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Light-Dependent Shift in Bullfrog Tadpole Magnetic Compass Orientation: Evidence for a Common Magnetoreception Mechanism in Anuran and Urodele Amphibians


Michael J. Freake, Department of Natural Sciences and Mathematics, Lee University, 1120 Ocoee St., Cleveland, TN 37311, USA. E-mail:


Previous studies have demonstrated the presence of a light-dependent magnetic compass in a urodele amphibian, the eastern red-spotted newt Notophthalmus viridescens, mediated by extraocular photoreceptors located in or near the pineal organ. Newts tested under long-wavelength (≥500 nm) light exhibited a 90° shift in the direction of orientation relative to newts tested under full spectrum (white) or short-wavelength light. Here we report that bullfrog tadpoles Rana catesbeiana (an anuran amphibian) exhibit a 90° shift in the direction of magnetic compass orientation under long-wavelength (≥500 nm) light similar to that observed in newts, suggesting that a common light-dependent mechanism mediates these responses. These findings suggest that a light-dependent magnetic compass may have been the ancestral state in this group of vertebrates.