Each year, the Arctic Tern migrates nearly twenty-thousand miles from the Arctic Circle to the Antarctic Circle and back again. The manner in which these remarkable creatures navigate along their way has long been a subject of contention among scientists. A recent study, however, suggests that certain organisms -including those of the non-avian variety- are actually able to visualize the magnetic field and move according to it.
In general, three theories on the matter have been proposed. One suggests the presence of biologically created magnetite crystals, which respond directly to the core of the earth. Another postulates that electromagnetic induction is responsible; perhaps an intracellular mechanism converts reception of the electric field into magnetic sensitivity. The final, however, appears to be backed by a large volume of research.
Known generally as the “quantum biological theory of magnetoreception,” this rather strange hypothesis has accompanied the rise of an entirely new field of natural science: quantum biology. Sitting at the intersection of physics, chemistry, and biology, quantum biology is a small but rapidly growing subdivision of academia that applies quantum mechanics to chemical and biological processes. In the context of magnetoreception (as any sensory perception of the geomagnetic field is referred to), quantum biologists believe that a light-sensitive protein found in the retina may be responsible. This photosensitive protein, a part of the flavoprotein group called “cryptochromes,” releases two molecules when hit at a specific angle with light. These molecules constitute a complex process dubbed the “radical pair mechanism”.
In simple terms, a radical is an atom or molecule with an odd number of electrons. Radicals are created whenever some form of energy (i.e. the light hitting the retina) breaks apart the two electrons holding the molecules together, resulting in two semi-magnetic particles. Each radical is essentially trying to return to its full state and reconnect with a molecule, whether that be the molecule it was previously connected to or another molecule in the area. This selection is not random: in fact, it is heavily influenced by the direction in which the Earth’s magnetic field acts on the produced pairs. Whichever molecule it ultimately returns to results in a chemical reaction of a bond being formed. As is customary with all chemical reactions, the formation of a bond releases energy. However, the amount of energy released by each molecular reaction varies: reconnecting with the molecule it was previously bonded to might release a certain amount of energy while bonding with an entirely new molecule might release a lot more. This energy release takes the form of a signal that is thought to supplement the normal optical broadcast via the optic nerve to a region of the brain labelled “Cluster N”. It is then analyzed and forms an overlay of the normal vision. Overall, the process is thought to result in a comprehensive view of the bumps and waves of the geomagnetic field dependent on direction.
Organisms supposedly recognize the aforementioned variations in their sight and select their route accordingly. Although the process remains highly hypothetical, in vivo laboratory action on European Robins has shown promise in the implication of cryptochrome and radical pairs in magnetoreception. Studying these systems in animals provides a gateway to more complete comprehension of both our internal and external environments. Considering humans also possess variations of cryptochrome in the retina, it is entirely possible that the future could include readily available optical enhancements to view the magnetic field.
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