June 30, 2025

Saloni Roy

9th Grade

Holton-Arms School 

A manta ray skims above the ocean floor, its huge fins dusting the sand below. Nearby, a shark cuts through the water, searching for prey. A tiny honey bee lands on a soft flower to the song of a robin. And miles away in the bustle of the city, a pigeon pecks for food. Despite the dramatic differences between these animals, they all have one thing in common: a keen sense of direction, guided by the Earth’s magnetic fields.

Magnetoreception, or the ability to sense magnetic fields, was thought impossible for years. Research on the subject was difficult due to the elusive issue of sensors. For one thing, the sensors would not need to be external; magnetic fields can pass through the body uninterrupted. These sensors could be spread out throughout an organism’s body without specific structures devoted to them. Finally, after years of research, trials, and doubt, scientists discovered three key mechanisms.

The first of the three is chemical magnetoreception. When experimentalist Albert Weller was watching one of his pet reactions, he noticed an enigma within it. His employee and fellow scientist, Klaus Schulten, soon found that it was caused by magnetic fields and began to develop the radical pair hypothesis.

The mechanism begins when one molecule transfers an electron to another. This leaves both molecules with an unpaired electron–an electron that is alone in its shell. Eventually, the electron will backtransfer, returning to its original molecule. But in the time between the original transfer and the backtransfer, electrons’ axes of rotation undergo a process known as precession. 

Precession occurs when the axes of rotation change in a way similar to the slowing of a spinning top. In some cases, when precession rates vary enough, they can change the original spin states of the electrons and chemically alter the donor molecule.

But how does this affect magnetoreception? Well, precession is altered by magnetic fields. So, if the molecules experience different magnetic fields, the precession rates would differ as well, causing a chemical change that animals could detect. Cryptochromes, found in several kinds of magnetosensitive birds and bacteria, are proteins where this reaction occurs, making this mechanism very likely.

Animals such as sharks and rays claim dominion over the second theory of magnetoreception. Known as elasmobranchs, these fish all possess conductive bodies and electrosensitive organs called ampullae of Lorenzi. Combined with their habitat in the oceans, these features make elasmobranchs perfectly suited to use electromagnetic induction.

Electromagnetic induction is defined as a current created due to a changing magnetic field. When Michael Faraday, who discovered electromagnetic induction, coiled a conductive wire around a bar magnet, he discovered that moving the bar affected the voltage. The same principle applies to elasmobranchs. When their conductive bodies move through the water, the Earth’s magnetic fields create a weak current that flows through the fish and water. As the animal moves, the magnetic field, relative to the animal, changes. This, in turn, causes the elasmobranch to experience a slight shift in voltage, detected by their hypersensitive ampullae of Lorenzi.  

But electromagnetic induction cannot function without electroreceptors, or in a non-conductive medium like air. Here, the third theory comes into play.

The key to this final mechanism is the mineral magnetite. Magnetite (Fe3O4) is a natural magnet, found in several different species: salmon, sea turtles, birds, honey bees, and several types of bacteria. Since magnetite naturally spins to align with the Earth’s magnetic field, several kinds of bacteria use it to do the same. With this ability, they can differentiate between up and down and find deeper waters. In larger organisms, magnetite would be a touch too small to rotate the entire animal (some crystals with a diameter of about 50 nanometers). Instead, it would interact with other sensors to provide information. For example, in trout, magnetite is linked with a nerve that reacts to magnetic stimuli.

The ability of magnetoreception and the mechanisms behind it open new doors in the scientific community. While the discovery of chemical magnetoreception, electromagnetic induction, and magnetite answers countless questions, they also raise new ones. Cryptochromes, the same proteins that aid magnetoreception in birds, are also present in humans. What does this discovery mean? Can magnetic fields cause sickness in humans? Could an absence of the Earth’s magnetic fields have similar effects? Yet conversely, magnetic fields may be able to serve as a kind of medicine. According to the studies of Margaret Ahmad, Research Director for Sorbonne University’s National Center for Science Research, some magnetic fields can induce molecules with the potential to treat injuries. 

These, and innumerable other ideas, questions, and theories, remain unresolved. Yet, one thing is for certain: as exploration of magnetoreception continues, scientists will continue to look towards the animal kingdom. From the smallest bacteria to the largest of rays, these fascinating creatures hold the keys to so many natural mysteries and the potential for infinite discoveries. It is crucial that we protect the animals sharing our planet. Without them, who knows how many senses we may never even discover?