Original title: Magnetosensitivity of amphibian morphological pigmentation is light- and eye-dependent and consistent with the radical pair mechanism
Hadi Zadeh-Haghighi, Gabriel E. Bertolesi, Sarah McFarlane, Christoph Simon · July 2026
Weak magnetic fields can alter living things, but scientists do not fully understand how. Researchers tested this by exposing Xenopus laevis tadpoles to weak magnetic fields. They wanted to see if the fields would change the animals' physical pigmentation, meaning the dark pigment cells around their eyes, called perioptic melanophores. The process relies on light and the animals' eyes to detect the field. Inside the cells, magnetic fields alter quantum spin states in pairs of molecules, known as the radical pair mechanism. The team found that weak magnetic fields directly changed the number of these pigment cells. The effect shifted as the field strength changed, matching predictions from a radical pair model. It mirrors how migratory birds may sense magnetic directions.
You are mixing two paints to get a specific shade. Normally the shade depends only on how much of each you use. But if a nearby magnet caused the paint molecules to rearrange, the shade would change with the magnet's strength. Here, the tadpole's pigment cells are like that paint mix: magnetic fields alter a chemical reaction inside them, causing more or fewer cells to form, and only if light is present.
This gives scientists a new way to study how living things sense magnetism, a process that helps birds navigate and might affect human biology. The tadpole's pigment cells change visibly, making the effect easy to measure. It could reveal how quantum effects drive biological decisions.
The study only shows that the results match the radical pair model, not that the model is correct. It examined only one type of pigment cell in one species of tadpole. The requirement for light and eyes suggests the effect is not universal across tissues. The biological steps between the magnetic field and changes in cell number remain unknown.
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Magnetosensitivity of amphibian morphological pigmentation is light- and eye-dependent and consistent with the radical pair mechanism — Hadi Zadeh-Haghighi, Gabriel E. Bertolesi, Sarah McFarlane et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.