Further Investigations on Larval Nutrition and its Influence on Juvenile Performance of Benthic Invertebrates: Competition, Thermal Stress, and Natural Populations

底栖无脊椎动物幼虫的营养状况及其对幼鱼性能（沉降后数天和数周内的生长和存活）的潜在影响是海洋生态学中几乎未被研究的领域。要进一步了解海洋（浮游生物）和底栖生物组成部分在许多海洋无脊椎动物复杂生命周期中的关系，就需要探索浮游生物幼虫的营养环境如何影响变质后的底栖幼体的表现。在这个课题的前3年的研究中，我们已经证明，在实验室中操纵的幼虫饮食导致了幼虫有机含量和大小的变化。此外，在野外条件下，饵料的操纵对新变态/成批底栖幼鱼的生长和存活有显著影响。本研究结合了对三种不同的无脊椎动物门（藤壶、海胆和蜗牛）幼体的实验室实验和实地研究，有助于关注海洋无脊椎动物的早期幼年生物学。增加对早期幼鱼的了解应有助于澄清幼虫供应和定居后过程在种群动态中的重要性，例如种群结构和海洋群落。这也可能揭示幼虫的营养状况是否会影响幼鱼到成年期的生存。在拟议的研究中，调查将确定幼虫营养史的变化如何影响幼鱼种内和种间的竞争相互作用。将研究在沿海和河口环境的潮间带和潮下生境中出现的许多不同的藤壶物种，从而探索在不同类型和程度的生境（温度、干燥、盐度和食物类型）中幼虫营养的影响。幼壶和成壶之间的竞争相互作用有很好的文献记载，但幼虫的营养史是否对竞争结果有影响尚不清楚。通过将幼鱼置于相互作用的环境中，这项工作将探索幼虫营养在田间条件下的影响，这些条件反映了许多物种自然种群的定居条件。这项工作的第二部分将研究幼虫的营养史如何影响幼体的其他特征，除了它们的生长和生存。测定幼鱼营养对幼鱼取食器大小、蜕皮率以及幼鱼对热应激的生化反应的影响。这些数据将显示幼虫饮食的形态和生理后果，并有助于我们理解为什么生长和生存受到影响。对于热应激的生理反应，将量化热休克蛋白（lisp 70's & 90's）和泛素偶联物（分别反映蛋白质可逆和不可逆损伤的蛋白质）的诱导。最后，我们将对我们已经进行了实验操作、竞争研究和生理学研究的同一藤壶的幼虫大小和能量含量的自然变异及其对幼鱼性能的影响进行研究。通过测量变形时的大小和跟踪自然沉降藤壶的表现，我们可以确定在实验室中创建的操作是否反映在自然种群中。对幼虫大小、有机含量和热应激蛋白表达的额外测量将有助于加入实验室和实地研究。将全年监测自然沉降，以寻找幼虫质量的季节性模式，以及幼虫质量是否持续影响幼鱼的表现。该项目将为海洋无脊椎动物幼鱼的生长和生存提供必要的经验数据，为了解幼鱼营养的作用提供更广阔的背景，并为进一步研究海洋无脊椎动物幼鱼生态学提供新的方法。

The nutritional condition of benthic invertebrate larvae and its potential influence on juvenile performance (growth and survival in the days and weeks after settlement) is an almost unstudied area of marine ecology. Further understanding of the connections between oceanic (planktonic) and benthic components of the complex life-cycles of many marine invertebrates will require exploration of how the nutritional environment of the planktonic larva affects the performance of the post-metamorphic, benthic juvenile. In the first 3 years of work on this topic, we have shown that larval diet, manipulated in the laboratory, resulted in changes in larval organic content and size. Furthermore manipulations of larval diet had significant influences on growth and survival of newly metamorphosed/batched benthic juveniles under field conditions. This research joined lab experiments and field studies on juveniles from three different invertebrate phyla (barnacles, sea urchins and snails) and should help focus attention on early juvenile biology of marine invertebrates. Increased understanding of early juveniles should help clarify the importance of larval supply and post-settlement processes in population dynamics such as structuring populations and marine communities. It may also reveal whether larval nutritional status affects survival of juveniles to adulthood.In the proposed research, investigations will determine how variations in larval nutritional history may affect intraspecific and interspecific competitive interactions among young juveniles. A number of different barnacle species that occur in intertidal and subtidal habitats in coastal and estuarine environments will be studied, thereby exploring influences of larval nutrition in habitats that vary in types and degrees of stresses (temperature, desiccation, and salinity, and types of food). Competitive interactions among juvenile and adult barnacles are well documented, but whether larval nutritional history has an influence on competitive outcome is unknown. By placing juveniles in interactive situations, this work will explore the influence of larval nutrition in field conditions that reflect settlement conditions in natural populations of many species.A second part of the work will examine how larval nutritional history effects other features of juveniles besides their growth and survival. Measurements will be made on the effects of larval nutritional on the size of the juvenile feeding apparatus and molt rate and on the biochemical response of juveniles to thermal stress. This data will show morphological and physiological consequences of larval diet and contribute to our understanding of why growth and survival are affected. For the physiological responses to thermal stress, the induction of heat shock proteins (lisp 70's & 90's) and ubiquitin-conjugates will be quantified, (proteins that reflect reversible and irreversible damage to proteins, respectively).Lastly, examinations of natural variation will be made for larval size and energy content and its affects on juvenile performance of the same barnacles for which we have conducted experimental manipulations, competition studies and physiological studies. By measuring size at metamorphosis and following performance of naturally settling barnacles we can determine whether the manipulations created in the laboratory are reflected among natural populations. Additional measures of larval size, organic content, and expression of thermal stress proteins will help join the laboratory and field-based studies. Natural settlement will be monitored throughout the year to look for seasonal patterns in larval quality and whether larval quality consistently influences juvenile performance.This project should provide much needed empirical data on juvenile growth and survival, a broader context for understanding the role of larval nutrition, and new methodologies for further experimental investigations of juvenile ecology of marine invertebrates.