RUI: Feeding by the ciliated larvae of marine invertebrates: effects of diverse particle capture mechanisms on feeding performance

许多海洋无脊椎动物的幼虫必须通过摄食来促进从变态到幼年阶段的发育。这些进食的幼虫以不同的方式捕捉悬浮的食物颗粒。实验室证据表明，不同的幼虫取食机制可能会根据颗粒类型影响其性能。例如，棘皮动物的幼虫通过纤毛反转进食，这种机制显然限制了对小颗粒（直径10微米）的清除率。相比之下，软体动物幼虫使用相反的纤毛带进食，这限制了对较大颗粒（10微米）的清除率。由于悬浮食物颗粒的浓度会限制天然水域中幼虫的生长，并且由于天然颗粒的大小分布随空间和时间的变化而变化，因此特定摄食机制所施加的最大清除率可能会限制幼虫的生长速度和发育。因此，悬食幼虫的浮游期会延长，幼虫的死亡率（由于被捕食或从合适的成虫栖息地平流）会增加，导致招募减少。这样，与特定的幼虫取食机制相关的性能限制可能会强烈影响种群动态。这种效应在底栖无脊椎动物种群动态模型中是缺失的，很大程度上是因为它们还没有被很好地理解。为此，需要对不同取食机制的纤毛虫幼虫的取食能力进行对照比较。本研究将研究使用三种颗粒捕获机制之一（纤毛逆转、对偶带或对偶带摄食和大颗粒偶遇摄食的“混合”策略）收集食物的幼虫的摄食能力，以及具有不同体型的幼虫（例如，在对偶带摄食中，trochophores与veligers）。将检验三个主要假设。(1)不同颗粒捕获机制/体型的幼虫在最大清除率或高清除率颗粒的大小谱上也存在差异。实验室实验将涉及人工颗粒，只是大小不同。(2)(1)的假设差异也适用于自然粒子。实验将测试半自然的猎物群落。(3)不同取食机制的幼虫在特定的取食环境（如小颗粒与大颗粒为主的取食环境）中表现最佳。幼虫的生长速度将在经过实验操纵的半天然食物体系中进行测试。智力优势：通过对幼虫摄食机制、幼虫体型和颗粒类型对幼虫性能的影响进行明确、有计划的比较，本研究将提高对幼虫摄食机制在海洋无脊椎动物种群动态中的重要性的认识。该研究涉及生殖生物学、生态学和进化中的许多重要问题，如：颗粒食物类型的季节性变化如何影响具有特定摄食机制的幼虫的生产性能；这种联系如何与不同海洋无脊椎动物分类群的季节性繁殖模式的进化有关；人类介导的海洋温度和化学变化（预计会改变潜在食物颗粒的大小谱）如何影响具有特定摄食机制的幼虫的表现？更广泛的影响：本项目将在整合研究和教育以及增加代表性不足群体对科学的参与方面产生重大的更广泛的影响。大量研究表明，密集的本科研究经历与随后在生物学等STEM职业中的参与和成功相关。本项目将为8-10名本科生和1名研究生提供这样的体验，他们将得到本项目的支持。其他学生研究人员将利用科罗拉多州立大学长滩分校和周五港实验室（UW）的现有项目获得支持，这些项目专注于增强生物学中的文化多样性。研究助理将接受幼虫生物学和实验方法方面的培训，并将设计和执行直接有助于实现提案目标的项目。他们将在科学会议上展示他们的研究成果，并作为同行评议论文的共同作者。作为该项目的一部分所购买的设备也将用于重新设计科罗拉多州立大学长滩分校的几门本科课程的实验室。此外，作为该项目的一部分，PI和学生将创建一个免费提供的网站，汇编有关加利福尼亚海洋无脊椎动物繁殖和幼虫生物学的数据，这对该地区的生物学家来说是一个独特而宝贵的资源。

Many marine invertebrate larvae must feed to fuel development through metamorphosis to the juvenile stage. These feeding larvae capture suspended food particles in diverse ways. Laboratory evidence suggests that different larval feeding mechanisms may affect performance depending on particle types. For example, larvae of echinoderms feed by ciliary reversal, a mechanism that apparently limits clearance rates on small particles (10 um diameter). In contrast, mollusk larvae feed using opposed bands of cilia, which limits clearance rates on larger particles (10 um). Because the concentration of suspended food particles can constrain larval growth in natural waters, and because the size distribution of natural particles varies over space and time, maximum clearance rates imposed by a particular feeding mechanism may restrict larval growth rates and development. As a result, the planktonic period of suspension-feeding larvae would be extended and larval mortality (due to predation, or advection from suitable adult habitat) increased, leading to lower recruitment. In this way, performance constraints associated with particular larval feeding mechanisms could strongly affect population dynamics. Such effects are missing from population-dynamic models of benthic invertebrates, largely because they are not well understood. Toward this end, controlled comparisons are needed of the feeding capabilities of ciliated larvae that differ in feeding mechanism. The present study will examine the feeding capabilities of larvae that gather food using one of three particle capture mechanisms (ciliary reversal, opposed band, or a "mixed" strategy of opposed band feeding and encounter feeding on large particles), and for larvae with distinct body forms (e.g., within opposed band feeding, trochophores vs. veligers). Three main hypotheses will be tested. (1) Larvae that differ in particle capture mechanisms/body form will also differ in either maximum clearance rates, or in the size spectrum of particles cleared at high rates. Laboratory experiments will involve artificial particles, varying only in size. (2) Hypothesized differences in (1) also hold for natural particles. Experiments will test semi-natural prey communities. (3) Larvae with different feeding mechanisms will perform best in specific feeding environments (e.g., those dominated by small particles versus large particles). Larval growth rates will be tested in experimentally manipulated, semi-natural food regimes. Intellectual merit: Yielding explicit, planned comparisons of larval performance as a function of feeding mechanism, larval body form, and particle type, this research would improve understanding of the importance of larval feeding mechanism in the population dynamics of marine invertebrates. This study is relevant to many compelling questions in reproductive biology, ecology and evolution, such as: how do seasonal changes in the types of particulate food affect the performance of larvae with particular feeding mechanisms; how might such linkages be related to the evolution of seasonal reproductive patterns in various taxa of marine invertebrates; and how might human-mediated shifts in ocean temperature and chemistry (predicted to alter the size spectrum of potential food particles) affect performance of larvae with particular feeding mechanisms? Broader impacts: This project will have significant broader impacts in integrating research and education, and in increasing the participation of underrepresented groups in science. Substantial research has shown that intense undergraduate research experiences are correlated with subsequent engagement and success in STEM careers like biology. This project will provide such experiences for 8-10 undergraduates and one graduate student, who will be supported by this project. Additional student researchers will be supported using existing programs at CSU Long Beach and the Friday Harbor Laboratories (UW) that focus on enhancing cultural diversity in biology. Research assistants will be trained in larval biology and experimental methods, and will design and carry out projects that contribute directly to addressing the proposal's goals. They will present their results at scientific meetings, and as coauthors of peer-reviewed papers. Equipment purchased as part of this project also will be used to redesign labs in several CSU Long Beach undergraduate courses. Moreover, as part of this project, the PI and students will create a freely available web site compiling data on the reproductive and larval biology of California marine invertebrates, a unique and valuable resource for biologists in the region.