RUI: Collaborative Research: The impact of symbiont-larval interactions on species distributions across southwestern Pacific hydrothermal vents

与微生物共生是普遍存在的，对发育和营养等基本生物学功能至关重要。因此，宿主动物的成功可能取决于它找到并与其微生物伙伴(S)交往的能力。虽然一些宿主为了保证这一点直接将它们的共生体从父母传给后代，但从环境中获得微生物共生体对许多必须共生的动物的生存至关重要。了解自由生活的共生体种群以及宿主是如何获得这些共生体的，对于我们理解所有生态系统中的生态过程是至关重要的，但对这两者几乎一无所知。热液喷口生态系统为研究微生物共生体在宿主、群落和生态系统水平上的作用提供了重要机会，因为这些生态系统主要由动物主导，这些动物的生存显然与获得一个或几个特定的共生体有关。这个项目开始填补我们对驱动热液喷口群落结构的因素的理解的空白，解决自由生活的共生体种群影响宿主动物建立的可能性，同时也扩大了我们关于宿主相关微生物对适用于整个生态系统的基本生态过程的影响的一般知识。该项目的成果将通过教育视频和现场直播分享给史密森学会的国家自然历史博物馆和大学运营的博物馆。研究人员还将设计和实施一项适合初中和高中课堂的关于共生和热液喷口生物学的教育计划。最后，研究人员将在科学教育项目的研究和开发方面培训一批不同的本科生和研究生。该项目将专注于两个姐妹属的蜗牛，Alvinconcha和Ifremeria，这两个属主要分布在西南太平洋的喷口。在刘盆地(汤加)的喷口，三种Alviniccha和一种Ifremeria共存。这四个物种都在成年后的鳃组织中拥有不同的化学自养蛋白细菌谱系，这些细菌提供了它们的大部分营养。以前在该地区的工作表明，钉螺物种的结构分布与共生体化学自养代谢的关键化学底物的浓度相对应，这表明钉螺物种正在根据共生体的生理学分类到地球化学生境。目前尚不清楚这种分类是否发生在已建立的蜗牛-细菌共生环境中，也不清楚环境对特定共生体可用性的影响是否正在影响宿主物种的招募，因为到达和发育的蜗牛幼虫必须从环境中获得共生体。本研究的目的是1)通过采集幼螺、幼螺和成螺来评估共生排气螺的幼虫供应和种群结构；2)通过显微镜观察和对配子、幼虫和幼螺进行标记基因测序来研究共生体的发育时机；3)利用元基因组测序来定量环境中自由生活的共生体对到达的幼虫的可用性。总之，这一系列相互关联的努力将有助于更好地了解自由生活的细菌共生体种群、共生体获取的时机、宿主蜗牛的生活史，以及这些事物如何相互作用来塑造喷口群落。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Symbiosis with microbes is ubiquitous and critical to fundamental biological functions such as development and nutrition. Thus, the success of a host animal may depend on its ability to find and associate with its microbial partner(s). While some hosts directly transmit their symbionts from parent to offspring in order to guarantee this, acquisition of microbial symbionts from the environment is vital for the survival of many obligately-symbiotic animals. An understanding of the free-living symbiont population and how the host acquires those symbionts is fundamental to our comprehension of ecological processes in all ecosystems, yet almost nothing is known about either. Hydrothermal vent ecosystems provide important opportunities to investigate the role of microbial symbionts in host-, community-, and ecosystem-level ecology, since these ecosystems are dominated by animals whose survival is clearly linked to the acquisition of one or a few specific symbionts. This project begins to fill a gap in our understanding of the factors driving community structure at hydrothermal vents by addressing the potential for free-living symbiont populations to affect host animal establishment, while also expanding our general knowledge regarding the impact of host-associated microbes on fundamental ecological processes that apply across ecosystems. The results of this project will be shared via educational videos and live-broadcasts to the Smithsonian Institution's National Museum of Natural History and University-run museums. The investigators will also design and implement an educational program about symbiosis and hydrothermal vent biology suitable for middle and high school classes. Finally, the investigators will train a diverse group of undergraduate and graduate students in both research and the development of science educational programs. This project will focus on two sister genera of snails, Alviniconcha and Ifremeria, which predominate at vents in the southwestern Pacific. At vents in the Lau Basin (Tonga), three species of Alviniconcha and one species of Ifremeria coexist. These four species all host distinct lineages of chemoautotrophic proteobacteria in their gill tissue as adults that provide the bulk of their nutrition. Previous work in this region showed a structured snail species distribution that corresponds to the concentrations of key chemical substrates for symbiont chemoautotrophic metabolism, suggesting that snail species are sorting into geochemical habitats based on symbiont physiology. It is not clear if this sorting is occurring among established snail-bacteria symbioses, or whether environmental effects on the availability of specific symbionts are influencing the recruitment of host species, since arriving and developing snail larvae must obtain their symbionts from the environment. This study aims to 1) assess the larval supply and population structure of symbiotic vent snails via collections of larval, juvenile, and adult snails, 2) investigate the developmental timing of symbiont acquisition through microscopy and marker gene sequencing of gametes, larvae, and juveniles, and 3) use metagenomic sequencing to quantify the availability of free-living symbionts in the environment to arriving larvae. Altogether, this series of interlinked efforts will allow for an improved understanding of free-living bacterial symbiont populations, the timing of symbiont acquisition, and host snail life history, as well as how these things interact to shape vent communities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.