RUI: Assessing the Chemical Defenses of Caribbean Invertebrates

海绵、柳珊瑚和海鞘是海洋底栖生物群落的重要组成部分，尤其是珊瑚礁。它们组织的有机提取物产生了大量不寻常的化合物，这些化合物不参与初级代谢，它们的生物学功能大多是未知的。一种普遍持有的理论是，这些化合物对潜在的捕食者来说是令人厌恶的，但它们也可以防止污染或过度生长。这项研究是一个非常成功的RUI研究项目的延续，该项目旨在评估加勒比海海绵的防御能力，这一群体的分类和化学成分已经得到了很好的描述。由于礁海绵、柳珊瑚和海鞘数量丰富、结实、复杂的结构和化学防御，并且受到多面手和专业捕食者的放牧，它们为检验陆地生态学家提出的关于植物防御机制的基本假设提供了一个有用的群体。反掠食性结构和化学防御的研究将从以前的研究扩展到包括加勒比柳珊瑚和海鞘，使用以前应用于海绵的成功技术。特别是，最佳防御理论将在海鞘中进行测试，海鞘阐述了无机和有机化学防御。产生威慑性粗提取物的无脊椎动物物种的代谢物将通过生物测定定向分离来鉴定，从而更好地理解化学防御的结构-功能关系。将检查代谢物表达的种内模式，以确定它们是否符合最佳防御理论。关于防御性化学与生长、繁殖和再生之间资源分配的假设将通过操纵化学防御和非防御的珊瑚礁海绵在野外进行测试。鱼类捕食限制了海绵在珊瑚礁上分布的假设将通过比较来自吃海绵鱼类丰富的珊瑚礁（巴哈马群岛，佛罗里达群岛）和由于自然原因（百慕大）或人为原因（牙买加，巴巴多斯）鱼类捕食者稀少的珊瑚礁的样带数据来验证。海绵次生代谢物具有防污和抗过度生长防御功能的假设将在现场和实验室中通过凝胶法进一步验证，这些技术将用于分离活性代谢物。将进行实地实验，以确定海绵将活性代谢物表达到其表面或进入海水的速率。总体而言，该研究项目将继续开展热带无脊椎动物化学防御的最系统和最完整的调查之一，同时为RUI机构的学生提供重要的教育机会。这些结果将有助于判断从陆地生态系统研究中得出的化学防御理论的普遍适用性，同时促进我们对珊瑚礁环境中底栖无脊椎动物及其捕食者和竞争对手之间复杂关系的理解。

Sponges, gorgonians, and ascidians are important components of benthic marine communities, particularly coral reefs. Organic extracts of their tissues have yielded a wealth of unusual chemical compounds that are not involved in primary metabolism, and their biological functions are mostly unknown. One commonly held theory is that these compounds are distasteful to potential predators, but they may also protect from fouling or overgrowth. This study is a continuation of a very successful RUI research program designed to assess the defenses of Caribbean sponges, a group whose taxonomy and chemistry is fairly well described. Because reef sponges, gorgonians and ascidians are abundant, sessile, elaborate putative structural and chemical defenses, and are subject to grazing from generalist and specialist predators, they provide a useful group for testing fundamental hypotheses proposed by terrestrial ecologists about plant defensive mechanisms.Investigations of antipredatory structural and chemical defenses will be extended from the previous study to include Caribbean gorgonians and ascidians, using the successful techniques previously applied to sponges. In particular, optimal defense theory will be tested with ascidians, which elaborate both inorganic and organic chemical defenses. Metabolites of invertebrate species that have yielded deterrent crude extracts will be identified by bioassay-directed fractionation, resulting in a better understanding of the structure-function relationships of chemical defenses. Intraspecific patterns of metabolite expression will be examined to determine whether they conform to optimal defense theory. Hypotheses regarding resource allocation between defensive chemistry and growth, reproduction, and regeneration will be tested by manipulating chemically defended and non-defended reef sponges in the field. The hypothesis that fish predation limits sponge distributions on reefs will be tested by comparing transect data from reefs where sponge-eating fishes are abundant (Bahamas, Florida Keys) to reefs where fish predators are rare due to natural (Bermuda) or anthropogenic causes (Jamaica, Barbados). The hypothesis that sponge secondary metabolites function as antifouling and anti-overgrowth defenses will be further tested in the field and laboratory with gel-based assays, and these techniques will be used to isolate the active metabolites. Field experiments will be conducted to determine the rates at which active metabolites are expressed by sponges onto their surfaces or into seawater.Overall, this research program will continue to develop one of the most systematic and complete investigations of chemical defenses of tropical invertebrates, while at the same time providing important educational opportunities for students at an RUI institution. The results will be useful in judging the general applicability of chemical defense theories derived from studies of terrestrial ecosystems, while advancing our understanding of the complex relationships between benthic invertebrates, their predators and their competitors in coral reef environments.