1. Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA

Correspondence to: Steven M. Reppert¹ Correspondence and requests for materials should be addressed to S.M.R. (Email: steven.reppert@umassmed.edu).

Abstract

Although many animals use the Earth's magnetic field for orientation and navigation^{1, 2}, the precise biophysical mechanisms underlying magnetic sensing have been elusive. One theoretical model proposes that geomagnetic fields are perceived by chemical reactions involving specialized photoreceptors³. However, the specific photoreceptor involved in such magnetoreception has not been demonstrated conclusively in any animal. Here we show that the ultraviolet-A/blue-light photoreceptor cryptochrome (Cry) is necessary for light-dependent magnetosensitive responses in Drosophila melanogaster. In a binary-choice behavioural assay for magnetosensitivity, wild-type flies show significant naive and trained responses to a magnetic field under full-spectrum light (300–700 nm) but do not respond to the field when wavelengths in the Cry-sensitive, ultraviolet-A/blue-light part of the spectrum (<420 nm) are blocked. Notably, Cry-deficient cry⁰ and cry^b flies do not show either naive or trained responses to a magnetic field under full-spectrum light. Moreover, Cry-dependent magnetosensitivity does not require a functioning circadian clock. Our work provides, to our knowledge, the first genetic evidence for a Cry-based magnetosensitive system in any animal.

1. Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA

Correspondence to: Steven M. Reppert¹ Correspondence and requests for materials should be addressed to S.M.R. (Email: steven.reppert@umassmed.edu).

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