CRUI: Osmoregulation in Euryhaline Fish: Physiology, Ecology and Molecular Biology.

大多数鱼类完全被限制在淡水（FW）或海水（SW）中，不能生活或适应其他环境。 可能令人惊讶的是，所有硬骨鱼血液中的内部盐和有机分子（溶质）都保持在“中间”浓度（实际上与哺乳动物相似）。 换句话说，盐水中的鱼可能会受到压力，因为它们生活在一个大约是血液三倍咸的介质中，因此必须“泵出”摄入的额外盐。 这需要分子转运蛋白（如钠/钾泵和其他离子泵和通道）。 另一方面，FW鱼面临着“浸水”的问题。 换句话说，组织和血液中较高浓度的盐会导致鱼通过扩散（也称为渗透）获得水分。 这些鱼必须排出多余的水分并保存盐分。 他们通过分子转运蛋白来实现这一点。 一般来说，内部盐和水平衡的控制（盐调节）需要大量的代谢能量来为其提供动力。 正如大多数人所知，少数鱼类，如鲑鱼和鳗鱼，一生中有一部分时间在FW，一部分时间在SW。 这些鱼从FW代谢到SW代谢，这是一个代谢压力很大的过程。 一种令人惊讶的小鱼（3英寸长），即鳉鱼（Fundulus heteroclitus），已被证明具有惊人的神经调节能力。 这种鱼可以无限期地生存在FW或SW高达3倍以上的浓度比海水。 此外，鳉鱼可能每天从西南部迁移到西南部，然后返回觅食（并在春季繁殖和产卵），这使得它们似乎异常擅长鱼类调节。 目前，人们对代谢机制，特别是参与其中的分子转运蛋白产生了浓厚的兴趣。 事实上，在鲑鱼和鳗鱼中也发现了许多在鳉鱼中发现的相同类型的蛋白质及其对盐度变化的反应。 然而，对于鳉鱼（也许还有其他鱼类），另一种处理盐度胁迫的机制被提出，称为行为调节。 这一假设的核心是，在其他条件相同的情况下，鳉鱼会试图游上FW流，直到其内部的盐和水的成分与外部水的成分相似（约1/3强度SW），并留在那里保存代谢能量，否则这些能量将被消耗在将盐泵入或泵出鱼中。 初步数据支持这一假设，即鳉鱼可能寻求盐度约1/3的SW。 这一新观点在生理学和生态学上具有广泛的意义。 主要研究人员将测量鳉鱼的代谢能量调节需求。 使用基于DNA的技术，他们将测量鳉鱼中分子转运蛋白的存在和变化。 他们还将调查野生鳉鱼的生态学，并试图将自然分布和繁殖行为与预期的盐度偏好相关联。 该项目的一个非常重要的部分是，主要研究人员将领导一个由8名本科生组成的团队，每年（4年），他们将在学年期间在他们的家乡机构进行这项研究，然后在夏季来到荒岛山生物实验室进行实地考察，生理学和分子生物学。 学生将有机会在该国最好的海洋实验室之一学习许多领域的现代技术的同时进行原创研究。 预计这一经验显示这些学生的激情和科学研究的成就感，将激励他们在未来的职业生涯。

Most fish are confined entirely to fresh water (FW) or seawater (SW) and cannot live in or adapt to the other environment. What may be surprising is that the internal salts and organic molecules (solutes) in the blood of all bony fishes are maintained in an "intermediate" concentration (which is actually similar to that in mammals). In other words, fish in salt water may suffer stress because they are living in a medium about 3 times as salty as their blood and therefore must "pump out" extra salt that is ingested. This requires molecular transport proteins (such as the sodium/potassium pump and other ion pumps and channels). FW fish, on the other hand, face the problem of becoming "waterlogged". In other words, the higher concentrations of salts in their tissues and blood cause the fish to gain water by diffusion (also called osmosis). These fish must rid themselves of the extra water and conserve salts. They do this by using molecular transport proteins. In general the control of internal salt and water balance (osmoregulation) requires significant metabolic energy to power it. As most people know, a small number of fish like salmon and eels spend a part of their life in FW and part of their life in SW. These fish literally switchover from the FW metabolism to the SW metabolism, a process that may be metabolically stressful. A surprising little fish (3 inches long), the killifish (Fundulus heteroclitus), has been shown to have phenomenal osmoregulatory abilities. This fish can survive indefinitely in FW or in SW up to 3 times more concentrated than ocean water. Furthermore, killifish may migrate daily from SW to FW and back to feed (and to breed and lay eggs in the Spring) making them appear to be unusually adept at osmoregulation. At present there is intense interest in the metabolic machinery and especially the molecular transport proteins that are involved. Indeed, many of the same types of proteins and their responses to salinity change that are found in killifish also are found in salmon and eels. However, with killifish (and perhaps other fish as well) another mechanism, to deal with salinity stress has been suggested, termed behavioral osmoregulation. The heart of this hypothesis is that, all other things being equal, killifish will try to swim up FW streams to the point where their internal salt and water composition resembles that of the external water (about 1/3 strength SW) and stay there conserving metabolic energy that would otherwise be expended pumping salts in or out of the fish. Preliminary data support the hypothesis that killifish may seek salinities about 1/3 that of SW. This new idea has broad implications physiologically and ecologically. The principal investigators will measure the metabolic energy requirements for osmoregulation in killifish. Using DNA based techniques, they will measure the presence of and changes in the molecular transport proteins in killifish. They also will investigate the ecology of wild killifish and attempt to correlate natural distributions and breeding behavior with projected salinity preferences. A very important part of this project is that the principal investigators will lead a team of 8 undergraduate students per year (for each of 4 years) who will work during their academic year on this research at their home institutions and then come to Mount Desert Island Biological Laboratory for 2 months during the summer to do fieldwork, physiology and molecular biology. The students will have the opportunity to do original research while learning modern techniques in many fields at one of the country's finest marine laboratories. It is expected that this experience show these students the passion and fulfillment of scientific research that will motivate them in their future careers.