for National Geographic News
The mantis shrimp is known to see colors invisible to humans and other animals, viewing the world in 11 or 12 primary colors, as opposed to our humble 3.
Now a new study has found that the shrimp also have optimal ability to see different forms of light polarization—directions in which light vibrates.
Humans have been able to see polarized light only within the past decade, and only with the aid of technology, such as digital cameras and polarizers.
"The mantis shrimp is a delightfully weird beastie," said study co-author Andrew White of the University of Queensland in Australia.
"And now we find that this species can see a world invisible to the rest of us."
(Related: "Mice Get 'Human' Vision in Gene Experiment" [March 22, 2007].)
Most animals can tell how fast the electric field in a light wave is oscillating, which is perceived as color.
Blue light oscillates, or vibrates, faster than green, for example, and both of those colors are faster than red. The oscillation's direction is known as polarization.
Many animals, from parakeets to ants, can see linear polarization—what happens when light follows different angles after it's reflected off of water or a transparent membrane such as a fly's wing.
Bees and some birds navigate by polarized skylight, and fish and crustaceans use polarization for navigation and seeing prey.
But mantis shrimp are the first animals known to see both linear polarization and a much rarer type called circular polarization.
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