Magnetoreception by animals remains a puzzling issue in neuroscience. While behavioral experiments have demonstrated that different kinds of animals apparently can detect the earth's magnetic field and use it for orientation or migration. The mechanisms of how the nervous system might detect this property are largely unknown. Sea slugs are marine invertebrates related to snails, with a relatively simple nervous system, and these animals provide an excellent model system for neurobiology because there are some particular nerve cells in the brain that are consistently identifiable across individuals of a species. Recently, one kind of sea slug has been found to have some nerve cells in its brain that respond to changing the orientation of earth-strength magnetic fields. These neurons are the first identifiable cells in any animal that are known to respond to magnetic stimuli. This projeat uses electrophysiology and anatomy to clarify the function and connections of these neurons, to use them as a starting point to launch a careful search for the cells or structures that detect magnetic fields. Results from this work will provide a new understanding of a mysterious but potentially very important sense. The work will help explain how migratory animals may be be able to navigate long distances, and so have an impact beyond neuroscience to behavioral sciences, ecology, and environmental sciences.
