Dr. Phillips will use behavioral techniques to examine the detection and use of the earth's magnetic field by the eastern newt (Notophthalmus viridescens). Previous work has shown that the magnetic compass used by newts for shoreward orientation is influenced by the wavelength of light. Measurements of the wavelength-dependence of magnetic compass orientation will be extended into the near-ultraviolet to better characterize the visual inputs that contribute to the magnetic compass. In addition, the wavelength of light reaching the pineal organ and eyes will be selectively altered to find out if the light- dependent magnetic compass is located in one of these two photoreceptive organs. To investigate the involvement of the magnetic field in homing and, more specifically, in the "map" or geographic-position sense that is required for homing, experiments will be carried out to examine the effects of varying the wavelength of light and of manipulating specific components of the magnetic field (i.e., the dip angle and total intensity) on homing orientation. This research will contribute to a better understanding of the function of the pineal and of the processing of sensory information by the brain of vertebrates. In addition, the information gained from this research will help to characterize the extent to which the visual system of amphibians has become specialized to perform specific sensory functions (i.e., detection of the earth's magnetic field). A more complete understanding of these specialized sensory functions will make it possible to determine when the amphibian visual system can serve as an appropriate model system for studying visual processes that occur in other vertebrates, including humans. Finally, investigation of the strategies used by amphibians to orient during long-distance movement will contribute to a better understanding of how the brain of vertebrates processes spatial information.
