Integration of Water and Energy Balance in Hummingbirds

[9307024] Beuchat蜂鸟几乎完全以花蜜为食，当能量需求高时，它们每天消耗的液体是自身体重的三倍多。然而，与此同时，蜂鸟的高代谢需要从快速通过胃肠道的稀释食物来源中有效地提取营养物质和电解质，以有效地提取营养物质，保存电解质，并快速消除水分。对于蜂鸟来说，同时平衡能量、水和离子通量是一项重大挑战，它提出了关于蜂鸟形态学和生理学的基本问题。本研究提出解决一个核心问题：蜂鸟的肾脏和胃肠道以何种方式和机制促进水和离子稳态，同时允许最大效率的能量获取？利用人造花蜜中的同位素标记物，我可以确定肠道吸收的摄入液体的比例以及肾脏在不消耗体内电解质的情况下排出多余水分的能力。能量和营养物质提取的效率是在影响蜂鸟能量需求、电解质平衡和饮食质量的条件下确定的。总之，这些研究将提供有关蜂鸟独特的适应性的信息，这些适应性使蜂鸟专门以液体食物为食。＊＊＊

9307024 Beuchat Hummingbirds subsist almost entirely on a liquid diet composed of floral nectar, and when energy demands are high they can consume more than three times their own body mass in fluid per day. At the same time, however, the hummingbird's high metabolism requires efficient extraction of nutrients and electrolytes from a dilute food source that is passing rapidly through the gastrointestinal tract for efficient nutrient extraction, electrolyte conservation, and rapid elimination of water. For a hummingbird to simultaneously balance energy, water, and ion fluxes is a major challenge that raises fundamental questions about hummingbird morphology and physiology. This study proposes to address a central problem: In what ways and by what mechanisms do the kidney and gastrointestinal tract of hummingbird contribute to water and ion homeostasis while at the same time allowing maximum efficiency of energy acquisition? Using isotopically-labeled markers in artificial nectar, I can determine the fraction of ingested fluid that is absorbed by the intestine and the capacity of the kidney to eliminate excess water without depleting the body of electrolytes. The efficiency of energy and nutrient extraction are determined under conditions that influence the hummingbird's energy requirements, its electrolyte balance, and the quality of its diet. Together, these studies will provide information about the unique adaptations that allow hummingbirds to specialize on a liquid diet. ***