The Mantis Shrimp: Remember the name

Denver Coleman

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       What is your favorite animal in the world? A lion? A tiger? A bear? Oh my! Well, I am here to tell you that your entire life has been a lie. Take your favorite animal, and throw it out the window (figuratively). For there is no organism that can match the pure awesomeness of the Mantis Shrimp (order: Stomatopoda). These crustaceans are basically the Clark Kent of the animal world. They have super-crustacean-speed as well as super vision (and not the kind you needed as a small child). They are able to deliver lighting speed punches without suffering a single scratch to themselves. Scientists have even gone so far as to dub them the fastest appendages in the animal kingdom. Basically if the animal world was the Wild West, when the quick draw was a way to settle disputes, they would be the biggest outlaw this side of the Mississippi. Are you feeling lucky, punk? But wait, that isn't even the half of it. Their vision is nothing short of incredible. While you and I have only three types of photoreceptors in our eyes, these little guys range in the double digits. This allows them to see into a color spectrum that we cannot even begin to imagine. And let's not forget their most important feature; they look totally awesome! Their color patterns look like the mad scribbling of a sugar high four year old. The Mantis Shrimp is the perfect balance of elegance and power. 

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       These predatory crustaceans are typically 20-30 cm in length and are found in tropical and subtropical waters across the world and prey upon other small crustaceans and fish. The Mantis Shrimp is extremely territorial and will ferociously defend their real estate from any animal, regardless of its size, that is ignorant enough to wander through it's territory. While they predominantly live solitary lives they will actively seek out a mate when they need to get down a dirty. The Mantis Shrimp is known as ambush predators because it hunts in a stealth fashion and uses its speed to quickly cover short distances.

        The Stomatopoda order is categorized into groups of spearing and ‘punching’ hunters. These little crustaceans have modified thoracic limbs that have needle-like projections that they use to impale their prey. The Peacock Mantis Shrimp, Odontodactylus scyllarus, is a spearing hunter that stabs its prey with accelerations of up to 65–104 km s^-2 (Patek 2004). That means they are reaching speeds 10x faster than that of gravity. Long story short, it doesn't end well for the unsuspecting fish at the end of those arms. 
      Now the spearing action is fairly impressive but the fascinating physics happens with the ones that use the dactyl heel (hammer-like edge) of their arms to punch their prey to death. They hammer their foe so fast and hard that the water at the impact zone turns into vapor. If only the Mantis Shrimp was able to harness the power of thunder it would probably take over Thor's role in the next Avengers movie. Now you are probably thinking “What’s the big deal? I can punch and stab things too, but do you see a blog about me?” Well hold your horses for a pretty little second, partner. The best part lies in the mechanism behind the Mantis Shrimp’s punching and spearing technique.

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      The Mantis Shrimp’s arms are little bayonets that consist of a series of elastic springs, latches and levers that allows them to amplify the output force of their strikes (Burrows 1969). They are able to force this potential energy with a click mechanism (think safety on a gun) that keeps the limb in place until the Mantis Shrimp wants to deliver a deadly strike. As mentioned earlier, with speeds reaching over 20 m s^-1 the site of impact forms a cavitation- air pocket underwater- which can break through the toughest of shells (Patek et al 2004). Think about how difficult it is to crack open a lobster shell without those crackers that the waiter gives you. During the cavitation event energy is released in the form of light and heat at the impact zone and the imploding bubble creates a secondary shock wave of intense pressure heard as a distinct pop (Burrows 1969). The force delivered is comparable to that of a small caliber bullet. Scorpion from Mortal Kombat may have met his ultimate match.

