Use of a light-dependent magnetic compass for y-axis orientation in European common frog (Rana temporaria) tadpoles
We provide evidence for the use of a magnetic compass for y-axis orientation (i.e., orientation along the shore-deep water axis) by tadpoles of the European common frog (Rana temporaria). Furthermore, our study provides evidence for a wavelength-dependent effect of light on magnetic compass orientation in amphibians. Tadpoles trained and then tested under full-spectrum light displayed magnetic compass orientation that coincided with the trained shore-deep water axes of their training tanks. Conversely, tadpoles trained under long-wavelength (≥500 nm) light and tested under full-spectrum light, and tadpoles trained under full-spectrum light and tested under long-wavelength (≥500 nm) light, exhibited a 90° shift in magnetic compass orientation relative to the trained y-axis direction. Our results are consistent with earlier studies showing that the observed 90° shift in the direction of magnetic compass orientation under long-wavelength (≥500 nm) light is due to a direct effect of light on the underlying magnetoreception mechanism. These findings also show that wavelength-dependent effects of light do not compromise the function of the magnetic compass under a wide range of natural lighting conditions, presumably due to a large asymmetry in the relatively sensitivity of antagonistic short- and long-wavelength inputs to the light-dependent magnetic compass.
KeywordsAnuran Magnetic compass Light-dependent magnetoreception Rana temporaria y-axis orientation
The Cantabria autonomous government (Dirección General de Montes y Conservación de la Naturaleza) granted the necessary permits for the study. We sincerely thank Marcos Diego-Gutiérrez for invaluable assistance during this study. Comments by Michael Painter improved the manuscript. J.P. was supported by a grant from the NSF (USA) IOS 07-48175. The experiments reported herein comply with the current laws of Spain. The authors declare that they have no conflict of interest.
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