Physiological Adaptions for a Deadly Diet: Bioaccumulation Mechanisms of Defensive Chemicals in a Poison Frog

南美毒蛙颜色鲜艳，毒性很大，这表明它们对潜在的捕食者来说是不好吃的。毒蛙本身并不产生这些毒素，而是从它们吃的蚂蚁和螨虫中获取毒素。虽然科学家们早就知道毒蛙会从它们的饮食中积累毒素，但它们是如何积累有毒化学物质的还不清楚。这项研究的目的是了解毒蛙是如何积累毒素并将毒素从肠道通过肝脏转移到皮肤储存的。描述这一过程将增加我们对动物如何进化出特殊生理机制以从环境中获取新资源的认识。由于这些毒素和其他蛙类化学物质中的许多都是与许多药物相似的小分子，了解毒蛙如何运输这些化学物质可能会让我们对这一过程与其他动物（包括哺乳动物）有何不同有更全面的了解，因为其他动物不能积累这些化合物。这项研究将为美国和厄瓜多尔的所有年龄组提供学习经验，厄瓜多尔将对毒蛙进行实地调查。该奖项由美国国家科学基金会国际科学与工程办公室共同资助。研究将通过“小青蛙学校计划”（Little Froggers School Program）纳入K-12科学课堂，该计划向孩子们传授生态学和进化知识。高中生物教师将参与厄瓜多尔的实地考察，并将他们的研究成果纳入他们的科学课程。这项研究还将涉及培养化学、生态学、蛋白质组学和生物信息学方面的本科生、研究生和博士后。毒蛙从节肢动物获得化学防御，并进化出专门的生理适应毒素的生物积累和修饰。尽管隔离防御性化学物质是节肢动物猎物和青蛙捕食者之间生态和进化关系的一个组成部分，但毒蛙用来隔离和修饰毒素的机制在很大程度上是未知的。本研究的总体目标是通过以下三个方面来了解毒素在毒蛙体内生物积累的生理机制：1)利用热蛋白质组学分析确定与小魔蛙饮食毒素生物积累有关的蛋白质。2)采用圈养饲养实验和液相色谱质谱法测定不同遗传背景下小魔蛙的毒素药代动力学。3)利用串联液相色谱-质谱法分析不同小魔鬼蛙种群毒素结合蛋白丰度的差异，验证不同小魔鬼蛙种群对有效积累当地节肢动物猎物中发现的化学物质具有局部适应性的假设。总之，这项工作将测试毒素结合蛋白水平的变化是由于种群之间的遗传差异，对饮食毒素可用性的反应，还是遗传和环境共同作用。这项研究将更广泛地增加生态资源如何塑造动物生理学的知识。

South American poison frogs are brightly colored and highly toxic, advertising their unpalatabilily to potential predators. Poison frogs do not make these toxins themselves, but instead acquire toxins from the ants and mites they consume in their diet. Although scientists have long known that poison frogs accumulate toxins from their diet, how the frogs accumulate the toxic chemicals is unknown. The goal of this research is to understand how poison frogs accumulate and move toxins from the gut through the liver and to the skin for storage. Describing this process will increase our knowledge of how animals have evolved special physiological mechanisms to acquire new resources from their environment. As many of these toxins and other frog chemicals are small molecules similar to many pharmaceutical drugs, understanding how poison frogs transport these chemicals may yield more general insights about how this process is different from other animals (including mammals), which cannot accumulate these compounds. This research will provide learning experiences to all age groups in both the United States and in Ecuador, where fieldwork on poison frogs will be conducted. This award is co-funded by the NSF Office of International Science and Engineering. Research will be incorporated into science K-12 classrooms through the Little Froggers School Program, which teaches children about ecology and evolution. High school biology teachers will be involved in fieldwork in Ecuador and will incorporate their research findings into their science curriculum. This research will also involve training of undergraduate, graduate, and postdoctoral students in chemistry, ecology, proteomics, and bioinformatics.Poison frogs acquire chemical defenses from dietary arthropods and have evolved specialized physiological adaptations for toxin bioaccumulation and modification. Although sequestering defensive chemicals is one component of well-studied ecological and evolutionary relationships between arthropod prey and frog predators, the mechanisms used by poison frogs to sequester and modify toxins are largely unknown. The overall goal of this research is to understand the physiological mechanisms of toxin bioaccumulation in poison frogs through three aims: 1) Identify proteins involved in bioaccumulation of dietary toxins in the Little Devil frog using thermal proteome profiling. 2) Determine toxin pharmacokinetics in distinct genetic backgrounds of the Little Devil frog using captive feeding experiments and liquid chromatography mass spectrometry across several time points. 3) Test the hypothesis that different Little Devil frog populations have local adaptations to efficiently accumulate chemicals found in local arthropod prey by characterizing population differences in toxin-binding protein abundance using tandem liquid chromatography mass spectrometry. Together, this work will test whether variation in toxin-binding protein levels is due to genetic differences between populations, response to dietary toxin availability, or a combination of both genetic and environmental contributions. This research will more broadly add to the knowledge of how ecological resources shape animal physiology.