Magnetoreception: An exciting field of challenges, hopes, wishes and beyond

Abstract

The ability of animals to sense the geomagnetic field and perceive guidance cues for orientation and navigation has been a subject of lively debate since the beginning. A wealth of behavioral evidences has been accumulated and several sophisticated theoretical models including electromagnetic induction, ferrimagnetism, radical pairs model based on cryptochrome and biocompass model based on MagR and MagR/Cry protein complex have been proposed. However, the mechanism of magnetoreception remains largely unknown up to date, and thus exciting. How do migratory organisms find their way has been listed by Science as one of 125 most compelling scientific questions that cannot currently be answered, but are on the horizon. Here in this historical review, we firstly focused on examining the magnetoreception research throughout the last two centuries emerged in the literatures. We then reviewed the four major hypotheses behind this scientific mystery, and highlighted pros and cons of each hypothesis. We also discussed that if it was possible that a universal mechanism can be applied to explain all questions in animal magnetoreception, from the perspective of biodiversity and evolution. One of the heated controversies in magnetoreception is that can human navigate by sensing the geomagnetic field? We explored the research history of human magnetoreception in this review. The question can be traced back to 1873 when Charles Darwin wrote a letter to Nature , arguing that animals including human have the “instinct” to navigate. Then after almost 100 years, Robin Baker claimed to find a human compass sense of magnetic field in “Manchester Experiments” in Science in 1980, but the replication efforts all failed for more than 30 years by other groups. This controversy topic was then re-visited in 2019 and two groups published results suggesting many humans are able to unconsciously detect changes in Earth-strength magnetic fields, which raised more questions in this field. Putting the research history into perspective, we then discussed the unique features of biological magnetoreception, the approaches currently used in this field, the challenges we were facing and the possible solutions. We listed the contradictions in four current major models to explain the mechanism of biological magnetic sensing, and why the controversies could happen. We proposed that the pattern to perceive magnetic field should be regarded as “massive event”, since all molecules/receptors would respond to the changes of external magnetic field spontaneously, which was fundamentally different than the “single event” pattern when a chemical ligand binding to its receptor. We argue that a better understanding of the differences between magnetoreception and other sensory systems would help us to resolve this scientific mystery in the future.