Sensor to detect Earth’s magnetic field discovered in an animal for very first time
It hasbeen a long-held belief in scientific circles that many creatures navigateacross land, through water, and through the skies using the Earth’s magnetic field forguidance. Now scientists and engineers working at The University of Texas atAustin (UT) have finally discovered the organic mechanism responsible for this in ananimal. Looking just like a microscopic TV antenna, the structure has beenfound in the brain of a tiny roundworm that uses it to work out which way toburrow through the soil. This breakthrough may help scientistsdiscover how other species with internal compasses use the magnetic field ofour planet to pilot their course.
Discoveredin an round worm named Caenorhabditis elegans (C. elegans for short), the nanoscale sensor is located atthe end of a neuron protruding from the worm’s brain. This gives rise to thehope that other animals may well share this attribute, particularly as parallelsin brain structures exist across multiple species.
"Chancesare that the same molecules will be used by cuter animals like butterflies andbirds," said Jon Pierce-Shimomura, assistant professor of neuroscience at UT and a member of the research team. "Thisgives us a first foothold in understanding magnetosensation in otheranimals."
The endof the neuron containing the magnetic field sensor in C. elegans is a branched projectioncalled a dendrite. This particular dendrite is anAFD, so named because it has finger-like endings (hence the name, meaningAmphid Fingerlike Dendrite), and is already aparticularly well-known structure in the world of worms as a sensor of carbondioxide levels, ambient temperature, and – as discovered in recent work conducted by UT – humidity.
Buildingon this previous work with C. elegans on the ability of its AFD-paired neuron to react to changes in humidity, the researchers happened acrossthe magnetosensory abilities of the worms when they tried altering the magneticfield around the worms to see what else this sensor could detect. What theydiscovered was that when exposed to alterations in the magnetic field, the wormswere no longer be able to orient themselves up or down intheir environment.
Usinghungry C.elegans implanted in gelatin-filled tubes surrounded by anelectromagnetic coil, theresearchers noted that the worms ordinarily tended to move downward in their environment;an approach they would use when probing for food. When the coil was switched onand a stronger magnetic field than that of the Earth’s was introduced, the wormslost their way and began digging randomly, dependent upon the orientation ofthe induced magnetic field.
Intriguedby this behavior, the researchers hit on the idea of confirming their magneticfield theory by bringing in the same type of worm from various parts of the worldand observing their orientation in a different environment. As a result thevarious C.elegans (fromplaces as diverse as England, Hawaii, and Australia) all moved at exactly theangle in the tubes in relation to the local magnetic field that they would haveperceived as "down" in their home environments. Australian worms, for example,burrowed their way up in the tubes.
The leadauthor of the study, Andrés Vidal-Gadea, former UT researcher and now a faculty member at Illinois State University, noted that C. elegans is just one of manythousands of species that exist in soil, a great number of which are recognizedto move vertically in their environment.
"I'mfascinated by the prospect that magnetic detection could be widespread acrosssoil dwelling organisms," said Vidal-Gadea.
If thismagentosensory ability is widespread amongst soil-dwelling creatures, the teambelieves that one possible use for this discovery would be in the area of pestcontrol in crops where, by simply altering the magnetic field in the land underneaththe vegetation with electromagnetic coils, the creatures would be disoriented, dig down,get lost, and starve.
From a broader perspective, the discovery – if it is made in higher-order species – of a sensor capable of detecting the Earth's magnetic field would provide a vast range of scientific and technological research and application possibilities, with everything from ascertaining the mechanisms behind magnetically-guided migration of animals, through to the improvement of detection devices to aid in our own electronic navigation of the globe.
The results of this research were recently published in the journal eLife.