Light-dependent shift in bullfrog tadpole magnetic compass orientation: Evidence for a common magnetoreception mechanism in anuran and urodele amphibians

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 (greater than or equal to500 nm) light exhibited a 90degrees 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 90degrees shift in the direction of magnetic compass orientation under long-wavelength (greater than or equal to500 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.