the potential for both short-term and evolutionary change within populations will be of crucial importance in predicting changes in distribution and the probability of extinction with the rise in temperature of the earth as a result of global warming.