A reproducible model for magnetosensitivity: earthworms in transparent soil reduce their cumulative movement in an extremely weak magnetic field.

The magnetic sense remains one of the mysteries of sensory biology. Despite 50 years of extensive research, science seems to be at a standstill. One of the major factors contributing to this scientific stasis is the lack of simple, reproducible model systems. Here, we examine magnetoreception in earthworms held in transparent soil. Using video recordings and machine learning-based analysis, we show that earthworms move significantly less when held in a near-zero magnetic field (nZMF). This effect of nZMF on earthworm activity was highly reproducible and significant through all trials. Furthermore, under some circumstances the earthworms showed significant group magnetic directionality; however, this result was not reproducible. By using earthworms in transparent soil and manipulating the magnetic field, we created a robust protocol that facilitates examination of magnetoreception in a simple organism. This may serve as a crucial springboard in the ongoing quest to unravel this mysterious sense.