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       The other fascinating thing about the Mantis Shrimp's smashing technique is that they are able to deliver thousands of deadly blows between molts and not damage their own exoskeleton. Cavitation is seen trailing boat propellers due to the high speed movement through the water. This cavitation event of high heat and impact is the reason why boat captains must continually replace their damaged propellers. However, Currey et al (1982) found the thoracic arms of Mantis Shrimp contain high level of calcium and phosphorous which make it resistant to wearing down. This finding has piqued the interest of scientists to look at their helical stacked fibrous exoskeleton for possible alternative to Kevlar (Taylor 2010). However, issues arise in the lab with studying these guys because the same aspects that make them great predators also contributes to them being horrible pets.  Aquariums usually will not house these animals because they have a tendency to shatter glass and any other living creature inside the enclosure. They can only be kept alone in special impact resistant enclosures.

       So we know the Mantis Shrimp is insanely good at causing death and destruction but these creatures always have a bright outlook on life. By that, I mean they have an insane visual range. Everything that you and I see in the world is through the use of our three photoreceptors: red, blue and green. However, the Mantis Shrimp sees not only visible light like you and me, but also into the ultraviolet and polarized spectrum (Chiao et al 2000). Mantis Shrimp have compound eyes that are separated into groups known as ommatidia. Their eyes are composed of three striated layers of ommatidia that collectively contain ten spectral types of photoreceptors.

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Their visual range goes from 300 nm  to beyond 700 nm (Cronin 1985) which gives them the ability to recognize thousands of color combinations.  However, this super vision comes at a cost. With such a large range of color the Mantis Shrimp sometimes has trouble distinguishing between basic visible light colors such as blue and violet. Since the Mantis Shrimp is unable to distinguish between basic color combinations, they are pretty adept to attack anything that moves. This way they never miss a possible snack. Chiao’s et al (2000) performed an experiment where the Mantis Shrimp had to distinguish between various colored boxes in order to earn a food reward. The results were consistent with the idea that Mantis Shrimp have a hard time distinguishing between the colors of the visible light spectrum.  Its important to note, the scientists who performed this experiment will probably be punched to death for challenging the authority of the Mantis Shrimp with such foolery. Muahahahaha! Regardless of their deficiency to distinguish visible light, they are still incredibly attuned to their colored environment and some ‘push broom’ cameras today were designed based off the eyesight of the  Mantis Shrimp (Brooke 1975).

Here are some partially 'True Facts' about our Mantis Shrimp.

         Between cameras and bulletproof armor, these little crustaceans are able to give scientists new possibilities to improve the world around us. 
          And with that being said, you're welcome for helping you find the greatest creature alive. The Mantis Shrimp is the creature of your dreams as well as your nightmares. They push the envelope of biological design and deserve the title as the greatest extant animal. Only after you accept the Mantis Shrimp into your life, will you be able to fully understand its true awesomeness. However, be warned. If you deny the Mantis Shrimp, they will find you…

References:

Brooke Jr., R.K. 1975. A single-lens multiband camera. Nature 268: 627-628.

Burrows, M. 1969. The mechanics and neural control of the prey capture strike in the Mantid Shrimps Squilla and Hemisquilla. Zeitschrift Fur Vergleichende Physiologie 62:361 -381.

Chiao, C.C., T.W. Cronin, and J. Marshall. 2000. Eye design and color signaling in a Stomatopod crustacean, Gonodactylus smithii. Brain, Behavior and Evolution 56: 107-122.

Cronin, T.W. 1985. The visual pigment of the Stomatopod crustacean, Squilla empusa. Journal of Comparative Physiology 156: 679-687.

Currey, J. D. 1967. The failure of exoskeletons and endoskeletons. Journal of Morphology 123: 1-16.

Patek, S. N., W.L. Korff, and R.L. Caldwell. 2004. Deadly strike mechanism of a Mantis Shrimp. Nature 428: 819 -820.

Patek, S. N., and R. L. Caldwell. 2005. Extreme impact and cavitation forces of a biological hammer: strike forces of the Peacock Mantis Shrimp Odontodactylus scyllarus. The Journal of Experimental Biology 208: 3655-3664.

Taylor, J., and S. Patek. 2010. Ritualized fighting and biological armor: the impact mechanics of the Mantis Shrimp’s telson. Journal of Experimental Biology 213: 3496-3504.