Magnetoreception

Magnetoreception is the biological ability to detect magnetic fields, enabling orientation and navigation in animals. It has been documented in a variety of taxa, including bacteria, insects, fishes, birds, reptiles, and some mammals, and is an area of active research with ongoing questions about its neural pathways and integration with other senses.

There are two leading categories of magnetoreception. The radical-pair mechanism is light-dependent and is thought to operate in photoreceptor cells, particularly in the retina. In this mechanism, magnetic fields influence the spin dynamics of short-lived radical pairs formed during chemical reactions in proteins such as cryptochromes. The resulting changes in signaling are proposed to provide directional information, especially under blue-green light, and support a compass sense used for long-distance orientation in birds and possibly other species.

The magnetite-based mechanism involves biogenic magnetic iron oxide (magnetite) crystals that can physically align with the Earth's field and produce detectable forces on cellular or neural structures. This mechanism has strong experimental support in magnetotactic bacteria and is suggested in some studies of birds and other animals, where magnetite-containing cells in sensory tissues may interface with nerves to relay magnetic information.

In many species, magnetoreception interacts with other navigational cues such as the position of the sun, stellar patterns, wind, and olfactory information. While substantial progress has been made, the exact anatomical locations, neural circuits, and relative contributions of these mechanisms can vary across taxa, and in humans the existence and functionality of magnetoreception remain areas of debate.