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Headline: Secret of pigeons' homing instincts revealed - magnetic cells in the liver
Caption: **VIDEO AVAILABLE: CONTACT INFO@COVERMG.COM TO RECEIVE** BY MARK WORGAN The secret of how pigeons can find their way home over hundreds of miles has been revealed - magnetic cells found in their liver. A study published in Science suggests that specialised cells in the liver of pigeons can sense the Earth’s magnetic field, effectively giving the birds an internal compass. The cells, known as “macrophages”, are immune cells responsible for breaking down old red blood cells. In doing so, they accumulate iron, which researchers say may give them quantum properties allowing them to respond to magnetic fields. The study reports that without these cells intact, pigeons lose their ability to navigate home. “We didn’t expect immune cells to act like sensors for magnetic fields at all. Our results reveal a previously unknown mechanism for magnetic perception in animals,” says Prof. Christian Kurts, Director at the Institute of Molecular Medicine and Experimental Immunology at the University Hospital Bonn, and one of the study’s co-senior authors. “What looks like a ‘gut feeling’ in bird navigation may actually have a physical basis,” adds Prof. Martin Wikelski, Director at the Max Planck Institute of Animal Behavior and the other co-senior author of the study. For decades, scientists have known that migratory birds and homing pigeons use the Earth’s magnetic field as part of their navigation system. However, precisely how they detect it has remained one of biology’s unsolved questions. Competing theories have suggested birds might “see” magnetic fields via light-sensitive molecules in the eye or detect them using tiny magnetic particles in the beak, but neither has been conclusively proven. The new research proposes a different mechanism, combining laboratory work and behavioural experiments carried out by an international team of immunologists, physicists and ornithologists. To identify where magnetic sensitivity might originate, researchers screened multiple pigeon organs using techniques including “vibrating sample magnetometry” and “magnetic cell separation”. They examined the eyes, beak, brain, liver and spleen. “We had some clues that the liver and spleen have magnetic properties, because they break down red blood cells and so store much iron in the body,” says first author Dr. Clivia Lisowski, from the University of Bonn and the University Hospital Bonn. The liver stood out in the results. Of all tissues tested, it showed the highest concentration of iron. “Iron is crystallised in oxide nanoparticles making the cells superparamagnetic and reactive to magnetic fields. We found by far the strongest magnetic response in liver tissue,” adds Prof. Ulf Wiedwald, from the University of Duisburg-Essen. Further analysis identified liver macrophages as the cells responsible for this effect. To test whether these cells play a role in real-world navigation, researchers trained pigeons to return home from distances of more than 20 kilometres to their aviary in Konstanz, Germany. When macrophages were removed, pigeons were still able to find their way home on sunny days. However, on overcast days, when the sun was obscured, the birds lost their sense of direction. When sunlight was visible, they navigated successfully, suggesting they switch to solar cues when available. Researchers say this indicates pigeons use a combination of magnetic sensing and solar orientation to navigate. Further work using electron microscopy showed that iron-rich macrophages sit close to nerve fibres, suggesting a route by which magnetic information could be transmitted to the brain. Lisowski says: “These findings provide the first concrete evidence of how the Earth’s magnetic field can be perceived within the body and passed on to the brain to guide movement.” On the implications of the research, he adds: “Animal navigation is one of the most fascinating phenomena in nature. If immune cells are part of how birds sense direction, it would fundamentally change how we understand navigation.” Researchers say many questions remain, particularly how the brain interprets signals from these cells. They also suggest the findings could have implications beyond birds, including for species such as sharks that navigate without light, and potentially other animals – and perhaps even humans – that may respond to magnetic fields in ways not yet understood.
Keywords: feature,photo,video,pigeons,birds,animals
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