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The Pyrenean ibex, an impressive mountain goat that lived in the central Pyrenees in Spain, went extinct in 2000. But a...
Tight budgets are forcing NASA to consider turning off one or more planetary science projects that have completed their...
Ebola is not a stranger to West Africa—an outbreak in the 1990s killed chimpanzees and sickened one researcher. But the...
In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...
Tropical disease experts tried and failed before to eradicate yaws, a rare disfiguring disease of poor countries. Now,...
Since 2002, researchers have reported that agricultural communities in the hot and humid Pacific Coast of Central...
Balkan endemic kidney disease surfaced in the 1950s and for decades defied attempts to finger the cause. It occurred...
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How Salmon See the World Anew
18 March 2004 (All day)
If you were used to finding food by day then suddenly switched to chasing your dinner in the dark, night-vision goggles might be a necessity. The concept applies to salmon too: New research suggests that the fish adjust the light-sensitive pigments in their eyes as they age and move to deeper waters.
When young pink salmon graduate from shallow streams to the open ocean, they also change their eating habits--from nibbling plankton on the surface to hunting fish in deep water. Scientists suspected that the salmon visual system adapted as the fish moved from shallow waters dominated by ultraviolet light to deeper waters filled with blue and green light, but they had only hunches about how this might happen.
The new study suggests that the salmon's secret is shuffling the light-sensitive pigments inside their cone cells--nerve cells in the retina that respond to light. Iñigo Novales Flamarique and Christiana Cheng of Simon Fraser University in Burnaby, British Columbia, came to that conclusion by examining the retinas of young Pacific pink salmon. They couldn't find any cone cells with blue-light sensitive pigments. But in the retinas of older salmon, such cones were common. And in fish of intermediate age, the pair spotted UV-light sensitive pigments at the cell's tip, but blue-light sensitive pigments at the base, suggesting the salmon were pumping those pigments into their UV-light sensitive cones. The scientists report their findings in the 18 March issue of Nature.
“The work is very interesting,” says Juliet Parry of University College London, adding that many researchers had assumed that salmon tweaked their vision by replacing entire cone cells, not merely replacing the pigment. Novales Flamarique suspects this potential for pigment change may be widespread in vertebrates and has been overlooked because it's difficult to detect in the tiny cone cells. Clearly there is more to color vision than meets the eye.