Regulation of Ureotely in Batrachoidid Fishes

蝠鲼科鱼类中尿素的调控

• 批准号: 0090355
• 负责人: Patrick Walsh
• 金额: $ 36.96万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-01 至 2005-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0090355&HistoricalAwards=false
• 关键词: Regulation; Ureotely; Batrachoidid; Fishes

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.

直到最近，人们普遍认为鱼类和其他水生物种将氨作为餐后废物排出。氨最终是有毒的，主要是对大脑有毒，因此鱼类和其他水生物种一旦产生氨，就会立即将其排出体内，其有害影响会立即被周围水的“无限”水槽稀释。然而，当动物进化到在陆地上生活，并且不受周围水环境的稀释作用时，它们需要采取替代方法来清除体内的这种毒素。因此，陆生动物会排泄替代废物（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，而不会产生有害影响，直到它们能够消耗足够的水来排泄它们。然而，近年来，PI 发现美国东南部的一种常见鱼类——海湾蟾蜍 (Opsanus beta) 却是这一规则的例外，它在某些应激环境下会排泄尿素而不是氨。因此，该研究项目的目标是了解这种鱼类如何能够制造和排泄尿素，并了解其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，因此可以合理地假设制造和排泄尿素的能力具有选择性优势，并有助于鱼类的生存和繁殖能力。研究人员将采取三种方法来了解鱼类排泄尿素的机制和意义。该研究的一部分将采用生化和分子生物学技术来了解鱼如何从制造氨转变为制造尿素，重点关注肝脏的酶。 该研究的第二部分将集中于尿素如何在鳃中排出的生理学研究。该研究的第三部分将集中于现场实验，测试以下假设：尿素生产对鱼类的生存很重要，因为鱼类生活在氨浓度高的环境中，和/或尿素排泄有助于鱼类更好地通过化学手段伪装自己以躲避捕食者。这项研究将阐明水生生物在个体和进化时间尺度上能够以多快的速度适应不断变化的环境。随着我们的环境因人类的影响而发生变化，此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，因此这些研究的结果可能对鱼类生产产生影响。