Mantis shrimp are predatory marine crustaceans that live in the shallow waters of tropical and subtropical seas. They make up a small but diverse group of strictly marine crustaceans that are only distantly related to the more common shrimps and crabs.
The stomatopod lineage diverged from other crustaceans 400 million years ago, and today about 350 species are known. Stomatopods are characterized by a pair of large folded limbs that they use to capture their prey--thus the Latin name "mouth foot." These paired limbs are called raptorial appendages, and are analogous to the forelimbs of a praying mantis, which led to the common name of mantis shrimp. Their strike with this raptorial appendage is completed in three to four milliseconds--several times faster than the praying mantis, and comparable in speed to a twenty-four-caliber bullet.
Mantis shrimp have evolved an elaborate visual system that allows them to flourish in the well-lit tropical waters they inhabit. With their complex eyes, these crustaceans have the ability to see polarized and ultraviolet light; many species have three times as many visual pigments as humans.
Mantis shrimp are also capable of monocular stereopsis, or the ability to percieve depth with a single eye. This can be very useful, allowing the animal to perform multiple tasks (observing prey movement with one eye, and judging distance with the other) or function successfully when one eye is lost in combat.