Variation in Sex Expression in a Marine Bryozoan

雌雄同体现象在无根的海洋苔藓虫中很少被了解，这些苔藓虫将精子释放到外部进行受精和繁殖。本项目旨在探讨海洋苔藓虫雄性生殖成功与雄性生殖努力之间的关系，并最终与雌雄同体的进化有关。雌雄同体的海洋苔藓虫透明小虫在缅因州中部海岸研究的种群中表现出广泛的雄性和雌性表达差异。相对于雌性的生殖功能，个体群体在解剖学结构分配给雄性的数量上有所不同。本研究将利用这种多态性来检验雌雄同体进化维持的理论机制。该研究将解决三个具体目标：(1)在苔藓虫中开发可用于父系分析的遗传标记，(2)确定性别变异是否具有任何可测量的繁殖成功，(3)使用自然发生的“雌性”苔藓虫变体进行受精成功的独立分析。这项研究将首次尝试测试底栖海洋动物同时雌雄同体的性别分配模型。虽然这项研究不会分离苔藓虫的组合性别机制，但它将提供对该机制有效性的评估，这是底栖无脊椎动物生殖生态学中一个鲜为人知的方面。

Hermaphroditism is poorly understood in sessile marine Bryozoa that release of sperm externally for fertilization and reproduction. This project is designed to explore in a marine bryozoan how male reproductive success is related to male reproductive effort, and ultimately to the evolution of hermaphroditism. The hermaphroditic marine bryozoan Celleporella hyalina displays extensive variation in the expression of male and female gender in populations studied along the mid-coast of Maine. Individual colonies vary quantitatively in the allocation of anatomical structures to male relative to female reproductive functions. This investigation will use this polymorphism to test theoretical mechanisms for evolutionary maintenance of hermaphroditism. The study will address three specific objectives: (1) to develop genetic markers in the bryozoan that can be used in paternity analysis, (2) to determine whether gender variation has any measurable reproductive success, and (3) to use naturally-occurring "female" variants of the bryozoan in independent assays for fertilization success. This study will represent the first attempt to test sex allocation models for the presence of simultaneous hermaphroditism in benthic marine animals. Although this study will not isolate the mechanism of combined gender in bryozoans, it will provide an evaluation of the validity of this mechanism, a poorly understood aspect of benthic invertebrate reproductive ecology.