By: MARGARET MUNRO
The National Post - July 1999
While human beings have to compensate for their limited senses by building sophisticated navigation equipment, the red spotted newt can apparently see the Earth's magnetic field!
But it is still not clear how they detect magnetic fields. There is some evidence that neurons in the noses of trout and salmon act as magnetoreceptors, and that, in other animals, the magnetic field interacts with photoreceptors in the eye or perhaps other organs.
Mark Deutschlander, now at the University of Victoria, and colleagues at Indiana University had a hunch that photoreceptor's (light sensitive regions of a cell) in the brain were key to the red spotted newts' ability to orient themselves in a magnetic field.
To test the newts' navigational skills, scientists fitted dozens of the tiny creature with special caps.
The results, published in the journal, Nature, show that the light receptors are critical to the navigational process.
"If the newt is pointing north, the newts' photoreceptors would align north-south and would show an excitation response, whereas if the newt points itself to the east it would still show an increased pattern but now the pattern will have rotated 90 degrees because the newt has now rotated," he said, cautioning that "we don't know for sure that's what the newts see, but that's how we think of it."
Along with being intriguing, he says it is important to understand how animals sense Earth's magnetic field, given the way human communications and electronic equipment are increasingly bombarding the Earth with electromagnetic signals.
While there is no evidence of a big impact yet - "there is no indication that an increasing number of animals are getting lost" - Deutschlander says a better understanding of how the natural system works may help us save animals in the future.
Scientists have long known that many animals can sense the direction and the strength of Earth's magnetic field. Birds, butterflies and fish are thought to have internal compasses that help guide their incredible migrations, while lizards, newts and many other animals also have a well-honed sense of direction. (The newts involved in the study migrate up to five kilometres back to their natal ponds after spending up to five years living in the forest. They also have no trouble orientating themselves in ponds.)
"It's sensory like vision but with a brightness pattern imposed over what they're looking at due to the direction of the magnetic field," says Deutschlander, the lead author of the paper.
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