C.M. Martin-Jones et al. / Communications Earth & Environment
One of the magnetofossils detected by the team
Tiny magnetic fossils found in 97 million-year-old sediments may have allowed a mysterious ancient creature to “read” the Earth’s magnetic field as if it were a map. Scientists have no idea what creature it is.
Buried in ancient seabed sediments, millions of years old, they hide tiny magnetic fossils – fragments left by a mysterious organism that has not yet been identified.
In the form of spearheadsspindles, projectiles or needles, and no larger than a bacterial cell, scientists are confident that these magnetofossils have biological origins, but they don’t know what creature produced them, nor why.
An investigation led by the University of Cambridge and the Helmholtz-Zentrum Berlin has now come solve part of this riddlesuggesting that these fossils may have Functioned as an animal GPS systemallowing organisms to “read” the Earth’s magnetic field as if it were a map.
As explained by U.Cambridge in , researchers obtained the first 3D images of the magnetic structure of these fossils, revealing characteristics optimized for detecting both the direction and intensity of the Earth’s magnetic field – thus guiding long-distance migrations.
“Whatever creature produced these magnetofossils, we now know that was most likely capable of accurate navigation», he says Rich Harrisonresearcher in Cambridge’s Department of Earth Sciences, who co-led the research.
With magnetofossils found in sediments with 97 million yearsthe discovery provides the first direct proof that animals have been using the geomagnetic field to orient themselves for at least as long.
The discovery, which was presented in a recently published in the journal Communications Earth & Environmentmay also offer clues about how animals developed this ability, known as “”.
Magnetic perception
Throughout evolution, life has developed a series of extraordinary senses, and magnetoreception is one of the least understood. Some, and insects use the Earth’s magnetic field to navigate over vast distances, but how they detect it remains unclear.
One of the theories proposes that tiny magnetite crystals present in the body align with the Earth’s magnetic field, acting as needles. microscopic compasses.
Certain bacteria, found in lakes and bodies of water around the world, have a primitive form of magnetoreception. Strings of small magnetic particles inside them allow them to align themselves with the magnetic field, helping them swim to the depth they want.
With just 50 to 100 nanometers widethese particles are the perfect compass needles, says Harrison: «if we want to create the most efficient magnetic system, the smaller the better».
But the so-called “giant” magnetofossils studied by Harrison and his team are 10 to 20 times larger than magnetic particles used by bacteria, which has led some scientists to question their ability to navigate.
Harrison, R.J. et al. / Communications Earth & Environment
2D microscopic and magnetic characterization of a giant spearhead-shaped magnetofossil.
In previous work, some researchers have suggested that giant magnetofossils could act as protection.
However, computer simulations indicated that they could also have advanced magnetic properties – something Harrison wanted to explore further. «Everything indicates that this creature carefully controlled the shape and structure of these fossils, and we wanted to understand why», he explains.
Harrison worked closely with Sergio Valenciafrom Helmholtz-Zentrum Berlin, in the definition of the study.
«It was a truly international collaboration, which involved experts from different areas working together to clarify the possible function of these magnetofossils», highlights Valencia.
Harrison and his team applied a new technique to visualize the internal structure of the fossils, revealing how magnetic moments (small magnetic fields generated by the rotation of electrons) are arranged inside the magnetofossil.
Until now, scientists they were unable to obtain images 3D magnetic images of larger particles, such as giant magnetofossils, because X-rays could not penetrate them.
The work became possible thanks to a new technique developed by Claire Donnellyco-author of the study, at the Max Planck Institute, in Germany, and applied at the Diamond X-ray facility, in Oxford.
«The simple fact that we were able to map the internal magnetic structure with magnetic tomography it was already a great resultbut the fact that this data gives us clues about the navigation of creatures millions of years ago is really exciting!”, comments Donnelly.
“It’s fantastic to see our method being used for the first time to study natural samples, which represent a completely different set of challenges to the manufactured samples we normally work with,” he adds. Jeffrey Neethirajana doctoral candidate in Donnelly’s lab.
Specialized in navigation
The images revealed a intricate magnetic configurationwith magnetic moments swirling around a central line that runs through the interior of the fossil, forming a vortex pattern very similar to a tornado.
This vortex magnetism confers ideal properties for navigationexplains Harrison, generating a kind of “oscillation” in response to small variations in the intensity of the magnetic field, which translate into detailed information about the map.
«This magnetic particle not only detects latitude, by sensing the inclination of the Earth’s magnetic field, but also also measures its intensitywhich can vary with longitude», continues Harrison.
The researcher adds that the geometry of this vortex structure is very stablewhich allows it to withstand small environmental disturbances that could otherwise compromise navigation.
«If nature had developed a GPS system – a particle that could be trusted to travel thousands of kilometers across the ocean – would be something like this.”
Narrow the search
By helping to solve the enduring enigma about the function of these fossils, the study also helps to narrow the search to the animal that produced them.
“The next question is: what made these fossils?” asks Harrison. “This tells us that we have to look for a migratory animal that was common enough in the oceans to leave abundant fossil records.”
Harrison speculates that eels could be a potential candidatehaving evolved around 100 million years ago and remaining among the most elusive and least understood animals.
European and American eels travel thousands of kilometers from freshwater rivers to spawn in the Sargasso Sea. Although they can sense the Earth’s magnetic field, how they do so remains a mystery.
magnetite particles have already been detected in eelsbut have not yet been observed directly in its cells and tissues, in part due to their small size and the fact that they can be hidden anywhere in the body.
Although their host remains unknown, “the giant magnetofossils mark a crucial step in understanding how animals transformed basic bacterial magnetoreception into navigation systems highly specialized, similar to a GPS», concludes Harrison.
