Facultative Feeding by Planktotrophic Larvae of Echinoids

在我们对海洋生物生殖和发育生态学的理解中，需要将生活史理论与浮游生物幼虫的功能分析相结合。 这种结合应证明是这些领域之间重要的综合联系。 一个核心问题是什么生态因素影响了幼虫的发育？ 对能量学的关注是重要的，因为这是生命史、生态学和进化的许多一般理论模型的核心。 该项目将通过评估在卵大小差异很大的一组密切相关、共同发生的棘球蚴中兼性摄食的后果，提供关于嗜食性幼虫发育的新信息。 传统上，海洋无脊椎动物幼体被分为两种相互排斥的、性质不同的营养类型：摄食型和非摄食型。大多数需要食物发育的幼虫被认为来自非常小的卵，并且在整个幼虫生命中需要食物。不取食的幼虫由非常大的卵黄卵发育而成，直到变态后才能获得或利用外源食物。许多生活史性状与营养模式相关，如卵大小、繁殖力、幼虫形态、发育时间和幼体大小。生活史特征的分布和幼虫策略的理论建模的经验观察导致了这样的观点，即两种营养模式的极端代表最成功的生殖策略。 最近的工作对海胆幼虫的摄食需求提出了挑战的预测，在海洋无脊椎动物的生殖策略的经典模型。一系列令人惊讶的“中间”战略，以前没有认识到，也没有预测，已被记录在案。在海胆（海胆和沙元）之间，存在着一个连续的喂养策略，幼虫在发育到变态所需食物的程度上有很大的不同。亲本在卵中提供的营养储备量与幼虫需要外源食物的阶段正相关。据预测，蛋的能量含量也决定了兼性摄食的能力，即，在内源性储备耗尽和必须进食之前获得外源性食物的能力。由于缺乏关于兼性幼虫摄食的信息，无法对幼虫策略差异的生态和进化影响进行有意义的评估。 该项目旨在评估兼性摄食的贡献，在嗜食性海胆幼虫。将采用两种方法。首先，实验室实验将被用来评估经验的贡献，兼性喂养的幼虫发育率和少年的能量含量在6个相关的，共同发生的物种，有不同的鸡蛋大小和不同的能力，在没有食物的情况下发展。其次，将构建新的幼虫发育和生长的理论模型，分析兼性喂养对不同水平的父母投资的相对优势的后果。这些研究的目的是产生新的信息的关系，海洋无脊椎动物之间的幼虫战略的多样性。

McEdward Advances in our understanding of the ecology of reproduction and development in marine organisms require combining life history theory with functional analyses of larvae as pelagic organisms. This combination should prove to be an important integrative link between these fields . A central question will be what ecological factors influence the development of feeding larvae? A concentration on energetics is important because this is central to many general theoretical models of life history ecology and evolution. This project will provide new information on the development of planktotrophic larvae by evaluating the consequences of facultative feeding in a closely related, co-occurring group of echinoids that differ widely in egg size. Traditionally marine invertebrate larvae have been classified into two mutually exclusive, qualitatively different nutritional types: feeding and non-feeding. Most larvae that require food for development are thought to come from very small eggs and require food throughout larval life. Non-feeding larvae develop from very large yolky eggs and cannot obtain or utilize exogenous food until after metamorphosis. Many life history traits are correlated with nutritional mode, such as egg size, fecundity, larval morphology, development time, and juvenile size. Empirical observations of the distribution of life history traits and theoretical modeling of larval strategies have led to the view that the extremes of the two nutritional patterns represent the most successful reproductive strategies. Recent work on the feeding requirements of echinoid larvae challenges the predictions made by the classic models of reproductive strategies in marine invertebrates. A surprising range of "intermediate" strategies that had not been recognized before, nor predicted, has been documented. Among echinoids (sea urchins and sand dollars) there exists a continuum of feeding strategies across which larvae vary substantially in the degree to which they require food for development to metamorphosis. The amount of nutritional reserves provided in the egg by the parent is positively correlated with the stage at which the larvae require exogenous food. It is predicted that egg energy content also determines the capacity for facultative feeding, i.e., the ability to acquire exogenous food before endogenous reserves are exhausted and feeding becomes obligatory. The lack of information on facultative larval feeding precludes a meaningful assessment of the ecological and evolutionary implications of differences in larval strategies. The project seeks to assess the contribution of facultative feeding in planktotrophic echinoid larvae. Two approaches will be used. First, laboratory experiments will be used to evaluate empirically the contribution of facultative feeding to larval development rate and juvenile energy content in six related, co-occurring species that have different egg sizes and different abilities to develop in the absence of food. Second, new theoretical models of larval development and growth will be constructed to analyze the consequences of facultative feeding on the relative advantages of different levels of parental investment. These studies are designed to generate new information on the relationships that underlie the diversity of larval strategies among marine invertebrates.