Linear polarization occurs when an electric field of light oscillates back and forth in a straight line. In circular polarization the light oscillates around and around in a circle.
The research, led by Sonja Kleinlogel of the Max Planck Institute of Biophysics in Frankfurt, Germany, appeared recently in the online journal PLoS ONE.
Some scientists have speculated that circular polarization vision is used for sexual signaling.
But study author White said, "We found the same structures in the eyes of both 'boy' and 'girl' mantis shrimps, and yet neither have circularly polarized markings on their bodies."
He believes it makes more sense that mantis shrimp evolved such advanced abilities to detect prey.
"Some of the animals they like to eat are transparent and quite hard to see in seawater," White said.
"I suspect [their prey] light up like Christmas trees as far as these shrimp are concerned."
Raymon Glantz, a professor at Rice University in Texas, called the new study "a first-rate paper." But he's not sure how important the discovery will turn out to be, because circularly polarized light is so rare in nature.
So far, only a handful of sources of circularly polarized light have been found: firefly lanterns, scarab beetle bodies, chlorophyll, and crustacean bodies—including those of mantis shrimp.
"It opens up the possibility that we have in crustaceans complete polarization analyzers," he said.
"What the significance of that is biologically—that's not clear."
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