Feeding and food limitation in copepod nauplii, the neglected life stage

这个项目将调查海洋中最丰富的后生动物--桡足类无节幼虫的摄食情况。它将回答三个问题：1)在实验室里，当成年和无节幼体被喂养多个猎物物种时，它们的食物选择有什么不同？2)当成体和无节幼体以自然的猎物组合为食时，它们的食物选择有什么不同？3)当桡足类和无节幼体的生长受到食物限制时，它们的生长、发育和存活有什么不同？比较实验和实地测量将对比无节幼体和后期生命阶段所消耗的食物以及食物限制的影响。这种对比将包括食物的属性，如大小，分类和运动性，将包括培养的猎物单独或混合提供的实验，以及自然猎物，并应用遗传技术来确定捕食性桡足类动物对猎物的消耗。将从旧金山河口收集桡足类动物，选择四个物种进行实验，以跨越分类学群体、大小、盐度范围和一般摄食行为。将应用各种技术来解释每种技术不可避免的偏见和局限性；除一种外，所有技术都曾在我们的实验室应用过。这些将包括使用单独和混合培养的猎物进行的实验室喂养实验，以及使用天然猎物的实验。实验瓶中猎物的消耗量将通过显微镜和流式细胞仪的颗粒计数和叶绿素浓度来测量。放射性标记的猎物将在短期孵化中用于确定对特定猎物类型的摄食。来自现场的样本将被检查肠道荧光。单独的实验将确定无节幼体和桡足类如何在不同浓度的食物中生存和生长。对捕食性桡足类动物(Tortanus Dextriobatus)觅食的调查将使用分子技术来识别不同疑似猎物物种的线粒体和核DNA。将针对实验室中右旋毛虫摄食的常见浮游动物物种开发特定的引物。开发的通用引物和筛选方案将有助于识别其他河口群落中的食物网相互作用。桡足类无节幼体在海洋食物网中具有不同的营养作用，在桡足类的种群动态中也具有重要作用。无节幼体的摄食装置与后期完全不同，第一个摄食阶段对饥饿非常敏感，这使得这些生活阶段对种群动态至关重要。然而，现有的桡足类种群模型将无节幼体视为微型成虫。这项工作将为越来越多的海洋生态系统建模工作提供宝贵的投入。该项目还将支持旧金山州立大学的两篇硕士论文，旧金山州立大学是一所为少数族裔服务的机构。该项目将为包括URM学生在内的本科生提供持续的机会，在位于旧金山湾的Romberg Tiburon环境研究中心接受遗传学和田野生态学方面的培训，该中心是NSF FSML支持的野外站。

This project will investigate feeding by copepod nauplius larvae, the most abundant metazoans in the sea. It will answer three questions: 1) How does food selection by adults and nauplii differ when they are fed multiple prey species in the laboratory? 2) How does food selection by adults and nauplii differ when they are feeding on natural prey assemblages? and, 3) How do growth, development, and survival differ between copepodites and nauplii when their growth is food limited? Comparative experiments and field-based measurements will contrast the food consumed, and the effects of food limitation, between nauplii and later life stages. This contrast will include attributes of food such as size, taxon, and motility, and will include experiments with cultured prey offered singly or in a mixture, and natural prey, and apply genetic techniques to determine prey consumption by a predatory copepod. Copepods will be collected from the San Francisco Estuary, with four species selected for experiments to span taxonomic groups, sizes, salinity ranges, and general feeding behavior. A variety of techniques will be applied to account for the inevitable biases and limitations of each; all but one have previously been applied in our laboratories. These will include laboratory feeding experiments using cultured prey individually and in mixtures, and experiments using natural prey. Consumption of prey in experimental bottles will be measured as chlorophyll concentration and through particle counts by microscopy and flow cytometry. Radioactively labeled prey will be used in short incubations to determine feeding on particular prey types. Samples from the field will be examined for gut fluorescence. Separate experiments will determine how nauplii and copepodites survive and grow at different concentrations of food. Investigations of feeding by a predatory copepod (Tortanus dextrilobatus) will use molecular techniques to identify mitochondrial and nuclear DNA from diverse suspected prey species. Specific primers will be developed for common zooplankton species consumed by T. dextrilobatus in the laboratory. General primers and screening protocols developed here will be useful for identifying food web interactions in other estuarine communities.Copepod nauplii are important both in their diverse trophic roles in ocean foodwebs and in the population dynamics of copepods. Nauplii have a completely different feeding apparatus from later stages, and the first feeding stage can be very sensitive to starvation, making these life stages critical to population dynamics. Yet extant copepod population models treat nauplii as miniature adults. This work will provide valuable input to the growing efforts at modeling ocean ecosystems. This project will also support two Master's theses at San Francisco State University, a minority-serving institution. The project will provide continuing opportunities for training undergraduates, including URM students, in genetics and field ecology at the Romberg Tiburon Center for Environmental studies, an NSF FSML-supported field station on San Francisco Bay.