Claw transformation in Alpheus involves changes in claw morphology, and in closer structure, neuromuscular physiology, and muscle biochemistry. We will pursue the mechanisms of these modifications at a cellular and at a molecular level. At the cellular level we will attempt to identify agents of change: motor pathways are essential for the observed modifications. We will launch a detailed search for the causative agent this will entail examination of pre- and postsynaptic electrical properties using both chronic and acute electrical recording techniques. Non- electrical signals important to muscle transformation expressed by motor neurons imply new chemical agents. The identity and cellular sources of this message will be sought. The specificity of target response is most likely due to differences in presence of hormone- specific receptors, either in the affected muscle fibers or in cells which themselves produce a muscle fiber-specific agent. To this end we will attempt, by radioassay, to identify receptors for 20-hydroxyecdysone, an arthropod growth hormone know to be effective in promoting molting and claw transformation in shrimps. The identification of specific cellular targets of the hormone, whether located in the muscle or within the nervous system, will be a central focus in our search for causative cellular agents. Finally, we hope to identify specific molecular mechanisms used to bring about the switch in Troponin T isoforms that accompanies claw transformation. Is this a transcriptional mechanism, or is it brought about post transcriptionally, for example, by alternate splicing.