Magnetoreception and Magnetotactic Orientation

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Behavioral studies carried out over the last 20 years indicate that many, perhaps most, types of animals detect the earth's magnetic field and use this source of directional information to guide their movements. Remarkably, however, among higher animals and, in particular, land-dwelling vertebrates, the way in which the magnetic field is detected has not been determined. Recent studies of the Eastern newt have shown that this salamander is an especially good subject for studying magnetic- field sensitivity because it exhibits much stronger responses to earth-strength magnetic fields in the laboratory than have been observed for other vertebrates. Furthermore, the Eastern newt exhibits two types of magnetic responses with different properties, suggesting that two different magnetoreception systems may be involved. Dr. Phillips will carry out behavioral experiments designed to elucidate the sensory mechanism(s) responsible for detection of the earth's magnetic field. Specifically, these experiments will test the hypothesis that the Eastern newt has two different magnetoreception systems: one system utilizing small particles of the mineral magnetite that act like tiny compass needles and a second system that relies on specialized visual receptors that, in effect, "see" the magnetic field. Determining how vertebrates detect the earth's magnetic field and, in particular, whether the visual system plays a role in this sensory capability is of considerable importance to our understanding of the detection and processing of sensory information by vertebrates, including man.