Nearly blind, burrowing underground, Ansell’s African mole rats can sense magnetic fields with their eyes, according to a study.
Native to Zambia, the animals have eyes that measure only 1.5mm in diameter, live in elaborate underground tunnel systems up to 1.7 miles (2.8 km) long, and feed on tubers and plant roots.
Typically, animals show an innate preference for building nests in the southeastern sector of a circular arena, while other mole rats prefer different directions.
To determine how they orient themselves, researchers from the University of Duisburg-Essen in Germany surgically removed the eyes of a group of moles.
Initially, they tested six mole-rat pairs, finding that they preferred the southeast for nest building before surgery, but after surgery, activity was random. These results suggested that the rodents’ magnetic senses were impaired after surgery, but other factors, including topography, were not excluded.
A second experiment was then conducted comparing 10 mole rats with surgically removed eyes with 10 in a control group. The researchers tested four alignments of the magnetic field: those in the control group went southeast, while the other group was not partial in that direction.
Crucially, the post-surgical mole rats showed no other behavioral changes, the scientists wrote in the Journal of the Royal Society Interface.
Magnetoreception, the ability to sense magnetic fields, has been demonstrated in a number of animals, but the structure and location of magnetoreceptor cells have not been clear.
Previous research has also indicated that this rat-mole’s eyes are indispensable for detecting magnetic signals. In one experiment, when a local anesthetic was applied to the cornea of the eye of mole rats, they lost the ability to orient themselves. This approach has some drawbacks, said lead author Kai Caspar, as the drug could penetrate the blood-brain barrier and trigger a cascade effect on the nervous system.
Does the new study mean that Ansell’s mole rats kept their eyes – in contrast to their largely blind underground counterparts – due to these magnetic receptors?
The receptor in question didn’t appear to be placed in any spatial order – any organ could do the trick, Caspar said, noting that blind mole mice retain their ability to detect magnetic signals. “We still don’t know why Ansell moles keep their eyes. This magnetoreception seems not to be the answer “.