Photoreceptors in avian magnetoreception

Abstract

The geomagnetic field is an important source of directional information and a physiological magnetic compass has been demonstrated in numerous species of migratory birds as well as other animals ([Wiltschko and Wiltschko 1995a]). Recently, a growing body of behavioral evidence indicates that the avian magnetic compass involves blue-green photoreceptors that can undergo redox chemistry (radical-pair reactions). We will review the current knowledge of the wavelength dependence of magnetic compass responses. We present the current model that the magnetic sensitivity is based on the influence of magnetic fields on singlet-triplet transitions in photoreceptors and review recent evidence supporting such a chemical sensing mechanism. Having identified the mechanism of the magnetic compass, the field of magnetoreception now calls for genetic and molecular approaches to identify the molecular basis of photoreceptor-based magnetoreception. We discuss potential receptor candidates and implications on plant morphogenesis.