This is a project to study some of the physical factors involved in sensing of chemicals. The basic issue being approached is how the chemicals that are being sensed are transported to the receptor organs, and how the processes are modified by evolutionary specializations in morphology and behavior. The animal model of chemical sensing that is used is the detection of amino acids by lobster olfactory receptors. In these animals the amino acids, which are feeding stimuli, diffuse to the receptors. In doing so, they finally must diffuse through very thin layers of fluid adjacent to the organs themselves. Different chemoreceptor organs, even in the same animal, can have dramatically different morphology that can result in different diffusion layers. In addition, the animal's behaviors in sampling the environment (flicking and sniffing, for example), affect the boundary layer and also help to minimize the confounding effects of turbulence in the environment. The project will include testing a computational model of receptor organ filtering by measuring and manipulating diffusion layers in different chemoreceptor organs and measuring the time courses of responses in the cells in the living animals. Thus, it will result in an understanding of the structure and function of diffusion layers and of their contribution to analysis of chemical signals. The principles of filtering being studied here in the lobster are important components of all chemical sensing systems. They are little studied and poorly understood, and the conclusions drawn in this study should have wide generalizability to other systems as we..
