Linking Bioturbation and Sensory Biology: Chemoreception Mechanisms in Deposit-Feeding Polychaetes

软沉积物底栖生境在海洋环境中普遍存在，其典型特征是大型动物组合，其中包括大量摄食沉积物的无脊椎动物，如多毛类、双壳类、腹足类、甲壳类、海参类和半角类。通过部分受化学感受调节的摄食，这些生物对其栖息地的生态、生物学、地质学和化学有深远的影响。然而，关于沉积物摄食者接受化学物质的生理学和分子生物学方面的知识却知之甚少。本研究是对沉积物摄食螺旋体多毛类中协调化学接收的感觉机制的综合研究。它直接解决了这种缺乏信息的问题，因此将对目前对多毛类和其他海洋无脊椎动物化学接收的理解产生重大影响。在三个目标中的第一个目标中，将使用电子显微镜和共聚焦显微镜来描述螺旋体多毛类触片上可能的感觉结构的超微结构和神经支配。其次，将通过行为分析和活性依赖细胞标记研究来测试PALP感觉细胞和颈部器官的趋化能力。行为分析将识别引起显著摄食反应的化学线索，并确定其阈值敏感度。补充性免疫细胞化学实验将确定(1)引起行为反应的化学物质是否激活目标1中描述的感觉细胞；(2)感觉细胞的敏感性(即刺激阈值)；(3)对特定化学提示做出反应的细胞的分布。第三，将使用功能生化方法来鉴定和分离与周围感觉细胞和颈部器官相关的候选化学感受器蛋白。这项研究的几个结果具有特别重要的意义。首先，细胞标记方法将进一步改进，用于小型无脊椎动物，并将为未来研究许多海洋无脊椎动物幼虫协调栖息地选择的神经机制提供强有力的工具。其次，序列信息和纯化的受体将为mRNA和抗体探针的开发奠定基础，这些探针可以用于检测多毛类和其他海洋无脊椎动物的基因表达和详细的化学感觉转导途径。这些信息将有助于研究无脊椎动物门之间的进化关系和感觉结构的进化。除了科学意义外，该项目还为研究生和本科生的培训提供了重要机会。三名K-12教育工作者或高中生也将通过缅因州教师和学生研究实习计划参加。他们的参与不仅增加了这一超额认购项目的能力，还加强了当地K-12社区与缅因州大学之间的联系。将创建以海洋环境中的感官感知和生态为重点的互联网活动和资源。这些材料将把研究扩大到更多的互联网受众，并促进将海洋科学实例纳入通常仅从陆地和人类角度处理的主题。

Soft-sediment benthic habitats are ubiquitous in the marine environment and typicallyfeature macrofaunal assemblages that include large numbers of deposit-feeding invertebratessuch as polychaetes, bivalves, gastropods, crustaceans, holothurians, and hemichordates. Viatheir feeding, modulated in part by chemoreception, these organisms have profound effects onthe ecology, biology, geology, and chemistry of their habitats. Very little is known, however,concerning the physiology and molecular biology of chemoreception in deposit feeders. This research is a comprehensive investigation of the sensory mechanisms coordinatingchemoreception in deposit feeding spionid polychaetes. It directly addresses this lack ofinformation and will therefore have a significant impact on the current understanding ofchemoreception in polychaetes and other marine invertebrates. In the first of three objectives, the ultrastructure and innervation of putative sensory structures on spionid polychaete palps will be described using electron and confocal microscopy. Second, the chemoreceptive capacity of palp sensory cells and nuchal organs will be tested withbehavioral assays and activity-dependent cell labeling studies. The behavioral assays will identify chemical cues that elicit significant feeding responses and establish their threshold sensitivities. Complementary immunocytochemistry experiments will determine (1) if the chemicals that elicit behavioral responses activate the sensory cells described in objective 1; (2) the sensitivity of the sensory cells (i.e., stimulation thresholds); and (3) the distribution of cells responding to a particular chemical cue. Third, a functional biochemical approach will be used to characterize and isolate candidate chemoreceptor proteins associated with the peripheral sensory cells and nuchal organs. Several outcomes of the research are of particular significance. First, the cell-labeling method will be further refined for use with small invertebrates, and will provide a powerful tool for future studies of the neural mechanisms coordinating habitat selection by many species of marine invertebrate larvae. Second, the sequence information and purified receptor will set the stage for development of mRNA and antibody probes that can be used to examine gene expression and detail the chemosensory transduction pathways in polychaetes and other marine invertebrates. Such information will be useful to researchers interested in the evolutionary relationships among invertebrate phyla and the in evolution of sensory structures. In addition to its scientific relevance, the project provides significant opportunities for graduate and undergraduate student training. Three K-12 educators or high school students will also participate through the Maine Research Internships for Teachers and Students program. Their participation not only increases the capacity of this over subscribed program, but also strengthens the links between the local K-12 community and the University of Maine. Internet activities and resources will be created that focus on sensory perception and ecology in the marine environment. These materials will extend the research to an even larger Internet audience and facilitate the incorporation of ocean science examples into topics typically approached only from a terrestrial and human perspective.