To study the magnetic orientation in hatchling loggerhead sea turtles.
Loggerhead sea turtles derive both directional and positional information from the Earth's magnetic field, but the mechanism underlying magnetic field detection has not been determined. One hypothesis is that crystals of biogenic, single-domain magnetite provide the physical basis of the magnetic sense. To determine if magnetite is involved in sea turtle magnetoreception, hatchling loggerheads were exposed to pulsed magnetic fields capable of altering the magnetic dipole moment of biogenic magnetite crystals.
|Pulse width||4 ms|
|magnetic flux density||40 mT||unspecified||measured||-||-|
Control and exposed groups of turtles oriented toward a light source, implying that the pulsed fields did not disrupt the motivation to swim or the ability to maintain a consistent heading. However, when swimming in darkness under conditions in which turtles normally orient magnetically, control animals oriented significantly toward the offshore migratory direction while those that were exposed to the magnetic pulses did not.
These data are consistent with the hypothesis that at least part of the sea turtle magnetoreception system is based on magnetite. In principle, a magnetite-based magnetoreception system might be involved in detecting positional information, directional information, or both.