Sea turtles and salmon possess an astonishing ability to migrate vast distances from their birthplace and, years later, return to their home territory to reproduce. This navigational feat, known as natal homing, has baffled scientists for many decades. Just how do these animals remember the location of their birthplace with such precision?

A research team from the University of North Carolina at Chapel Hill thinks they may have the answer to that question. The team, led by UNC Professor Kenneth Lohmann, proposes that marine animals such as sea turtles and salmon imprint the magnetic signature of their birthplace early in their development and recall that information when they are ready to return to their home ground to breed. Since the magnetic field of the Earth varies continuously over the planet's surface, each location has a unique magnetic fingerprint—if an animal can remember the unique magnetic identifier of its birthplace, then it holds a map that could someday lead it back home.

The idea that magnetic fields are of navigational use to marine animals is not all that new to Lohmann and his colleagues. In 2001, Lohmann's team published research that indicated young loggerhead turtles use magnetic fields to follow the currents of the North Atlantic. But loggerhead turtles are not the only sea turtle species to tap into the Earth's magnetic field for navigational information. In 2004, Lohmann and colleagues went on to show that green sea turtles (Chelonia mydas) also have their own version of a global positioning system.

The underlying reason marine animals return to their natal home ground remains open to speculation. Professor Lohmann suggests is may be a matter of risk reduction:

"For animals that require highly specific environmental conditions to reproduce, assessing the suitability of an unfamiliar area can be difficult and risky. In effect, these animals seem to have hit on a strategy that if a natal site was good enough for them, then it will be good enough for their offspring." ~ Kenneth Lohmann, PhD, University of North Carolina at Chapel Hill

One thing is certain, there is much to learn about the role the Earth's magnetic field plays in the ability of marine animals to navigate the vast reaches of our planet's oceans and find their way home.

View photographs from the study →

Find out more:

• Lohmann, KJ, Cain SD, Dodge SA, Lohmann C. 2001. Regional Magnetic Fields as Navigational Markers for Sea Turtles. Science. 294: 5541(364-366).
• Lohmann KJ, Lohmann C, Ehrhart LM, Bagley DA, and Swing T. 2004. Geomagnetic Map Used in Sea Turtle Navigation. Nature. 428: 909.
• University of North Carolina. 2008. No Place Like Home: New Theory for How Salmon, Sea Turtles Find Their Birthplace. December 3, 2008.

Photo © Ken Lohmann / University of North Carolina at Chapel Hill.

Alfred Russel Wallace was a self-taught naturalist who is best known for developing a theory of evolutionary origin at about the same time Charles Darwin was putting the finishing touches on his theory of natural selection. Wallace's theory is now vastly overshadowed by Darwin's convincing dissertation on natural selection. But Wallace's thwarted theory represents only a small part of his many accomplishments.

Wallace explored the Malay Archipelago during the 1850s and 1860s. During that time, he observed a wide variety of wildlife and habitats. He collected and catalogued countless specimens for natural history museums. The observations he made, coupled with his curious nature, led him to ask questions about the natural world. Many of those questions focused on the geographical distribution of species: why were species found in certain locations? Today, such questions take refuge in their own field of scientific study: biogeography.

Wallace's observations of species distribution culminated in his identification of a division in the natural world: a line that bisects the Malay Archipelago between the islands of Borneo and Celebes. This line is now know as the Wallace Line. On the west side of the Wallace Line, organisms are of Asian descent. On the east side of the Wallace Line organisms are of Australian descent. You can read more about Alfred Russel Wallace in David Quammen's article, The Man Who Wasn't Darwin, at the National Geographic website. There is also a terrific gallery of images that accompanies the article.

Scientists suspect that the green sea slug (Elysia chlorotica) is guilty of kleptoplasty—the stealing of genetic material from another organism. For some time, experts have known that the green sea slug acquires chloroplasts from the algae it eats. The sea slug stores those chloroplasts in cells that line its gut. There, they act as miniature powerhouses, converting sunlight into sugar. Yet scientists have been puzzled as to how the chloroplasts continue to function on their own. The DNA inside the stolen chloroplasts encodes only about one tenth of the proteins needed to keep it running. So chloroplasts alone do not give the sea slug the ability to photosynthesize.

Research by green sea slug expert Mary Rumpho of the University of Maine may point to the missing piece of the puzzle. Rumpho's observations suggest that the green sea slug may also be stealing nuclear DNA from the algae (in addition to chloroplasts). The sea slug then may be incorporating the algae's DNA it into its own genetic material so it can synthesize the proteins the stolen chloroplasts need to function.

Amphibian populations around the world are in decline due to multiple factors, but one of the most serious threats they face is Chytridiomycosis, a fatal disease caused by the fungus Batrachochytrium dendrobatidis. To combat Chytridiomycosis, conservationists have resorted in some instances to capturing vulnerable amphibians from the wild and placing them in captivity. Now Trent Garner of the Institute of Zoology in London and his colleagues are devising a strategy to treat amphibians in the wild using the antifungal drug itraconazole.