Study type: Medical/biological study (experimental study)

Disruption of magnetic orientation in hatchling loggerhead sea turtles by pulsed magnetic fields. med./bio.

Published in: J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2005; 191 (5): 475-480

Aim of study (acc. to editor)

To study the magnetic orientation in hatchling loggerhead sea turtles.

Background/further details

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.

Endpoint

Exposure

Exposure Parameters
Exposure 1:
Modulation type: pulsed
Exposure duration: five pulses

Exposure 1

Main characteristics
Type
Waveform
Exposure duration five pulses
Modulation
Modulation type pulsed
Pulse width 4 ms
Exposure setup
Exposure source
Setup solenoid arranged so that it generated a magnetic field with its polarity reversed relative to the earth`s field; animals placed in the solenoid
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 40 mT unspecified measured - -

Reference articles

  • Beason R et al. (1995): Behavioural evidence for the use of magnetic material in magnetoreception by a migratory bird.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

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.

Study character:

Study funded by

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