Weak Magnetic Field Effects on Pigmentation in Tadpoles

Magnetic fields (MFs) are abundant in biology, phenomena that become particularly intriguing when dealing with weak MFs. Classical explanations often fall short due to the energies associated with these weak MFs being considerably below thermal energies. Here, we investigated the effects of MFs < 1 mT on tadpoles. Our experiments demonstrated a notable increase in morphological pigmentation around the eye-cheek area in tadpoles subjected to a 0.5 mT magnetic field for 5 days, particularly noteworthy in embryos kept in a 12/12 L/D environment. We observed time-dependent effects, with detectable changes in response to a 0.25 mT magnetic field becoming apparent after 3 days of exposure. The magnetic field effects exhibited variation with changes in the strengths of the magnetic fields applied, indicating a nuanced relationship between field strength and biological response. Further exploration involved investigating the role of cryptochrome proteins, known for their potential involvement in MF effects. RT-PCR detected the expression of all three cryptochromes found in X. laevis (Cry1, Cry2, and Cry4) in both the eye and a melanophore cell line (MEX cells). Using an antibody recognizing Cry1, we identified the presence of the protein in melanophores in the skin and photoreceptors in the eye. MFs were found to increase the melanization of pigment cells in vitro, suggesting a direct impact on cellular processes. Based on our observations, we modelled the experimental data with a Radical Pair Mechanism (RPM) model involving CRY. We examined the FAD-Trp and FADH-superoxide pairs. Notably, our theoretical model, which includes an amplification pathway, successfully reproduces our experimental results, favouring FADH-superoxide pairs. This work contributes to the growing body of evidence supporting the involvement of weak magnetic fields in biological processes and underscores the importance of the RPM as a key explanatory framework.