Developing a Comprehensive Blood Volume Budget for Amphibians

点击翻译按钮获取中文摘要

9603025 Hillman Amphibians lose water very quickly, which must be replenished to sustain life. As terrestrial vertebrates they consequently lose and gain water at ten times the rate of other vertebrates. There is a greater potential for water deficits to occur (water loss exceeds water gain) as a consequence of these high water turnover rates. Natural selection has favored tolerance to periodic water deficits, its in amphibians, with more terrestrial species having greater dehydration tolerance than aquatic species. Amphibians have a two to four fold greater dehydration tolerance than mammals. They consequently represent an excellent vertebrate model system to unravel what cardiovascular mechanisms are important in dehydration tolerance. The cardiovascular system must deal with a decrease in its volume during dehydration. The amphibians ability to compensate for low blood volume is different between different species and remarkable in comparison to other vertebrates. The first step in describing the mechanisms involved in compensating for a decrease in blood volume is to develop a budget for all the avenues of fluid entry and fluid loss in the amphibian circulatory system. The PI plans to develop such a blood volume budget for two species which differ in their tolerance to dehydration and ability to maintain blood volume. This entails quantifying the volume of fluid moving through the kidneys, skin, bladder, lymph, nephrostomes and leaks in the capillaries. The PI will describe the range of flows possible in low volume and high volume conditions across the various pathways of exchange. The PI will also investigate some aspects of the neuroendocrine control of these pathways of fluid movement. The work will: 1 ) provide the first non-mammalian blood volume budget; 2) provide the first measurements of vascular leakiness and compliance for amphibians; 3) provide a test of which aspects of the budget correlate with dehydration tolerance; and 4) increase understanding of what c ardiovascular adaptations were important in the aquatic to terrestrial transition in vertebrate evolution. ***