Collaborative Research: Evolution of Physical and Chemical Attributes of Gametes in Free Spawning Marine Invertebrates: A Functional and Phylogenetic Approach

合作研究：自由产卵海洋无脊椎动物配子物理和化学属性的进化：功能和系统发育方法

• 批准号: 9811121
• 负责人: Robert Podolsky
• 金额: $ 27.53万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-01-01 至 2003-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9811121&HistoricalAwards=false
• 关键词: Collaborative; Research; Evolution; Physical; Chemical

The goal of this project is to examine the evolutionary significance of gamete traits that influence fertilization success in free-spawning marine organisms. Basic research in this field is crucial for understanding the reproductive ecology of harvested invertebrates, for aquaculture and for conservation biological reasons. Recent work on the fertilization ecology of free-spawners has raised diverse questions regarding character evolution at the gamete stage of the life cycle. Theory and empirical studies suggest that the size of eggs and egg coats, the density of sperm receptor sites, the speed and longevity of sperm, and the action of sperm-activating compounds released by eggs can each influence fertilization success by affecting rates of sperm-egg contact. These studies, however, have not resolved whether particular traits are a product of selection on fertilization success, and whether such traits appear to co-evolve as a result of their functional interactions. This project will involve a set of at least 9 sympatric species of marine brittlestars in the genus Macrophiothrix (Echinodermata: Ophiuroidea) from coral reef ecosystems. This group includes at least 40-fold variation in egg volume and provides an ideal comparative system for assessing the importance of size and other gamete attributes in sperm-egg collision. Interest in this genus is especially motivated by our discovery of an unusual degree of species-specificity in sperm chemotaxis, which offers a unique opportunity to examine the role of sperm chemotaxis in promoting reproductive isolation. The research will integrate phylogenetic information, tests of fertilization performance, and measures of gamete attributes to address fundamental questions about the evolution and co-evolution of gamete traits. In order to test hypotheses about gamete function in a phylogenetic context, this study has the following four objectives: OBJECTIVE 1: To construct a phylogeny for the study species using molecular markers. Phylogenetic information is needed to establish historical patterns of character change, as well as to control for correlation among traits due to common ancestry. OBJECTIVE 2: To examine the importance of egg size and other physical gamete attributes in fertilization. In vitro fertilization assays and variation in gamete traits will be used to test the hypothesis that egg target size and sperm swimming speed contribute to interspecific variation in fertilization success. OBJECTIVE 3: To examine the role of spermegg chemical attraction in promoting reproductive isolation. OBJECTIVE 4: To test hypotheses concerning patterns of covariance among gamete traits. Phylogenetic information will be used to test hypotheses of coevolution where theory predicts functional interactions between pairs of traits: ovum size and jelly coat size; egg target size and sperm speed; sperm speed and longevity; egg target size and the strength of sperm chemotaxis. This research is designed to fill critical gaps in our understanding of fertilization ecology and the evolution of gamete characters. This will be a comprehensive study in a phylogenetic context of both physical and chemical traits that can influence rates of gamete contact . By using phylogenetic information for a closely-related group of ecologically similar organisms, this research explicitly tests evolutionary hypotheses about functional relationships among such traits. Furthermore, the unique pattern of sperm chemotaxis in this system provides an opportunity to examine the role of pre-contact chemical specificity in promoting the reproductive isolation of synchronously-spawning species. Because free-spawning is the dominant and likely ancestral mode of fertilization, results from this project will have widespread relevance to the evolution of reproductive systems in marine environments.

这个项目的目标是研究配子性状的进化意义，影响受精成功的自由产卵的海洋生物。 这一领域的基础研究对于了解收获的无脊椎动物的生殖生态、水产养殖和保护生物学原因至关重要。 最近的工作受精生态的自由产卵提出了各种各样的问题，在生命周期的配子阶段的性格进化。理论和实证研究表明，卵子和卵外壳的大小，精子受体位点的密度，精子的速度和寿命，以及卵子释放的精子激活化合物的作用，都可以通过影响精卵接触率来影响受精成功。然而，这些研究并没有解决特定性状是否是受精成功的选择产物，以及这些性状是否因其功能相互作用而共同进化。 该项目将涉及一组至少9种同域分布的珊瑚礁生态系统中的Macrophiothrix属（棘皮动物：蛇尾总科）海洋脆星。这一组包括至少40倍的变化，卵子体积，并提供了一个理想的比较系统，用于评估的重要性，大小和其他配子属性的精卵碰撞。 在这一属的兴趣是特别动机，我们发现了一个不寻常的程度的物种特异性精子趋化性，这提供了一个独特的机会来研究精子趋化性的作用，促进生殖隔离。该研究将整合系统发育信息，受精性能测试和配子属性的测量，以解决有关配子性状进化和共同进化的基本问题。为了验证配子功能在系统发育背景下的假设，本研究有以下四个目标：目标1：利用分子标记构建研究物种的系统发育。系统发育信息是建立历史模式的性格变化，以及控制性状之间的相关性，由于共同的祖先。目的2：研究卵子大小和其他物理配子属性在受精过程中的重要性。体外受精试验和配子性状的变化将被用来测试的假设，卵子的目标大小和精子游泳速度有助于种间变异受精成功。 目的3：研究speremegg化学吸引在促进生殖隔离中的作用。 目的4：检验关于配子性状之间协方差模式的假设。系统发育信息将被用来测试假设的共同进化理论预测功能之间的相互作用对性状：卵子大小和果冻外套大小;卵目标大小和精子速度;精子速度和寿命;卵目标大小和精子趋化性的强度。 这项研究旨在填补我们对受精生态学和配子特征进化的理解中的关键空白。这将是一个全面的研究，在系统发育的背景下，物理和化学性状，可以影响率的配子接触。通过使用系统发育信息的一组密切相关的生态相似的生物体，本研究明确测试这些特征之间的功能关系的进化假说。此外，在这个系统中的精子趋化性的独特模式提供了一个机会，以检查接触前的化学特异性，促进同步产卵物种的生殖隔离的作用。由于自由产卵是受精的主要和可能的祖先模式，从这个项目的结果将有广泛的相关性，在海洋环境中的生殖系统的演变。