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Appendage strikes with a tremendous force: Mantis shrimp


Mantis Shrimp / Andy Law / LicenseCC-by-nc-nd - Attribution Non-commercial No Derivatives

The raptorial appendage of the mantis shrimp strikes with a tremendous amount of force through power amplification.

The mantis shrimp is an aggressive marine crustacean that uses a hammer-like strike to destroy the shells of mollusks and expose the soft body of the animal. It can even smash aquarium glass. It does this with a unique raptorial appendage--a single foreleg specialized for protection and feeding. The raptorial appendage is divided into three segments. The merus (closest to the body) houses the major muscle groups. Next, is the propus (the middle segment), followed by the dactyl which differs in morphology depending on the species. While there are many different species of mantis shrimp, the mechanics of the raptorial appendage operates under the same general principle. This principle is called power amplification. It uses a balance of muscle contraction and energy storage that allows the shrimp to strike. 
First is muscle contraction. To begin, the lateral extensor muscle (LEM) in the merus contracts. This tightens the saddle structure on the top of the merus like compressing a spring. In addition, it pulls the attached propus and dactyl segments close to the body. When the LEM contracts, it engages a second group--the meral-V and flexor muscle--located in the merus segment. The flexor muscle is a small muscle located below the LEM, and contracts concurrently. Connected to the flexor is the meral-V, the terminal portion of the merus. The exterior of the meral-V has a bulbous shape that hooks into a divot in the caprus (the proximal end of the propus). The contraction of the flexor muscles engages the meral-V in a latch mechanism to help keep the LEM contracted and the saddle from relaxing. This is similar to how a spring-loaded mouse trap works.  
Second is energy conservation. Under the law of conservation, the energy used to contract the muscles has to go somewhere. In the mantis shrimp, it is stored within the contracted merus segment via spring energy in the saddle muscle and elastic energy in the LEM. 
Finally, when it is time to strike, the brain tells the LEM and flexor muscles to relax. Within a matter of milliseconds the muscles relax, the meral-V mechanism unlatches (“the mouse trap”), the saddle and merus expand, and the dactyl segment springs forward. During this final step between 70% and 80% of the stored energy is released.

Watch this video to see a mantis shrimp in action, and watch this video to see how engineers are already mimicking the mantis shrimp to develop strong materials. An in-depth description of the mantis shrimp and its abilities can be found in this TED talk by Sheila Patek. And check out this related strategy of how the mantis shrimp creates a cavitation bubble to create even more force.

This summary was contributed by Allie Miller.

"One hypothesized elastic storage structure, the saddle, only contributed approximately 11% of the total measured force, thus suggesting that primary site of elastic energy storage is in the mineralized ventral bars found in the merus segment of the raptorial appendages." (Zack et al., 2009:4002) 

“Skeletal structures can channel work into elastic materials; when these structures are allowed to relax to their resting state, energy is released over a much shorter time scale than the underlying muscle contraction, thereby resulting in power amplification...The use of elastic structures to amplify the power output of skeletal muscle is fundamental to rapid accelerations in animals.”  (Zack et al., 2009:4002)  


“Two key structures have been identified as probable energy storage structures – the meral-V and saddle...A “ventral bar” of exoskeleton that extended from the meral-V to the ventral surface of the merus in the peacock mantis shrimp...and acts as part of a four-bar linkage system to couple stored elastic energy to the rapid rotation of the carpus.” (Zack et al., 2009:4003)

About the inspiring organism
Common name: mantis shrimp

Learn more at
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist

IUCN Red List Status: Unknown

Bioinspired products and application ideas

Application Ideas: Stronger manufacturing or architectural materials. Device for using release of elastic energy. Use in personal protective equipment (body armor, hard hats, etc.) Creating better impact tools to withstand repeated use. Better shock absorption in cars to prevent transmission of damage to passengers.

Industrial Sector(s) interested in this strategy: Manufacturing, Construction, Personal protection, Impact tools, Automotive

The Patek Lab
Sheila N. Patek
Biology Department, University of Massachusetts
Zack, TI; Claverie, T; Patek, SN. 2009. Elastic energy storage in the mantis shrimp's fast predatory strike. Journal of Experimental Biology. 212(24): 4002-4009.
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Knight, Kathryn. 2009. Elastic energy powers mantis shrimp punch. Journal of Experimental Biology. 212(24): iii.
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Patek S.N.; Rosario M.V.; Taylor J.R.A. 2012. Comparative spring mechanics in mantis shrimp. The Journal of Experimental Biology. 216: 1317-1329.
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