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How desert ants use Earth's magnetic field for navigation 

In the vast and often harsh landscapes of the desert, where survival hinges on the ability to navigate effectively, ants of the genus Cataglyphis exhibit a remarkable feat of orientation. 

These desert ants – though diminutive in size and possessing brains with less than one million neurons – have been found to use the Earth’s magnetic field for navigation. 

Processing magnetic information 

The remarkable discovery, which was initially made by researchers from the University of Würzburg (JMU), challenged previous understandings of animal navigation and prompted further investigation into the underlying mechanisms.

The latest study provides brand new insights into how desert ants process magnetic information. The researchers have discovered that the ants’ internal compass, known as the central complex, is a key site for processing Earth’s magnetic signals. These signals are also processed in “mushroom bodies” that are responsible for learning and memory in the ant’s brain.

Learning walks

Dr. Pauline Fleischmann elaborated on the ants’ preparatory behaviors, noting that before venturing out for the first time, the ants perform learning walks to calibrate their navigation systems. “Before an ant leaves its underground nest for the first time and goes in search of food, it has to calibrate its navigation system.”

These walks involve intricate movements and orientations that align them with the magnetic field, even when the nest entrance – a mere hole in the ground – is out of sight. The team’s field studies in southern Greece, where these ants are native, have demonstrated that these orientation behaviors are indeed influenced by Earth’s magnetic field.

Focus of the study 

The experts analyzed young workers that had not yet undertaken any learning walks. The desert ants were observed in experiments that were precisely planned out. 

The ants were sometimes allowed to venture out under natural conditions, and other times they were allowed to venture out in a manipulated magnetic field that displayed chaotic directions or did not allow horizontal orientation. 

With this faulty directional information, it was not suitable as a reliable reference system for the ants’ behavior to look back to the nest entrance during the learning walks, noted the researchers.

Spatial memory formation 

“Our neuroanatomical brain analyses show that ants exposed to an altered magnetic field have a smaller volume and fewer synaptic complexes in an area of the brain responsible for the integration of visual information and learning, the so-called mushroom body,” explained the study authors.

This contrasted sharply with ants that experienced natural magnetic conditions, whose sensory experiences led to an increase in synaptic connections in these brain regions. The results demonstrate the importance of magnetic information for spatial memory formation.

Broader implications 

According to the experts, the research extends beyond the calibration of the ants’ compass. It sheds light on the broader implications of multisensory stimuli on neuronal plasticity and navigation.

Going forward, the team plans to investigate which sensory organ receives the magnetic information and via which sensory pathways it is transmitted and processed. Ultimately, the desert ant may be used as a model organism for studying the neuronal underpinnings of navigation.

The study is published in the journal Proceedings of the National Academy of Sciences.

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