Evolution of Ureotely in Batrachoidid Fishes

9507239沃尔什动物排泄废氮的进化大致轮廓已相当清楚。全水生动物通常排泄氨作为其主要含氮废物，因为它们周围的水会稀释有毒的氨。陆生和半陆生动物为了节约用水，排泄含氮废物，如尿素和尿酸，这些废物毒性较小，可以在较高浓度下安全储存。然而，这些毒性较小的化合物的生产成本很高，因为它们的能量含量较高。尽管付出了这样的代价，一种鱼，海湾蟾蜍鱼，最近被证明可以合成和排泄尿素。这项研究的目的是了解鱼用来制造尿素的生化途径，它们与陆地生物的相似性，以及这种能力的遗传基础。实地研究将确定这种能力在水生环境中有什么优势。初步结果表明，环境胁迫诱导鱼产生尿素。将在实验室和鱼的自然环境中使用各种生化、生理、分子和现场技术来确定尿素排泄的合成途径、控制机制和功能意义。本研究将对脊椎动物这一重要生理性状的遗传机制、生理意义及其进化提供独特的见解。最终，它可能会导致遗传上的进步，使养殖的鱼能够产生尿素而不是氨，从而通过减少控制氨水平的需要来简化高密度水产养殖。如果环境压力是启动尿素生产的触发因素，那么鱼的丰度可能使其成为沿海水环境中生物重要变化的有用生物测定。

9507239 Walsh The broad outlines of the evolution of how animals excrete their waste nitrogen are reasonably well understood. Fully aquatic animals typically excrete ammonia as their main nitrogenous waste product because the water surrounding them will dilute the toxic ammonia. Terrestrial and semi- terrestrial animals, in order to conserve water, excrete nitrogenous waste products like as urea and uric acid that are less toxic and can be stored safely at higher concentrations. The production of these less toxic compounds is costly, however, because of their higher energy content. In spite of this expense, one fish, the gulf toadfish, has recently been shown to synthesize and excrete urea. This research is aimed at understanding the biochemical pathways the fish uses to make urea, their similarity to those of terrestrial organisms, and the genetic basis for this ability. Field studies will determine what advantage this ability provides in an aquatic environment. Preliminary results indicate that environmental stress induces the fish to make urea. A variety of biochemical, physiological, molecular and field techniques will be used both in the laboratory and in the fish's natural setting to identify synthetic pathways, control mechanisms, and the functional significance of urea excretion. This research should provide unique insight into the genetic mechanisms, physiological significance and evolution of an important physiological trait in vertebrate animals. Ultimately, it may lead to genetic advances that would enable culture of fish that make urea instead of ammonia that could simplify high-density aquaculture by reducing the need to control ammonia levels. If environmental stress is the trigger that initiates urea production, the abundance of the fish may make it a useful bioassay for biologically im portant changes in coastal water environments.