From Scientific American:
A fierce crustacean known as the peacock mantis shrimp has eyes so refined they can perceive polarized light, including information that is invisible to nearly every other member of the animal kingdom. Not only can the ocean dweller extract polarization information from light, it can do so when the light is circularly polarized—an ability unknown outside a few species of the order of stomatopods to which the peacock mantis belongs.
Unlike linearly polarized light, in which the electric field oscillates along a plane, circularly polarized light's field twists like a spiral spring as the ray propagates. Such light is not commonly reflected from animal bodies and so was long dismissed as a virtual nonfactor in physiology, but research last year showed that some stomatopods have the ability to discriminate circular polarization. A paper published online October 25 in Nature Photonics unpacks the mechanism behind the mantis shrimp's ability and concludes that its eyes handle circularly polarized light more effectively than man-made optical devices do. (Scientific American is part of the Nature Publishing Group.)