Magnetoreceptive

Magnetoreceptive describes animals or tissues that can detect magnetic fields. Magnetoreception is the sensory modality that enables animals to sense Earth's geomagnetic field to determine direction, altitude, or geographic position. This ability has been reported in a variety of taxa, including birds, insects, fish, turtles, and some bacteria. In humans, evidence for functional magnetoreception is limited and remains controversial.

Two leading mechanisms are proposed. The magnetite-based mechanism posits biogenic magnetite crystals in sensory tissues act as compass needles, influencing nerve activity. In birds, proposed magnetoreceptors in the upper beak region have been studied, though evidence remains debated. The radical-pair mechanism involves cryptochrome proteins in the retina, where light-driven chemical reactions create spin-correlated radical pairs whose chemistry is influenced by the geomagnetic field, potentially guiding orientation.

Ecological roles include long-distance migration, orientation, and spatial mapping. Migratory birds repeatedly align routes with the Earth's field; sea turtles use magnetoreception during early orientation; certain fish and sharks may use magnetic cues for schooling and navigation. Bacteria such as magnetotactic species align along field lines to locate optimal habitats, a form of magnetotaxis rather than true magnetoreception in the animal sense.

Research and terminology: Magnetoreception is the overall sense; magnetoreceptive describes organisms or sensory cells capable of detecting magnetic fields. Magnetoreceptors can be magnetite-based or cryptochrome-based. Scientists employ behavioral assays, genetic and neural investigations, and electrophysiology to study these systems. Despite progress, the full mechanisms and prevalence across species are still actively investigated.