Moving From Sea to Land Via the Freshwater Route: Larval Physiology and Mode of Recruitment in a Freshwater Fiddler Crab

在这项研究中，我们将开发一种分子方法来鉴定美国东南部盐沼群落中常见的三种招潮蟹的隐幼虫形式。在盐沼无脊椎动物中，研究最多的是这些近亲的成年蟹，如小蟹、舌蟹和角蟹，但对蟹的幼虫和幼蟹的研究一直受到阻碍，因为它们在生命早期的形态上难以区分。使用快速，廉价的分子分析，我们将绘制这三个物种的分布图，从春末开始，当它们在开放的沿海水域完成幼虫发育后，开始进入南卡罗来纳的北入口河口，直到深秋，当一年中的最后一个年轻人加入成熟的成年种群。根据这些信息，我们将制作一个高分辨率的Uca蟹每年入侵沼泽的模型。我们将确定三个物种的幼体进入它们的成年同伴优先占据的栖息地的时间、位置和程度。我们将了解这三种物种的迁徙是否不同，或者它们的幼鸟是否均匀地渗透到所有地区，以及定居后死亡率的差异决定了成虫在河口内的分布。实地的估计将通过实验室实验加以完善，在实验室实验中，这三种螃蟹的幼蟹将在低或高盐度条件下暴露于成年栖息地的沉积物中。小蟹对这些环境线索的反应可能解释了它们定位成年蟹栖息地的能力。这项研究的更广泛的影响在于我们正在开发的分子分析，以区分这三种螃蟹的幼体。招潮蟹通过改变物种组成、景观地形和它们挖洞和觅食地区的水化学，严重影响了东南河口。此外，成年螃蟹是湿地鸟类的主要食物，而螃蟹的幼虫则是小型鱼类的重要猎物，而大型鱼类则是商业和运动渔业的猎物。我们的分析将使我们能够评估沼泽生态系统随时间的稳定性，并将有助于估计甲壳类生物多样性。这项试验的发展将使我们能够第一次详细研究这些被广泛研究的螃蟹的整个生命周期，从而消除我们对盐沼中出生、招募和死亡的理解上的一个巨大障碍。

In this study, we will develop a molecular method to identify the cryptic larval forms of three fiddler crab species common in salt marsh communities of the southeastern United States. While the adults of these closely related species, Uca minax, Uca pugnax, and Uca pugilator, are among the most studied of salt marsh invertebrates, work on larval and juvenile crabs has been hindered because they are morphologically indistinguishable at these early life stages. Using a fast, inexpensive molecular assay, we will map the distribution of these three species starting in late spring when they begin to enter the mouth of South Carolina's North Inlet estuary after completing larval development in open coastal waters until late fall when the last of the year's young have joined the established adult populations. From this information, we will produce a high-resolution model of the annual invasion of the marsh by Uca crabs. We will determine the timing, position, and degree of penetration by young of the three species into habitats preferentially occupied by their adult counterparts. We will learn if the three species migrate differently, or if their young penetrate all areas equally and differential mortality after settlement determines adult distributions within the estuary. Estimates from the field will be refined with lab-based experiments in which young crabs of the three species will be exposed to sediment from adult habitats under low or high salinity conditions. How young crabs respond to these environmental cues may explain their ability to locate adult habitats.The broader impact of this study lies in the molecular assay that we are developing to differentiate young of these three crab species. Fiddler crabs heavily impact southeastern estuaries by modifying species composition, landscape topography, and water chemistry in areas where they burrow and feed. Also, adult crabs can comprise a large portion of the diets of wetland birds and crab larvae are important prey for small fishes that are eaten by larger fishes exploited by commercial and sport fisheries. Our assay will allow us to assess the stability of marsh ecosystems over time and will be useful in estimating crustacean biodiversity. The development of this assay will eliminate a large hurdle in our understanding of birth, recruitment, and death in the salt marsh by allowing us to investigate the full life cycles of these widely studied crabs in detail for the first time.