DITTMAN, A.H.: Sensory systems and neural mechanisms involved in salmon homing

Pacific salmon (Oncorhynchus spp.) are well known for their long distance homing migrations from oceanic feeding grounds back to their river of origin to spawn. During these migrations, salmon travel through a variety of habitats (e.g., oceans, estuaries, lakes, rivers) and therefore may utilize a number of sensory modalities for navigation. I will review the sensory capabilities and neural mechanisms that may be involved in all aspects of salmon homing but emphasize the final freshwater phase of the migration governed by olfactory discrimination of homestream water. Prior to their seaward migration, juvenile salmon learn (imprint to) odors associated with their natal site and later use these odor memories for homing. Experiments using single artificial odorants have indicated that the peripheral olfactory system is sensitized to homestream odors during imprinting and that some components of the homestream memory may be encoded at the level of olfactory receptor neurons (ORN). I will describe recent studies to explore the molecular basis of ORN sensitization during imprinting and discuss how these cellular changes may influence orientation and navigation capabilities during the homing migration.