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.
