Nitrogen excretion and acid-base regulation in invertebrate systems: Mechanisms, regulation and the specific role of Rh-proteins and AMTs.

氨是蛋白质代谢产生的高毒性废物。在吸氨动物（例如水生无脊椎动物和鱼类）中，氨直接排泄而不会转化为毒性较小的分子，如尿素或尿酸，有效的排泄系统对于将细胞和体液氨水平保持在可耐受范围内至关重要。虽然CA。98%（= 30门）的所有动物是无脊椎动物，我们的知识，氮排泄策略和机制，在这个优势群体是相当小的。拟议研究的目标是获得氨排泄途径和机制的第一个和详细的见解，在各种不同的无脊椎动物群体，包括环节动物（淡水水蛭），线虫（土壤生活蛔虫），软体动物（淡水贻贝），蛛形纲动物（海水马蹄蟹）和甲壳类动物（新鲜，半咸水和海水螃蟹）。本论文的主要研究内容包括三个方面：（1）水生无脊椎动物的实际排泄机制，以探索共同的祖先排泄策略;（2）系统发育的古细菌和植物的“AMTs”和土壤线虫中的远亲动物的“Rh-蛋白”的进化和功能，线虫是一种表达两种类型氨转运蛋白的过渡动物;（3）甲壳动物排氨与酸碱平衡的关系以及全球水环境pCO 2浓度升高和海洋酸化对广盐性蟹类pH调节的影响。这三个目标将提供新的见解的进化的氨排泄机制和酸碱调节的古无脊椎动物，包括Rh蛋白和AMTs作为NH3，CO2或H+通道的作用。预计将发现基本和一般的氮排泄和pH调节策略。了解氨排泄机制以及动物对环境氨水平升高的反应对于保护计划至关重要，这些计划旨在保护生活在受富含氨的农业径流威胁的水生栖息地的动物群落，并管理水产养殖设施。

Ammonia is a highly toxic waste product derived from protein metabolism. In ammoniotelic animals (e.g. aquatic invertebrates and fish), where ammonia is excreted directly and not transformed into less toxic molecules such as urea or uric acid, an effective excretion system is essential to keep cellular and body fluid ammonia levels within a tolerable range. Although ca. 98% (= 30 phyla) of all animals are invertebrates, our knowledge of nitrogen excretion strategies and mechanisms in this dominant group is rather diminutive. The goal of the proposed research is to gain first and detailed insights of ammonia excretion pathways and mechanisms in a wide variety of different invertebrate groups, including annelids (freshwater leeches), nematodes (soil living roundworms), mollusks (freshwater mussels), arachnids (seawater horseshoe crabs) and crustaceans (fresh-, brackish-, and seawater crabs). The proposed research consists of three main objectives, investigating: (1) the actual excretion mechanisms in aquatic invertebrates to explore common ancestral excretion strategies; (2) the evolution and function of the phylogenetic ancient bacterial and plant "AMTs" and the distantly related animal "Rh-proteins" in the soil nematode Caenorhabditis elegans, a transitional animal that expresses both types of ammonia transporters; (3) the relation of ammonia excretion and acid-base balance in crustaceans and the effects of predicted increases in global aquatic pCO2 levels and ocean acidification on the pH-regulation in euryhaline crabs. The three objectives will provide novel insights of the evolution of ammonia excretion mechanisms and acid-base regulation in phylogentic ancient invertebrates, including the roles of Rh-proteins and AMTs as NH3, CO2 or H+ -channels. It is expected that fundamental and general nitrogen excretion and pH regulatory strategies will be discovered. Understanding the ammonia excretion mechanisms as well as the animal's responses towards elevated environmental ammonia levels are crucial for conservation programs, which are intended to protect animal communities living in aquatic habitats threatened by ammonia-rich agricultural run-off and also to manage aquaculture facilities.