Regulation of Ureotely in Batrachoidid Fishes

直到最近，人们普遍认为鱼类和其他水生物种在进食后会将氨作为废物排出体外。氨最终是有毒的，主要是对大脑有害，所以鱼类和其他水生物种在氨产生后立即将其排出体内，其有害影响立即被周围“无限”的水所稀释。然而，当动物进化到生活在陆地上，并且没有周围水环境的稀释作用时，它们需要采用其他方法来清除体内的这种毒素。因此，陆生动物排泄替代废物（尿素和尿酸），它们可以将这些废物以更高的浓度储存在体内，直到它们能够消耗足够的水来排泄它们，才会产生有害影响。然而，近年来，pi发现美国东南部的一种常见鱼类，海湾蟾蜍鱼（Opsanus beta）是这个规则的一个例外，在某些压力环境下排泄尿素而不是氨。因此，这个研究项目的目标是了解这种鱼类是如何产生和排泄尿素的，并了解它这样做的生态和进化原因。制造尿素和尿酸的能力需要大量的能量，否则这些能量将用于躲避捕食者、繁殖等，因此有理由认为，制造和排泄尿素的能力具有选择性优势，有助于鱼的生存和繁殖能力。研究人员将采取三种方法来了解鱼体内尿素排泄的机制和意义。研究的一部分将采用生物化学和分子生物学技术来了解鱼是如何从制造氨转变为制造尿素的，重点是肝脏的酶。研究的第二部分将集中在尿素如何在鳃排泄的生理研究上。研究的第三部分将集中在实地实验上，以验证以下假设：尿素的产生对鱼类的生存很重要，因为鱼类生活在高氨浓度的环境中，或者尿素的排泄有助于鱼类更好地进行化学伪装，以躲避捕食者。这项研究将阐明水生生物在个体和进化时间尺度上适应不断变化的环境的速度有多快。由于人类的影响，我们的环境发生了变化，这类信息变得越来越有价值。此外，由于氨是水产养殖中必须去除的最重要的副产品之一，这些研究的结果可能对鱼类生产产生影响。

Until recently, it has commonly been accepted knowledge that fish and other aquatic species excrete ammonia as the waste product following a meal. Ammonia is ultimately toxic, primarily to the brain, so fish and other aquatic species rid their bodies of ammonia as soon as it is produced, and its harmful effects are immediately diluted by the "infinite" sink of the surrounding water. However, when animals evolved to live on land, and did not have the diluting effects of a surrounding water environment, they needed to adopt alternate means of ridding their bodies of this toxin. So, terrestrial animals excrete alternative waste products (urea and uric acid) which they can store in their bodies at higher concentrations without harmful effect until they are able to consume enough water with which to excrete them. However, in recent years, the PIs have discovered that a common fish in the Southeastern US, the gulf toadfish (Opsanus beta) is an exception to this rule, excreting urea instead of ammonia under certain stressful circumstances. Thus the goals of this research project are to understand how this fish species is able to make and excrete urea, and to understand the ecological and evolutionary reasons for why it does so. The ability to make urea and uric acid requires a great deal of energy, which would otherwise be spent on predator avoidance, reproduction, etc., so it is reasonable to assume that the ability to make and excrete urea is selectively advantageous, and contributes to the fish's ability to survive and propagate.The investigators will take three approaches to understanding the mechanisms and significance of urea excretion in fish. One portion of the study will employ biochemical and molecular biology techniques to understand how the fish shifts from making ammonia to making urea, focusing on enzymes of the liver. A second part of the study will focus on physiological studies of how urea is excreted at the gill. A third part of the study, will focus on field experiments that test the hypotheses that urea production is important to the survival of the fish because the fish lives in an environment with high ammonia concentration, and/or that urea excretion helps the fish to be better at chemically camouflaging itself from predators. This research will elucidate how rapidly aquatic organisms are able to adapt to changing environments on both an individual and an evolutionary time scale. This type of information becomes more and more valuable as our environment changes due to man's influence. Furthermore, since ammonia is one of the most important byproducts in aquaculture that must be removed, results of these studies may have implications for fish production.