Certain mammals are able to detect magnetic fields, but where the sense originates from has long remained elusive. Now, the organ that houses magnetic sensors in mole rats has been identified.
Kai Caspar at the University of Duisburg-Essen in Germany and his colleagues have found that the Ansell’s mole rat (Fukomys anselli) uses its eyes for magnetoreception.
This species of mole rat, known for digging long, subterranean tunnels, has poor eyesight and tiny – but structurally intact – eyes. “They do not orient by vision,” says Caspar. “Vision is more or less completely unimportant for them.”
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Previous research had pointed to the eyes as being the potential location of magnetoreceptors in these mammals. In birds, the eye is also associated with magnetic sensing.
To find out if a similar magnetoreceptor was at work here, the team studied the behaviour of 40 Ansell’s mole rats, 22 of which had their eyes removed.
They found that the animals without eyes didn’t change their foraging or socialising behaviour. However, there was a change in the orientation of nests that the mole rats built.
Many rodents, including several mole rat species and the wood mouse, consistently build nests in particular orientations. The reasons why they do so are unclear, says Caspar.
The researchers placed the Ansell’s mole rats in a circular arena in which magnetic fields could be used to artificially change the direction of magnetic north. They found that the mole rats with intact eyes always built their nests in the magnetic south-eastern quadrant of the arena.
The animals without eyes built their nests in random orientations, suggesting that their magnetic sense had been disrupted.
This is the first time that a specific organ housing magnetoreceptors has been identified in mammals. The specific magnetic receptors in the Ansell’s mole rat eye haven’t yet been identified, but the researchers believe they may contain magnetite, a magnetic iron ore.
Journal of the Royal Society Interface
