CAREER: Colonizing Land Via the Estuarine Route: Ontogeny of Osmoregulation and Settlement Behaviors in Three Brackish Water Fiddler Crabs

职业：通过河口途径殖民陆地：三种半咸水招潮蟹的渗透调节和定居行为的个体发生南卡罗莱纳大学陆地殖民是动物生命史上最重要的进化事件之一。虽然脊椎动物是陆地动物群中引人注目的成员，但数量最多、种类最多的陆地动物实际上是由海洋祖先进化而来的无脊椎动物。殖民海洋无脊椎动物面临的第一个挑战是需要改变幼虫阶段，以便它们在成年陆地栖息地附近招募。幼虫的定居行为必须改变，幼虫必须进化出能够忍受它们在陆地上遇到的生理压力的能力。在完全陆生的动物中，这些生命的早期阶段是在陆地上的保护卵膜内或在成年父母体内发育的。这项研究将检查Uca minax的幼虫行为和生理变化，Uca minax是一种淡水招潮蟹，处于陆地入侵的中间阶段。为了检验这些变化，我们将把最小美洲狮与两种陆地上的近亲——美洲虎和美洲虎进行比较。这三种物种都在沿海海水中进行幼虫发育。利用分子遗传技术，这些招潮蟹物种将被追踪，从它们离开开阔的沿海水域，进入南卡罗来纳州北部的入口河口，直到它们作为幼崽加入成年种群。这将解开幼蟹是直接在成年蟹的栖息地定居，还是随着它们的发育和生长逐渐迁移，还是在河口随机定居，在不适合它们的地区死亡的谜团。一旦确定了沉降模式，幼虫对不同盐度环境下成虫气味线索的反应将在实验室进行研究。与其他两种物种相比，最小的一套不同的行为反应可能有助于解释它是如何入侵淡水和陆地栖息地的。为了确定最小螯虾幼体是否在生理上适应低盐度条件，将在一系列盐度（海洋强度到淡水强度）中对最小螯虾幼体和幼体的存活率与美洲螯虾、美洲螯虾和乌拉圭螯虾（一种来自巴西的远亲物种）的存活率进行比较。还将评估这些盐度下的渗透调节能力（控制内部盐浓度的能力）。这样，就有可能探索招潮蟹在入侵土地的过程中渗透调节变化的演变。除了产生进化见解外，这项研究还将对生态和教育产生影响。招潮蟹是东南河口的主要生物，它们是鸟类和鱼类的重要猎物，并改变了它们挖洞和觅食地区的景观地形和物种组成。更详细地了解招潮蟹的扩散模式、行为和生理将有助于对河口的监测。这项工作的教育效益将来自于加强有色人种在生物学研究中的参与水平。为此，将从南卡罗来纳大学和附近的传统黑人学院和大学招募有色人种的研究生和本科生来协助拟议的研究。此外，本科生和研究生将把科学工作的各个方面转化为K-12学生的实践活动，这些活动将在当地小学生的帮助下开发一个关于海洋和陆地无脊椎动物的网站。

CAREER: Colonizing land via the estuarine route: ontogeny of osmoregulation and settlement behaviors in three brackish water fiddler crabsRenae J. BrodieUniversity of South CarolinaThe colonization of land is one of the most significant evolutionary events in the history of animal life. While vertebrates are conspicuous members of terrestrial faunas, the most prolific and diverse land animals are actually invertebrates that have evolved from marine ancestors. One of the first challenges faced by colonizing marine invertebrates is the need to modify larval stages so they recruit near adult terrestrial habitats. Larval settlement behaviors must change and larvae must evolve the capability to tolerate physiological stresses that they encounter on land. In completely terrestrial animals, these early life stages develop on land within protective egg membranes or inside the adult parent. This study will examine changes in larval behavior and physiology in Uca minax, a freshwater fiddler crab that is at an intermediate stage of land invasion.To examine these changes, U. minax will be compared to two less terrestrial relatives, Uca pugilator and Uca pugnax. All three species undergo larval development in coastal marine waters. Using molecular genetic techniques, these fiddler crab species will be tracked from when they leave open coastal waters and enter South Carolina's north inlet estuary, until they join adult populations as juveniles. This will resolve the mystery of whether young crabs settle directly into adult habitats, move in gradually as they develop and grow, or settle randomly throughout the estuary, dying out in areas that are not suitable for them. Once patterns of settlement are established, larval responses to adult odor cues in different salinity environments will be investigated in the lab. A different suite of behavioral responses by U. minax compared to the other two species may help to explain how it invades adult freshwater and terrestrial habitats.To determine if young U. minax are physiologically adapted to survive low-salinity conditions, survivorship of larval and juvenile U. minax in a series of salinities (ocean-strength to freshwater) will be compared to that of U. pugilator, U. pugnax and U. uruguayensis, a distantly-related species from Brazil. Osmoregulatory ability (ability to control internal salt concentrations) at these salinities will also be assessed. In this way, it will be possible to explore the evolution of osmoregulatory changes in development that accompany the invasion of land in fiddler crabs.In addition to yielding evolutionary insights, this study will have ecological and educational impacts. Fiddler crabs are dominant players in southeastern estuaries, where they are important prey for birds and fishes, and modify landscape topography and species composition in areas where they burrow and feed. A more detailed understanding of the dispersal patterns, behavior and physiology of young fiddler crabs will facilitate the monitoring of estuaries. The educational benefits of this work will come from a strong effort to increase the level of participation of people of color in biological research. To this end, graduate and undergraduate students of color will be recruited from the University of South Carolina and nearby Historically Black Colleges and Universities to assist in the proposed research. Also, undergraduate and graduate students will turn aspects of the scientific work into hands-on activities for K-12 students that will be developed for a Web site about marine and terrestrial invertebrates with the assistance of local elementary-school children.