Characterization of Chemosensory Pathways in Cnidarians

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Characterization of Chemosensory Pathways in CnidariansP. Anderson, IBN 0110550ABSTRACT The ability to detect and respond to chemical stimuli is a fundamental property of all organisms, and in metazoan animals, specialized sensory structures (chemosensory cells) and intercellular pathways have evolved to detect and transmit information about the chemosensory environment of the animal. Although different organisms may employ slightly different mechanisms in chemosensory pathways, the general picture that has emerged from research with a limited number of albeit widely separated groups (particularly arthropods and vertebrates) is that the underlying principles that govern chemosensory systems are remarkably similar. However, very little attention has been paid to the earliest metazoans, the "first" animals to bear specialized sensory cells. Cnidarians (sea anemones, corals and jellyfish) represent some of the earliest metazoans, and they are the first extant organisms to possess a recognizable nervous system. Thus, they are ideal animals with which to examine the properties of early metazoan chemosensory systems and, in particular, to determine whether the common mechanisms of chemosensory function apply to all metazoans. This proposal seeks to examine chemosensory transduction in cnidarians, by studying a system that, in and of itself, is both fascinating and remarkable, the stinging cells of jellyfish. The sting cells or cnidocytes of jellyfish and other cnidarians discharge in response to near simultaneous applications of the chemical and mechanical stimuli that signal the presence of potential prey. However, this discharge is very tightly regulated by a variety of processes, including chemoreceptors and mechanoreceptors. This proposal will examine chemoreceptors associated with cnidocytes in the tentacles of two species, the Portugese Man-of-War (Physalia physalis) and sea nettle (Chrysaora quinquecirrha), two species that are, at the very least, serious nuisances for bathers and fishermen. The broad goals of this project are to understand the mechanisms used by those receptors to detect and transduce chemical stimuli, to convey that information to the cnidocytes, and identify and characterize the cellular events that information triggers in the cnidocytes, making them receptive to the subsequent mechanical stimuli that trigger discharge. As such, this project will obtain basic information about chemosensory systems in early organisms. The project also has very applied goals inasmuch as information about the pathways and mechanisms that regulate cnidocyte discharge may provide useful insights into ways to inhibit cnidocyte discharge. Such information could ultimately be used to develop ways to protect bathers and fishermen from the painful and sometimes dihabilitating stings these animals can produce. The project will provide training to at least one postdoctoral fellow, and to several undergraduates through the Whitney Laboratory's very active and successful Research Experience for Undergraduates Program. This program has an excellent record of including minorities, and at least one minority student is expected to be trained through this project.