You might know of mantis shrimp for their ridiculously fancy colors or their elaborate eyes, but the feisty crustaceans also pack a considerable punch. Now researchers are beginning to understand how the creatures are able to shatter shells and even glass, while at the same time not hurting themselves.
Some types of mantis shrimp can deliver a devastating punch using their specially adapted appendages, which end in a hammer-like club. Moving these limbs at an impressive 23 meters a second, they can easily crack the shells of their prey. Now a new study published in Advanced Materials has uncovered one of the tricks that the shrimps use to prevent their own clubs from cracking under the immense pressure generated.
It turns out that the shrimp have a particular layer of fibers, known as the striated region, that wrap around the club and compress it. This means that when the crustacean strikes its prey with such shell-smashing force, the shockwaves created are contained, preventing the club from expanding and so stopping it from cracking as a result.
“We believe the role of the fiber-reinforced striated region in the smasher's club is much like the hand wrap used by boxers when they fight: to compress the club and prevent catastrophic cracking,” explained UC Riverside’s David Kisailus. “Together, the impact, periodic and striated regions form a club of incredible strength, durability and impact resistance.”
The research has also shed some light on the evolution of the club-like appendages. Mantis shrimps – known technically as stomatopods – come in one of two different types. There are the “spearers” which, you’ve guessed it, spear soft-bodied prey using barb-tipped limbs, while the “smashers” are thought to have turned this harpoon into the blunt club they now use to crack open shells.
It turns out that the special fibers that the smashers have encasing their club and preventing it from cracking are also found in the weapon of the spearer mantis shrimps. Here, they prevent the harpoon from deforming when it is used to stab prey, but the researchers can now see how the same fibers enabled some shrimp to evolve their spear into the powerful club, which is thought to have happened with the appearance of more hard-shelled prey.
The study has also uncovered how the shape of the smasher enables the shrimp to move it with such awesome speeds in the first place. The profile of the limb is one of a teardrop, reducing resistance as it moves through the water, and generating bubbles that implode, which creates a secondary impact as they hit the prey.
The work will inspire researchers to create better ultra-strong composite materials that could be used in a variety of settings from aerospace to sport to the military.
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