Activation and Regulation of Metamorphosis in a Molluscan Larva

变态是由一系列戏剧性的、暂时压缩的发育事件组成的，包括细胞死亡、细胞运动、细胞分裂和组织转化。因此，它为同时研究提供了许多发展过程。关于两栖动物和昆虫变态发育时内分泌控制的知识是广泛的。然而，大多数具有变态发育的动物物种是海洋无脊椎动物，而且大多数海洋无脊椎动物是由外部而非激素触发的变态。本文描述的研究将利用海蛞蝓Phestilla sibogae进一步探索幼虫内部外部诱导变态激活的机制。由于它们作为这类研究的模型已被证明具有实用价值，因此小孢子虫的幼虫将作为体外研究其变态启动（即能力）及其特定化学敏感性的组织来源。神经生理学实验将用于定位和表征神经元和神经机制，这些神经元和神经机制在整个幼虫中引起组织特异性反应。在完成这些研究后，哈德菲尔德博士应该对诱导途径有足够的了解，以便开始检查最终导致变态的细胞内反应。有成千上万的海洋无脊椎动物会经历变态。与昆虫和两栖动物相比，这些物种对这一过程的了解非常少。目前的建议是继续研究一种这样的海洋无脊椎动物模型的变态。

Metamorphosis consists of a dramatic, temporally compressed series of developmental events that includes cell death, cell movement, cell division, and tissue transformation. It thus offers numerous developmental processes for simultaneous study. Knowledge of the developmentally timed endocrine control of metamorphosis in amphibians and insects is extensive. However, most of the animal species with metamorphic development are marine invertebrates, and most marine invertebrates have externally, not hormonally, triggered metamorphoses. The research described here will utilize the marine slug Phestilla sibogae to explore further the mechanisms by which externally induced metamorphosis is activated within the larva. Because of their proven utility as a model for such studies, larvae of Phestilla will serve as a source of tissues for in vitro investigation of their priming for metamorphosis (i.e. competence) and their specific chemical sensitivities. Neurophysiological experiments will be used to locate and characterize the neurons and nervous mechanisms that bring abut tissue-specific responses throughout the larva. At the completion of these studies Dr. Hadfield should have sufficient understanding of the inductive pathway to begin examination of the intracellular responses that culminate in metamorphosis. %%% There are hundreds of thousands of marine invertebrate species which undergo metamorphosis. The understanding of this process in any of these species is very slight compared to that in insects and amphibians. The current proposal is to continue a study of metamorphosis in one such model marine invertebrate.