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Researchers at the University of Bonn have made a groundbreaking discovery regarding how homing pigeons navigate using Earth’s magnetic field. A study published in the journal *Science* suggests that the liver, specifically iron-laden macrophages within it, plays a crucial role in magnetoreception, a function previously attributed to other organs such as the eyes and the beak.
Macrophages, which typically break down old red blood cells and accumulate iron, were found in high concentrations in the liver tissue of pigeons. These cells are positioned near nerve fibers, indicating a potential communication pathway between the macrophages and the nervous system. This finding emerged during a chance meeting between immunologist Christian Kurts and animal behaviorist Martin Wikelski, leading to an investigation into the role of these liver cells in navigation.
In a series of experiments, 34 trained pigeons were tested on a 12-mile route through the German Alps. The researchers disabled the liver macrophages in some of the birds and observed their navigation capabilities. While the pigeons with intact macrophages successfully returned home on overcast days, those with disabled macrophages struggled to find their way, suggesting that the liver’s magnetoreception capabilities are particularly important under such conditions. On clear days, the pigeons were able to navigate using sunlight, indicating that they have multiple navigation strategies.
The study presents a significant advancement in understanding animal navigation, which has puzzled scientists for over a century. However, the findings are not universally accepted, with some researchers advocating for the possibility of multiple mechanisms at play in different species. For example, biophysicist Thorsten Ritz argues that songbirds may rely on light-sensitive molecules in their eyes to detect magnetic fields.
Future research will explore whether other species, such as sea turtles and whales, utilize the same iron-macrophage system for navigation. Additionally, scientists aim to identify the specific nerve pathways that transmit signals from the liver to the brain, further elucidating the complex mechanisms behind animal navigation.
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