Migratory songbirds have the remarkable ability to extract directional information from the Earth’s magnetic field^1,2. The exact mechanism of this light-dependent magnetic compass sense, however, is not fully understood. The most promising hypothesis focuses on the quantum spin dynamics of transient radical pairs formed in cryptochrome proteins in the retina^3,4,5. Frustratingly, much of the supporting evidence for this theory is circumstantial, largely because of the extreme challenges posed by genetic modification of wild birds. Drosophila has therefore been recruited as a model organism, and several influential reports of cryptochrome-mediated magnetic field effects on fly behaviour have been widely interpreted as support for a radical pair-based mechanism in birds^{6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23}. Here we report the results of an extensive study testing magnetic field effects on 97,658 flies moving in a two-arm maze and on 10,960 flies performing the spontaneous escape behaviour known as negative geotaxis. Under meticulously controlled conditions and with vast sample sizes, we have been unable to find evidence for magnetically sensitive behaviour in Drosophila. Moreover, after reassessment of the statistical approaches and sample sizes used in the studies that we tried to replicate, we suggest that many—if not all—of the original results were false positives. Our findings therefore cast considerable doubt on the existence of magnetic sensing in Drosophila and thus strongly suggest that night-migratory songbirds remain the organism of choice for elucidating the mechanism of light-dependent magnetoreception.

迁徙鸣禽具有从地球磁场中提取方向信息的非凡能力^1,2 。然而，这种依赖于光的磁罗盘感应的确切机制尚不完全清楚。最有希望的假设集中在视网膜隐花色素蛋白中形成的瞬时自由基对的量子自旋动力学^3,4,5 。令人沮丧的是，这一理论的许多支持证据都是间接的，很大程度上是因为野生鸟类的基因改造带来了极端的挑战。因此，果蝇被选为模式生物，并且关于隐花色素介导的磁场对苍蝇行为的影响的几项有影响力的报告已被广泛解释为对鸟类中基于配对的激进机制的支持^{6,7,8,9,10,11 ,12,13,14,15,16,17,18,19,20,21,22,23} 。在此，我们报告了一项广泛研究的结果，该研究测试了磁场对 97,658 只在两臂迷宫中移动的果蝇以及 10,960 只执行自发逃逸行为（称为负趋地性）的果蝇的影响。在严格控制的条件下和大量的样本量下，我们无法找到果蝇磁敏感行为的证据。此外，在重新评估我们试图复制的研究中使用的统计方法和样本量后，我们认为许多（如果不是全部）原始结果都是误报。因此，我们的研究结果对果蝇是否存在磁感应产生了相当大的怀疑，因此强烈表明夜间迁徙鸣禽仍然是阐明光依赖性磁感受机制的首选生物体。