The Mantis Shrimp: An Unusual Underwater Inhabitant

There are more than 350 species of mantis shrimp. (Photo credit: SuperStock/Alamy)

The mantis shrimp is neither a mantis nor a shrimp, but it got its name due to its resemblance to both of these creatures. The mantis shrimp is actually a marine crustacean that belongs to the order Stomatopoda. These unusual marine dwellers separated from other crustacean groups about 400 million years ago. Currently, scientists have identified over 350 different species of mantis shrimp. These shrimp are primarily found in tropical and subtropical waters, though some live in temperate ocean habitats.

There are two main types of mantis shrimps. The two types are distinguished by the appearance of their raptorial appendages, or raps. Spearers have sharp barbs on the tip of their rap, which they use to spear soft-bodied prey, such as shrimp or fish. Smashers have a club-like modification on their raptorial appendage, which lets them smash their shelled prey, such as clams and snails. Perhaps what makes the smashers club-like weapon most formidable is the speed at which it can be deployed. Scientists using super-high speed video cameras were able to calculate the speed at which a smasher mantis shrimp strikes its prey. So how fast is a mantis shrimp’s punch? At a speed of nearly 80 kilometers per hour (50 mph), a strike from a mantis shrimp counts as one of the fastest limb movements in the entire animal kingdom.

But their raptorial appendage weaponry is not the only strange thing about mantis shrimp. Mantis shrimp eyesight is also quite unusual. To begin with, their eyes are able to distinguish between 100,000 different colors–that is 10 times the amount that human eyes perceive. Why might mantis shrimp have the ability to perceive such a wide range of wavelengths? It turns out that a number of mantis shrimp species have fluorescent yellow markings on the scales of their antennae and carapace. Research published in January 2004 in the journal Science indicates that the fluorescent markings are part of a threat display directed toward males of the same species as well as potential predators.

A mantis shrimp’s eyes can perceive 10 times as many colors as a human. (Photo credit: Michael Patrick O’Neill/Photo Researchers, Inc.)

The ability to perceive such a wide range of light wavelengths isn’t the only thing that makes a mantis shrimp’s eyes interesting. A mantis shrimp’s eyes are also able to perceive circular polarized light, or CPL, something no other animal can do. Though humans cannot perceive this type of light, we use CPL filters in items such as camera lenses and 3D glasses.

According to research published in March 2008 in the journal Current Biology, one benefit of circular polarization vision is that it enhances contrast in murky conditions, such as the turbid waters that mantis shrimp inhabit, which lets the shrimp see better in their surroundings. In addition, research indicates that the males of some species of mantis shrimp have a patch on their bodies that reflects circular polarized light. Scientists hypothesize that these reflective patches may be used as a part of a sex-specific secret communication channel between mantis shrimp, since other marine animals cannot perceive CPL.

Recent research published in August 2011 in the journal Aquatic Biology indicates that mantis shrimp also communicate by rumbling. Vibrations within the mantis shrimps muscles are responsible for these low-frequency noises. Recordings made near the animals muddy underwater burrows indicate that the mantis shrimp use these noises as a way to establish and maintain territories. Since only males were observed making these noises, scientists think that the rumbling may also be used to attract female mates.

Though these strange underwater creatures have been around for 400 million years, much remains unknown about them, particularly since they spend most of their time in their undersea burrows. Many mantis shrimp species are also nocturnal, which makes tracking their behavior that much more difficult. However, from the data and observations that researchers have been able to gather thus far about mantis shrimp behavior and body composition, it seems these strange marine crustaceans are definitely worth the extra effort required to study them.

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