Collaborative Research: Adaptation of daphniids to digestion resistant resources

无脊椎动物对藻类的消耗是所有水生生态系统（湖泊、溪流和海洋）食物网中一个关键但知之甚少的环节。 先前的研究表明，这些无脊椎食草动物的生产力，以及包括渔业在内的其他食物网的生产力，往往受到藻类食物质量的限制。 在湖泊的开阔水域，藻类食物质量的主要决定因素是它们在食草动物肠道中的消化阻力。 虽然人们早就知道，一些藻类可能会毫发无伤地穿过小型无脊椎动物的肠道，但这种防御机制与食物网生态学和食草动物进化生物学的广泛相关性却被忽视了。 这项研究的主要目标将是研究的抗藻类的食草动物消化的生理，以量化的程度不同的食草动物物种的能力，克服消化防御，并通过实验测试的重要性，这种食草动物藻类相互作用的水生食物网的功能。一般的研究方法将集中在一个容易研究的生物体，也是一个主要的食草藻类在湖泊的开放水域：水蚤。 本研究将利用不同消化抗性的人工养殖和天然藻类，测量水蚤类食草动物的摄食率、肠道加工、呼吸、同化和生长。 几个物种，代表的daphniids内的多样性的广度，将在不同的动物年龄从少年到成年人进行研究。 最后，在食草动物消化生理变化的生态后果将使用大规模的封闭实验在一个天然湖泊进行检查。 该实验将操纵食草动物物种，并测试食草动物消化生理影响食草动物和藻类在lakes.This研究的种群动态的假设是创新的，探索在生态学上的关键群体的食草动物的摄食和肠道加工的多样性，并在测试这种生理多样性的后果，食物网功能。 尽管它们在湖泊的开放水域中扮演着主导食草动物的角色，但人们对水蚤如何消化自然界中的藻类知之甚少。 同样，虽然已知藻类在消化抗性方面各不相同，但对食草动物如何适应这种防御却知之甚少。 本研究的目的是通过研究限制水生生态系统中食藻相互作用的生态学和进化生理学来解决这两个问题，并强调对本科生和研究生进行生理学和生态学接口的培训。 拟议的工作还将继续一个主要的本科院校和一个研究密集型实地站之间的研究和培训伙伴关系，并提供全年的本科生参与实验室和实地研究，将生物体生理学与食物网的结构和功能联系起来。

The consumption of algae by invertebrates is a critical but poorly understood link in the food webs of all aquatic ecosystems: lakes, streams and oceans. Previous research has shown that the productivity of these invertebrate grazers, and hence the productivity of the rest of the food web including the fisheries, is often limited by the quality of the algal food. In the open water of lakes, a major determinate of algal food quality is their resistance to digestion while in the gut of the grazer. While it has been long known that some algae may pass unharmed through the guts of small invertebrates, the broad relevance of this defense mechanism to food web ecology and to the evolutionary biology of the grazers has been ignored. Major goals of this research will be to examine the physiology of grazer digestion of resistant algae, to quantify the extent to which grazer species vary in ability to overcome digestion defenses, and to experimentally test the importance of this grazer-algae interaction to the functioning of aquatic food webs. The general research approach will be to focus on an easily studied organism that is also a major grazer of algae in the open water of lakes: daphniids. Using both cultured and natural algae that differ in digestion resistance, this research will measure feeding rate, gut processing, respiration, assimilation, and growth of daphniid grazers. Several species, representing the breadth of diversity within the daphniids, will be studied at various animal ages from juvenile to adult. Finally, the ecological consequences of variation in grazer digestive physiology will be examined using a large-scale enclosure experiment in a natural lake. The experiment will manipulate grazer species and test the hypothesis that grazer digestive physiology influences population dynamics of grazers and algae in lakes.This research is innovative in exploring the diversity of feeding and gut processing in an ecologically key group of grazers, and in testing the consequences of this physiological diversity to food web function. Despite their role as dominate grazers in the open water of lakes, there is little understanding of how daphniids digest algae in nature. Similarly, while it is known that algae vary in digestion resistance, there is little understanding of how grazers adapt to such defenses. It is the general aim of this research to address these two deficiencies by studying the ecological and evolutionary physiology that constrains grazer-algal interactions in aquatic ecosystems.Training of undergraduates and graduates at the interface of physiology and ecology is emphasized in this research. The proposed work will also continue a research and training partnership between a primarily undergraduate institution and a research-intensive field station, and provide for year-round undergraduate involvement in laboratory and field studies that link organism physiology to the structure and function of food webs.