The trigeminal cranial nerve of rainbow trout helps them detect magnetic fields by containing magnetosensitive nerve fibers.

“In 1997, the first known magnetoreceptors — directly linking magnetite to neural connections and activity — were found in vertebrates. A team of zoologists from Auckland University, led by Dr. Michael Walker, had been studying this mysterious sense in trout, and knew that a region of its skull contained magnetite.

“Recording neural activity from that region, they discovered that a specific subgroup of nerve fibers within a branch of the trigeminal cranial nerve called the ros V nerve fired in response to changes in the surrounding magnetic field. They also found magnetite in a tissue layer directly beneath the trout’s olfactory (smell) organs. When they injected a colored dye into the ros V nerve’s newly exposed magnetosensitive fibers, the dye revealed that the fibers terminated and ramified all around the magnetite-containing cells within the trout’s olfactory tissue.” (Shuker 2001:46)

Last Updated August 18, 2016