Evolution of Ureotely in Batrachoidid Fishes

9507239沃尔什动物如何排泄废氮的进化的大致轮廓是相当好的理解的。完全水生的动物通常会排泄氨作为它们的主要含氮废物，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，会排泄尿素和尿酸等含氮废物，这些废物毒性较小，可以在较高浓度下安全储存。然而，这些毒性较低的化合物的生产成本很高，因为它们的能量含量较高。尽管花费不菲，有一种鱼，海湾蟾鱼，最近被证明可以合成和排泄尿素。这项研究旨在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环境中提供的优势。初步结果表明，环境胁迫诱导鱼产生尿素。将在实验室和鱼类的自然环境中使用各种生化、生理、分子和现场技术，以确定尿素排泄的合成途径、控制机制和功能意义。这项研究将为脊椎动物一项重要生理特征的遗传机制、生理意义和进化提供独特的见解。最终，这可能会带来基因进步，使养殖产生尿素而不是氨的鱼类成为可能，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产生的触发因素，那么丰富的鱼类可能使其成为沿海水环境生物学上重要变化的有用生物分析方法。

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.