Chemosymbiotic specificity and plasticity in thyasirid bivalves

在有机物高度富集的海洋沉积物中（例如纸浆和造纸厂或污水排放口附近、水产养殖圈、农业场地以及天然气和油田），微生物降解有机物，产生有毒的还原硫;有机物富集被认为是全世界沿海环境面临的最大问题之一。一个特殊的小，鲜为人知的蛤类（双壳类家庭Thyasiridae）往往是第一个和最丰富的殖民者丰富的环境，包括在几个网站沿着加拿大海岸线。 这些thyasirid蛤蜊能够在生活在鳃中的共生硫氧化细菌的帮助下在丰富的环境中茁壮成长;细菌共生体是蛤蜊的额外食物来源。 与其他来自深海热液喷口、冷泉或鲸鱼福尔斯的具有类似共生关系的动物不同，囊虫并不将细菌共生体保持在鳃细胞内，而是保持在鳃细胞外（细胞外）。 我的研究使用尖端的观察技术来研究thyasirid蛤的细胞外共生的特殊性，以及它如何影响它们从协会中获得的营养输入。 此外，我专注于不同地点之间的共生体丰度的变化，我使用的实验中，营养输入主机和共生体的操纵，以确定对蛤的影响。 最后，我研究的身份的蛤和共生体在不同的研究地点，使用分子方法。 通过探索一个潜在的不那么严格的共生可能有利于在不断变化的环境中生存，人们希望在丰富的环境中的作用和最终的环境影响的thyasirid蛤将变得清晰。 这项工作对于海洋生物学家、政府决策者和参与监测有机富集沉积物的科学家来说应该是重要的;因此，这项研究预计将通过更好地了解那些适应在受干扰的海洋沉积物中生活的独特物种的作用，使所有加拿大人受益。

In marine sediments highly enriched with organic matter (e.g. near pulp and paper mill or sewage outfalls, aquaculture pens, agricultural sites, and gas and oil fields), microbes degrade organic matter, producing toxic reduced sulphur; organic enrichment is recognized as being one of the greatest problems facing coastal environments worldwide. A particular group of small, poorly-known clams (bivalve family Thyasiridae) is often among the first and most abundant colonists of enriched environments, including in several sites along the Canadian coastline. Those thyasirid clams are able to thrive in enriched environments with the help of symbiotic, sulphur-oxidizing bacteria living in their gills; bacterial symbionts are an additional food source for the clams. As opposed to other animals with similar symbioses from deep-sea hydrothermal vents, cold seeps or whale falls, thyasirids do not keep their bacterial symbionts within gill cells, but outside them (extracellularly). My research uses cutting-edge observational techniques to study the particularities of extracellular symbiosis in thyasirid clams, and how it affects the nutritional input they gain from the association. Also, I focus on the variability in symbiont abundance between different sites, and I use experiments in which nutritional inputs to the host and symbiont are manipulated, to determine the impacts on the clams. Finally, I study the identity of the clams and symbionts in different study sites, using molecular approaches. By exploring how a potentially less rigid symbiosis might be beneficial for surviving in changing environments, it is hoped that the role and eventual environmental impacts of thyasirid clams in enriched environments will become clear. This work should be important for marine biologists, government policy decision-makers, and scientists involved in the monitoring of organically enriched sediments; as such, this research is expected to benefit all Canadians through a better understanding of the role of those unique species that are adapted for living in disturbed marine sediments.