Functional Mechanisms of Control in the Bivalve Pump: an Experimental Approach to Resolve Current Controversy

双阀泵的功能控制机制：解决电流控制的实验方法Evan Ward和Sandra Shumway在康涅狄格大学双壳类软体动物(例如，蛤、牡蛎、扇贝)几乎在所有深度的海洋、河口和淡水环境中都能找到。这些生物通过过滤周围水中的颗粒物来获取食物。它们具有高效和复杂的提取这些颗粒的机制，因此在耦合水柱和底部群落方面具有重要的生态学意义。它们极大地控制着许多沿海生态系统中颗粒(它们的食物)的供应和分布，因此可以影响其他生物的总体福祉以及整个环境。由于这些生物在生态系统中扮演着如此关键的角色，因此了解它们如何获得和处理食物和非食物颗粒，以及摄食过程的内在和外在控制是很重要的。研究双壳类摄食过程的能力已经与分析设备的进步和应用联系在一起。这些研究人员在与悬浮喂食器相关的研究中率先使用了两种系统，即流式细胞仪和视频内窥镜。通过这样做，他们极大地增加了我们对几组悬浮喂食器中颗粒捕获、运输、拒绝和摄取的喂食结构和运动学的功能形态的理解。在这项研究中，将使用两项新技术，一种新开发的压力-间隙系统和粒子图像测速(PIV)。这些方法将加深我们对双壳类软体动物水处理的生理基础，即抽水和过滤的理解。这项研究分为三个主要项目，将考察三种双壳类的摄食情况，每种双壳类都有特定的鳃结构：蓝贻贝(Mytilus Edulis)、东方牡蛎(Crassostrea Virgiica)和海扇贝(Placopecten Magellanicus)。总体目标是：1)利用新开发的技术在生物体和器官水平上研究悬浮饲养双壳贝水处理的作用机制，以及2)检验现有双壳贝类抽水性能模型的关键假设。实验的目的是：a)确定泵送压力和速率(体积流量)之间的关系，以获得关于三个双壳类物种泵送特性的基线数据；b)通过检查潜在的控制位置，例如纤毛活动、瓣膜张口、鳃收缩的变化，来研究双壳类改变泵送活动的机制；c)检验双壳类泵送活动是一个二元过程(开/关)或自主过程的假设；d)测试双壳类抽水活动是由外部因素调节的假说，例如食物的数量和质量，并且受到补偿控制；E)研究三种双壳类在抽水行为和性能方面的差异。这项研究有可能解决一些长期存在的关于双壳类水处理的生理基础的争议，并为其他悬浮摄食性无脊椎动物的这些过程的研究提供一个起点。这种方法的独特之处在于，研究人员正在整合几种技术，在器官和有机体水平上研究与基本过程--过滤喂养--相关的机制。研究人员将能够将这些发现与动物在自然环境中的表现联系起来。研究生和本科生将参与学习的所有方面，并鼓励女性和代表性不足的少数民族参与。

Functional Mechanisms of Control in the Bivalve Pump:An Experimental Approach to Resolve Current ControversyJ. Evan Ward and Sandra ShumwayUniversity of ConnecticutBivalve molluscs (e.g., clams, oysters, scallops) are found in almost all depths in marine,estuarine and freshwater environments. These organisms obtain their food by filtering particles from the water surrounding them. They possess highly efficient and complicated mechanisms for extracting these particles, and therefore are significant ecologically in coupling water-column and bottom communities. They exert great control over the supply and distribution of particles (their food) in many coastal ecosystems, and thus can influence the general well-being of other organisms as well as the overall environment. Because these organisms play such a key role in ecosystems, it is important to understand how they obtain and process food and non-food particles, and the intrinsic and extrinsic controls of the feeding process. The ability to study feeding processes of bivalves has been linked with advances and application of analytical equipment. These investigators have pioneered the use of two systems, flow cytometry and video endoscopy, in studies related to suspension feeders. In doing so, they have greatly increased our understanding of the functional morphology of feeding structures and kinematics of particle capture, transport, rejection, and ingestion in several groups of suspension feeders. In the present study, two new techniques will be used, a newly developed Pressure-Gape System and Particle Image Velocimetry (PIV). These methods will further our understanding of the physiological bases of water processing, i.e. pumping and filtration, in bivalve molluscs. The research is divided into three major projects and will examine feeding in three species of bivalves, each with a specific gill structure: blue mussels (Mytilus edulis), eastern oysters (Crassostrea virginica) and sea scallops (Placopecten magellanicus). The overall objectives are to: 1) Investigate the functional mechanisms of water processing in suspension feeding bivalves at levels of both the organism and organ using newly developed techniques, and 2) Test key assumptions of existing models of water-pumping performance in bivalves. Experiments are designed to: a) Determine relationships between pumping pressure and rate (volume flux) to obtain base-line data on pumping characteristics for the three bivalve species; b) Investigate mechanisms by which bivalves alter pumping activity by examining potential loci for control, e.g. changes in lateral cilia activity, valve gape, contractions of the gill; c) Test the hypotheses that bivalve pumping activity is a binary process (on/off), or an autonomous process; d) Test the hypothesis that bivalve pumping activity is mediated by exogenous factors, such as food quantity and quality, and is under compensatory control; e) Examine the variation in pumping behavior and performance among the three bivalve species. This research has the potential to resolve some of the long-standing controversies regarding the physiological basis of water processing in bivalves, and to provide a starting point for the study of these processes in other suspension-feeding invertebrates. The approach is unique in that the researchers are integrating several techniques to study mechanisms associated with a fundamental process, filter feeding, at both the organ and organism level. The researchers will be able to relate these findings to performance by the animals in the natural environment. Graduate and undergraduate students will be involved in all aspects of the study and participation by females and underrepresented minorities will be encouraged.