Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bird’s eye views earth’s magnetic lines

14.05.2004


Nature article reports photoreceptors involved in sensing the earth’s magnetic field



Migratory birds, as well as many other animals, are able to sense the magnetic field of the earth, but how do they do it? "A fascinating possibility is that they may actually see the earth’s magnetic lines as patterns of color or light intensity superimposed on their visual surroundings," said John B. Phillips of Blacksburg, associate professor of biology at Virginia Tech. The results of more than two decades of research allow him to let such an image cross his mind.

A paper in the May 13 issue of Nature, "Resonance effects indicate a radical-pair mechanism for avian magnetic compass," reports evidence that the earth’s magnetic field is sensed by light-absorbing molecules in the retina of a bird’s’ eye.


Thorsten Ritz, a postdoctoral associate in the Phillips’ lab at Virginia Tech who is now a faculty member in the Department of Physics and Astronomy at the University of California, Irvine, co-authored the paper with Peter Thalau of the Zoologisches Institut, Fachbereich Biologie und Informatik, at J.W. Goethe University, Siesmayerstrasse, John Phillips of Virginia Tech, and Roswitha Wiltschko and Wolfgang Wiltschko, also of J.W. Goethe University.

Any effect of the earth’s magnetic field on a photoreceptor’s response to light is expected to be extraordinarily weak -- so weak in fact that the possibility of such effects have been largely ignored. But animals have developed specialized visual systems. "Some animals can see ultraviolet light. Some animals can see polarized light," Phillips said.

How animals’ nervous systems become adapted to detect different things is the subject of Phillips’ research. "As a biologist interested in specialized sensory systems, the question of whether photoreceptors have become specialized for detection of the earths’ magnetic field is a fascinating topic," he said.

Asking the question: "Are magnetic sensing and light sensing related?" Phillip’s lab has conducted research that has demonstrated that the magnetic "compass" sense involves a light-dependent mechanism in some animals. In earlier papers published in Nature, Phillips’ lab showed that changing the color of light altered directional information obtained from the magnetic compass in amphibians, and that the photoreceptors responsible were not located in the eyes, but in the pineal organ, or "third eye," located on top of the head.

For a photoreceptor to detect light, a molecule, referred to as a photopigment, has to absorb light, Phillips said. Light energy then starts a series of biochemical events that result in a change in the electrical charge across the cell membrane. This neural impulse can then be communicated to other cells in the nervous system.

Several theoretical models, including models proposed by lead author Thorsten Ritz and his Ph.D. advisor Klaus Schulten at the University of Illinois at Urbana-Champaign, have suggested ways in which the magnetic field can interact with a photopigment to divert energy and make the photoreceptor more or less responsive to light, Phillips said. These changes in the response to light may depend on the alignment of the earth’s magnetic field relative to the photopigment molecules in the eye, producing a "visual" pattern that could be used to obtain directional ("compass") information from the magnetic field, he said.

Although the earlier studies by Phillips’ lab and others indicated that birds and amphibians’ magnetic compass involves a light-dependent magnetic detector, these findings did not provide convincing evidence that the magnetic field was having a direct effect on the energy states of the photopigment molecules, as suggested in the models by Ritz and Schulten. An alternative suggested by other investigators is that the magnetic field might affect particles of the mineral magnetite, synthesized by living systems, which act like miniature compass needles.

The new experiments reported in the May 13 issue of Nature took advantage of the fact that migratory birds held in "orientation cages" during their normal seasonal migrations use the magnetic field as a source of compass information to hop in the appropriate migratory direction. To distinguish between the photoreceptor and magnetite mechanisms, European robins orienting to the north during the Spring migration were exposed to low-level radio frequencies predicted to disrupt the energy states of any light-absorbing molecules involved in sensing the magnetic field. In the presence of the radio frequency fields, the robins were unable to orient with respect to the magnetic field. This effect was also shown to depend on the alignment of the radio frequency field relative to the earth’s magnetic field, a further prediction of Ritz and Schulten’s model. Alternative mechanisms that involve the alignment of magnetite particles, rather than changes in the energy states of molecules within these particles, would not be affected by the low-level radio frequency fields used in these experiments.

"This is the first data to show that an effect of the magnetic field on energy states of a molecule is the basis of the magnetic compass," Phillips said. "The importance of this finding extends beyond this field of research, because it suggests that interactions much weaker than any thought to be possible in living systems are playing an important role in the behavior of these animals".

Virginia Tech researchers are currently carrying out related experiments to characterize the biophysical basis of the magnetic compass in insects, amphibians, and mice.


About Virginia Tech: Founded in 1872 as a land-grant college, Virginia Tech has grown to become the largest university in the Commonwealth of Virginia. Today, Virginia Tech’s eight colleges are dedicated to putting knowledge to work through teaching, research, and outreach activities and to fulfilling its vision to be among the top 30 research universities in the nation. At its 2,600-acre main campus located in Blacksburg and other campus centers in Northern Virginia, Hampton Roads, Richmond, and Roanoke, Virginia Tech enrolls more than 28,000 full- and part-time undergraduate and graduate students from all 50 states and more than 100 countries in 170 academic degree programs.

Contact Dr. Phillips at jphillip@vt.edu.

Susan Trulove | EurekAlert!
Further information:
http://www.biol.vt.edu/faculty/phillips/
http://today.uci.edu/news/release_detail.asp?key=1151

More articles from Life Sciences:

nachricht The birth of a new protein
20.10.2017 | University of Arizona

nachricht Building New Moss Factories
20.10.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>