Mantis Shrimp (Stomatopods) By: Alek Kanellopoulos

                                                          Mantis Shrimp (Stomatopods)        

                                                             By: Alek Kanellopoulos
                                                                        Figure 1


Introduction:

Mantis shrimp or stomatopods are marine crustaceans. Their phylogenic placement is as follows:

Kingdom – Animalia
Phylum – Arthropoda
Subphylum – Crustacea
Class – Malacostraca
Subclass – Hoplocarida
Order - Stomatopoda

There are around 400 known species of stomatopods today. Although known as “mantis shrimp” they are neither shrimp nor mantids. They get their name solely from the uncanny resemblance they bear to both organisms. Mantis shrimp are fairly large, with lengths of up to 30 centimeters (About one foot), while some as large as 38 centimeters
have been recorded! Mantis shrimp have a truly massive life span of just over 20 years.

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Mantis shrimp appear in a multitude of colors, often times in beautiful neon arrangements.

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They are quite common in many sub-tropical and tropical marine habitats, but are poorly understood due to an isolated lifestyle in burrows or holes, only coming out to hunt (YES HUNT) or reproduce. They spend most of their time hiding in rock formations, or creating complex tunnels and passageways in the seabed. The majority of stomatopod species can be found in all tropical and sub-tropical seas, although some do live in temperate oceans. Dubbed “thumb splitters” by many, the mantis shrimps’ most amazing trait is its powerful claws known as raptorial appendages. These claws are some of the fastest striking and most powerful (in relation to size of organism) of any of the marine invertebrates. It is through these claws that the species is separated into two distinct groups: Smashers or spearers.


Anatomy:
                                                                           Figure 4

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The most important aspect to note about the mantis shrimp is its amazing raptorial appendage. Shown above, it is composed of a complex musculature that provides for the amazing amount of force that these animals can create. The appendage shown above is that of a spearer, but the anatomy is much of the same for the smasher except the dactyl is replaced with a type of calcified club. Another fact to know is that mantis shrimp have incredible eyes, which are some of the most photoreceptive of any invertebrate, giving it an innate ability to perceive transparencies in prey, and a multitude of different colors. On top of that the eyes move independently from each other, so at all times the mantis shrimp can see a complete peripheral view of its surroundings.

Form and Function:

The mantis shrimps’ diet consists of crustaceans, worms, fish and even cowries. Unlike most arthropods, mantis shrimp do not generally wait for food to come to them; they go out hunting for their meal. Spearers snatch these pray from the water, while smashers simply smash their shells open with their clubs. Both methods of attack can penetrate, stun, and dismember the prey. Mantis shrimp scurry quickly about their environment looking for food in order to be as efficient as possible. What truly makes hunting possible are these amazing raptorial appendages: The spear, and the club.

Spearers:    Solely have a spiny appendage that is used to stab prey and pull it towards the mantis shrimp. The action is unbelievably fast and generally prey cannot even react to the attack.

Smashers:    In contrast, smashers too possess a spear (rudimentary) but also have a highly advanced club that is used to bludgeon and smash prey apart.

Both types of stomatopod strike rapidly by unfolding and swinging the raptorial claw at the prey, and can often inflict incredible damage on much larger organisms. Primarily in smashers, this attack is phenomenally fast; they can instantly propel their club at a rate of 23 meters per second, which is roughly the acceleration of a .22 caliber bullet. Smashers can strike so rapidly that they actually create a fluid dynamic phenomenon known as “cavitation.” Cavitation occurs when there are two drastically different forces moving in water. The reaction creates an explosion, which generates a strong force and can inflict great damage. This often is the case with fast moving boat propellers, when they cause cavitation.
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The cavitation reaction produces measurable forces on mantis shrimp prey in addition to the 1,500 Newton force that is caused by the impact of the club. This shockwave is enough without the club to stun or even kill prey. Pound for pound there is not more dangerous predator anywhere in the ocean!

Mantis shrimps reproduce sexually. Sperm from a male travels up the female’s body cavity and fertilizes the eggs of the female. The female then lays eggs, and is left with the job to carry the eggs under her tail until they hatch. In a lifetime, mantis shrimp can have as many as 20 to 30 breeding cycles due to their long life span. Amazingly, male and female come together not only for mating, but also in monogamous long-term relationships lasting around 20 years!

Mantis shrimp has both and mouth and anus and has a one-way digestive tract. Food is taken in through the mouth and expelled through the anus.

Impact On World:

The mantis shrimp is prevalent in Japanese cuisine, often boiled and eaten as a sushi topping, and occasionally raw as sashimi. They are also quite common in Cantonese cuisine. Mantis Shrimp are known to taste more so like lobster than shrimp, and are heard to be quite delicious.
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Mantis shrimp pose a threat to artificial reef systems, particularly in aquariums, in that they are fervent burrowers. Often times, they will burrow entire canal systems in dead coral, which could have been used for shelter purposes for domestic fish.

Journal Article Review:

Patek, Initials, & Taylor, Initials. (2010). Mantis shrimp bio armor
http://arthropoda.southernfriedscience.com/?p=3558

Patek and Taylor of the Journal of Experimental Biology, studied mantis shrimp and their common sparring habits. They found out that in sparring matches, the mantis shrimp take turns delivering blows to their shield like tail segments, known as telsons. These telsons are incredibly durable, and are able to absorb 70% of the impact from the smasher appendage, much like a punching bag. The strength of the blows is used to establish dominance without resulting in damage between the mantis shrimp and not costing either one their life. They found the durability of the telson is due to heavily mineralized sections of the tail segment.
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List of References:

Mantis shrimp (stomatopods). (2010, December 9). Retrieved from http://en.wikipedia.org/wiki/Mantis_shrimp

Debbie Hauter, Initials. (n.d.). Mantis shrimp - pet or pest. Retrieved from http://saltaquarium.about.com/cs/msubpestmshrimp/a/aa110498.htm

Patek, Initials, & Taylor, Initials. (2010). Mantis shrimp bio armor
http://arthropoda.southernfriedscience.com/?p=3558