Animal

Near-blind Ansell's mole-rats detect magnetic cues with eyes, study shows


Near-blind, underground-burrowing, African Ansell’s mole-rats can sense magnetic fields with their eyes, a study has found.

Native to Zambia, the animals have eyes that span just 1.5mm in diameter, live in elaborate underground tunnel systems of up to 1.7 miles (2.8km) long and feed on plant tubers and roots.

The Ansell’s mole-rat’s eyes are barely functional. They cannot see colour or form sharp images, and their main function is to differentiate between light and dark.

Typically, the animals display an innate preference to construct nests in the south-east sector of a circular arena, while other mole-rats prefer different directions.

To establish how they orientate themselves researchers at the University of Duisburg-Essen in Germany surgically removed the eyes of a group of mole-rats.

Initially, they tested six mole-rat pairs, finding that before surgery they preferred the south-east for nest building, but after surgery the activity was random. These results suggested the rodents’ magnetic senses were impaired post-surgery, but other factors including topography were not ruled out.

A second experiment was then conducted comparing 10 mole-rats with surgically removed eyes with 10 in a control-group. The researchers tried four magnetic field alignments – those in the control group went south-east, while the other group was not partial to that direction.

Crucially, post-surgery mole-rats did not display any other behavioural changes, the scientists wrote in the Journal of the Royal Society Interface.

Magnetoreception, the ability to sense magnetic fields, has been demonstrated in a range of animals, but the structure and location of the magnetoreceptor cells has been unclear.

Previous research has also indicated that this mole-rats’ eyes are imperative to detecting magnetic cues. In one experiment when a local anaesthetic was applied to the cornea of the mole-rats’ eye they lost their ability to orient. This approach had some drawbacks, said the author of the new study, Kai Caspar, as the drug could penetrate the blood-brain barrier and trigger a cascading effect on the nervous system.

Does the new study mean Ansell’s mole-rats have retained their eyes – in contrast to their largely blind subterranean counterparts – because of these magnetic receptors?

The receptor in question did not appear to be positioned in a spatial order – any organ could do the trick, Caspar said, noting that blind mole-rats retain their ability to detect magnetic cues. “We still do not know why Ansell mole-rats retain their eyes. This magnetoreception appears to be not the answer.”



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