Animals' "sixth sense" is more widespread than previously thought

 A study using fruit flies, led by researchers from the Universities of Manchester and Leicester and funded by the National Physical Laboratory, suggests that the ability of animals to sense a magnetic field is more widespread than previously thought.

The paper, which was published today in Nature, advances our understanding of how animals sense and respond to magnetic fields in their environment.

This new knowledge could also lead to the development of novel measurement tools that use magnetic fields to selectively stimulate the activity of biological cells, including those in humans.

The researchers demonstrate for the first time that a molecule found in all living cells called flavin adenine dinucleotide (or FAD for short) can impart magnetic sensitivity to a biological system in sufficient quantities.

Scientists already know that animals like the monarch butterfly, pigeon, turtle, and others use the earth's magnetic field to navigate long distances. However, the discovery could imply that the biological molecules required to sense magnetic fields are present in all living things, to varying degrees.

"How we sense the external world, from vision and hearing to touch, taste, and smell, is well understood," said co-lead researcher and neuroscientist Professor Richard Baines of The University of Manchester. "This study has made significant advances in understanding how animals sense and respond to external magnetic fields—a very active and disputed field," says the study's author.

To accomplish this, the researchers used the fruit fly (Drosophila melanogaster) to manipulate gene expression and test their theories. The fruit fly, despite its appearance, has a nervous system that functions exactly like ours and has been used as a model in numerous studies to better understand human biology.

The sixth sense, magnetoreception, is much more difficult to detect than the five more familiar senses of vision, smell, hearing, touch, and taste.

According to co-lead researcher and neuroscientist Dr. Adam Bradlaugh of the University of Manchester, this is because a magnetic field carries very little energy, as opposed to photons of light or sound waves used by the other senses, which pack a powerful punch.

Nature has used quantum physics and cryptochrome, a light-sensitive protein found in animals and plants, to get around this.

"The absorption of light by the cryptochrome results in movement of an electron within the protein, which, due to quantum physics, can generate an active form of the cryptochrome that occupies one of two states," said Dr. Alex Jones, a quantum chemist from the National Physical Laboratory who was also part of the team. "The presence of a magnetic field influences the relative populations of the two states, which influences the protein's "active life."

According to Dr. Bradlaugh, "One of our most striking discoveries, and one that contradicts current thinking, is that cells can "sense" magnetic fields even when only a very small fragment of cryptochrome is present. This demonstrates that cells can sense magnetic fields in other ways, at least in the laboratory.

"We identify a possible "other way," he added "by demonstrating that a basic molecule found in all cells can, in sufficient quantities, impart magnetic sensitivity without the presence of cryptochromes. The light sensor, flavin adenine dinucleotide (or FAD for short), normally binds to cryptochromes to support magnetosensitivity.

According to the researchers, the findings are significant because understanding the molecular machinery that allows a cell to sense a magnetic field allows us to better understand how environmental factors (such as electromagnetic noise from telecommunications) may impact animals that rely on a magnetic sense to survive.

The magnetic field effects on FAD in the absence of cryptochrome also hint at the evolutionary origins of magnetoreception, as cryptochrome appears to have evolved to exploit magnetic field effects on this ubiquitous and biologically ancient metabolite.

"This study may ultimatelye allow us to better appreciate the effects that magnetic field exposure may potentially have on humans," said co-lead author Professor Ezio Rosato of the University of Leicester. Furthermore, because FAD and other components of these molecular machines are found in many cells, this new understanding may open up new avenues of research into manipulating the activation of target genes using magnetic fields. "That is considered the holy grail as an experimental tool and possibly, eventually, for clinical use."

By : PHYSOORG