Roundworms, fruit flies, butterflies, fish, pigeons, bats use the Earth's magnetic field for navigation. A person is deprived of such abilities and without special devices he goes astray. How the natural biocompass works - in the material of RIA Novosti.
Worms think
The roundworm Caenorhabditis elegans, which occupies the lowest rung in the animal kingdom, has a small outgrowth in the brain, at the end of the AFD neuron, similar to a microscopic television antenna. This is a bio-compass with which the worm navigates through the soil.
Thanks to the biocompass, the worm moves down in search of food. In an experiment by scientists at the University of Texas (USA), worms lost their orientation and moved chaotically if the magnetic field was distorted around them. Further experiments showed that the trajectory also depends on in which part of the world the worms were born and raised. Thus, the "indigenous Texans" moved parallel to the surface of the earth, and the Hawaiian, British and Australian worms - at an angle that corresponded to the distortion of the magnetic field lines characteristic of their native places.
A process-biocompass in the brain of a nematode worm / illustration by RIA Novosti.
Fish sniff
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In fish, a biocompass that reacts to the earth's magnetic field is located in the nose. Scientists from the University of Ludwig Maximilian (Germany) were able to isolate cells from the nose of rainbow trout (Oncorhynchus mykiss), which contained particles of magnetite, a mineral that plays an important role in the ability of some living organisms to determine the direction of movement. According to researchers, in the nasal region of each individual there are from ten to one hundred such cells, which allows the fish to determine not only the direction to the north, but also to orient themselves in latitude and longitude.
Scientists believe that it is thanks to the supersensitive nose that the trout travels from rivers to the sea for three hundred kilometers, and after a few years it returns to the place where it was born.
Thanks to the special cells in the nasal region, rainbow trout always returns to the place where it was born / CC BY 2.0 / Jon Nelson.
Insects rely on proteins
Fruit flies also have their own biocompass - it is a structure of two proteins formed on the surface of cell membranes. Cryptochrome (Cry) allows cells to perceive blue and ultraviolet light. The main function of the second protein (CG8198) is the regulation of biorhythms in the body, but in combination with cryptochrome it forms a kind of nano-needle. Its center shaft is CG8198 and its shell is Cry.
Such a needle, like a compass needle, aligns even with a weak magnetic field. During the study, Chinese scientists had to replace metal instruments with plastic ones, since the protein structures under study were highly magnetized and adhered to the metal.
The open protein complex was named MagR (magnetic receptor). Exactly how it works is still unclear, but scientists have suggested that proteins, sending signals to the nervous system, help Drosophila understand where the north is.
Drosophila senses the Earth's magnetic field thanks to the MagR protein complex / Photo: Muhammad Mahdi Karim.
Birds count and measure
Monarch butterflies and some birds, in particular pigeons, have a magnetic receptor. In birds, a type of cryptochrome, Cry 1a, is found in cells of the retina that are sensitive to blue and ultraviolet rays, and it reacts to a magnetic field only after light activation. But even that doesn't fully explain how the bird's navigation system works. Indeed, when orienting in space, birds use two "bio-navigation maps" at once - smell and magnetic.
Thanks to the magnetic bird, they distinguish the directions to the north and south, calculate the longitude, measure the declination (the difference between the magnetic and the geographical north) of the Earth's magnetic field, this helps them to orient themselves and correct the route.
Scientists believe that birds travel most of the way relying on the magnetic field, and smells play a more important role at the finish line. The pigeons with which the nostrils were plugged cut the olfactory nerve, destroyed the olfactory epithelium by washing the beak with an aqueous solution of zinc sulfate, and spent more time returning to their dovecote than ordinary birds.
Not all scientists agree that Cry 1a protein serves birds for navigation / CC BY-SA 2.5 / Alan D. Wilson / Feral Rock Dove at the Burnaby Lake Regional Park in Burnaby, BC, Canada.
Bats Check with the Sun
In 2016, scientists from the Max Planck Institute for the Study of the Brain (Germany) discovered the navigation protein Cry, or its variant Cry 1a, in the cells of ninety mammalian species. And, say, rodents and bats, which clearly react to magnetic fields, did not have this protein.
Some species of bats - in particular, the great bat (Myotis myotis) - not only correct their flight according to the Earth's magnetic field, but also daily check their biocompass against the sun - more precisely, against the polarized light, which is brightest at sunset.
This was confirmed by the experiments of German and Bulgarian scientists. Bats were placed in a modified magnetic field (shifted 90 degrees east) during sunset. Some of the animals were in containers and could not see the rays of the setting sun. As a result, when they were released, they deviated from the course just by the angle of inclination of the beams in the boxes and went astray. Mice that could compare their feelings with the sun did not experience such difficulties and returned safely to their native cave.
Biocompass for humans
In humans, there is no process in the brain, no cells with magnetite, no navigation proteins in cells. He goes astray without special devices, if there are no high landmarks on the route. This often happens in the forest.
American engineers Liviu Babitz and Scott Cohen propose to correct this misunderstanding with the help of an implant that acts as a biocompass - like in animals. A silicone device the size of a matchbox vibrates every time a person turns north. The inventors have implanted a biocompass under their skin.
Alfiya Enikeeva