Magnetic Compass Orientation in Larval Iberian Green Frogs, Pelophylax Perezi


Francisco J. Diego-Rasilla, Departamento de Biología Animal, Universidad de Salamanca, Campus Miguel de Unamuno, Edificio de Farmacia 5a planta, 37007 Salamanca, Spain.


Experiments were carried out to investigate whether Iberian green frog tadpoles Pelophylax perezi (formerly Rana perezi) are able of using the geomagnetic field for y-axis orientation (i.e. orientation toward and away from shore). Tadpoles were trained outdoor for 5 d, in two different training configurations: (i) a training tank aligned along the magnetic north–south axis, with shore facing south, and (ii) a training tank aligned along the magnetic east–west axis, with shore located east, and similar to the shore–deep water axis (‘y-axis’) found in their home stream, which flows from south to north. After training, tadpoles were individually tested for magnetic orientation in a water-filled circular outdoor arena surrounded by a pair of orthogonally aligned cube-surface-coils used to alter the alignment of the earth's magnetic field. Tadpoles held in the east–west training tank oriented towards shore, indicating that they were able to distinguish between the shoreward and waterward direction along the y-axis. Tadpoles trained in the tank that was aligned along the north–south axis showed bimodal magnetic compass orientation along the shore–deep water magnetic axis. These findings provide evidence for the use of magnetic compass cues for y-axis orientation by P. perezi tadpoles.