The Fast Block to Polyspermy

多精卵通常在胚胎发育异常一小段时间后死亡，但许多动物和至少两种植物的卵子通过“快”和“慢”块保护免受多精。这里提出的研究将以岩藻为模型系统，扩展对快速阻塞(一种瞬时的、离子介导的阻塞)的一般理解。生理学和电生理学技术将被用来描述FAST块的离子依赖性和受精潜力。将在几种岩藻物种中评估精子/卵子比例对多精受精的影响，并收集野外受精和精子/卵子比例的数据。多精受精的自然水平将通过将瓷砖放置在潮间带的适当部分并观察定植受精卵的发育来确定。这类研究将考察在自然渗透胁迫期间，受精卵的招募受到快速阻断失败的影响的可能性。关于植物中多精块的信息很少。拟议的工作将通过拟议的岩藻研究以及通过检查其他几种海洋和淡水藻类是否存在离子块到多精受精，在这一领域做出重大贡献。由多个精子受精的卵子通常会在短时间的异常胚胎发生后死亡。在许多生物中，多精受精受到两种连续机制的阻止--一种是快速起作用的机制，另一种是慢速起作用的机制。快速阻断是由第一次受精后立即开始的瞬时离子通量所调节的。尽管它广泛存在，但几乎没有生态学数据来评估这种快速阻断在自然环境下的重要性，而不是在实验室中，那里的离子条件受到操纵，或者精子/卵子的比例很高。布劳利博士建议使用潮汐水池中的岩藻来研究自然情况，因为潮汐水池的离子条件可能会有很大的变化。因此，她将获得目前缺乏自然精子/卵子浓度的生态数据，以及对自然界中多精受精的普遍程度的评估。

Polyspermic eggs usually die after a short period of abnormal embryogenesis, but eggs of many animals and at least two plants are protected from polyspermy by "fast" and "slow" blocks. The studies proposed here will extend out general understanding of the fast block (a transient, ion-mediated blockage) using fucoid algae as a model system. Physiological and electrophysiological techniques will be used to describe the ionic dependence of the fast block and the fertilization potential. The effect of the sperm/egg ratio on polyspermy will be evaluated in several fucoid species, and data on fertilization and sperm/egg rations in the field will be collected. Natural levels of polyspermy will be determined by placing tiles within appropriate portions of the intertidal zone and observing the development of colonizing zygotes. Such studies will examine the possibility that recruitment of zygotes is affected by failure of the fast block during periods of natural osmotic stress. Little information is available on polyspermic blocks in plants. The proposed work will make a significant contribution in this area, both through the proposed studies of fucoid algae and by examining several other marine and freshwater algae for the presence of an ionic block to polyspermy. %%% Eggs that are fertilized by more than one sperm usually die after a short period of abnormal embryogenesis. In many organisms polyspermy is prevented by two successive mechanisms- a fast acting block and a slower one. The fast block is mediated by transient ionic fluxes that begin immediately after the first fertilization. In spite of its widespread occurrence, there is little ecological data available to evaluate the importance of this fast block under natural circumstances as opposed to in the laboratory where ionic conditions are manipulated or sperm/egg ratios are high. Dr. Brawley proposes to investigate the natural situation using fucoid algae in tide pools where ionic conditions can vary dramatically. She will thus obtain ecological data that are currently lacking on natural sperm/egg concentrations, and an evaluation of how common polyspermy is in nature.