How mantis shrimp survive their own lethal punches

Mantis shrimp are among the ocean’s most formidable predators, delivering one of the most powerful and fastest punches in the animal kingdom. 

With their specialized dactyl clubs, these shrimp can strike with the force of a .22 caliber bullet, shattering mollusk shells and even cracking aquarium glass. But while their blows are lethal to prey, an even greater mystery is how they themselves remain unharmed.

A new study from Northwestern University, published in the journal Science, has revealed the secret behind the mantis shrimp’s resilience. Researchers found that the shrimp’s club structure selectively filters out harmful shockwaves, protecting its delicate tissues from the immense forces it generates. 

This discovery could inspire advanced impact-resistant materialsù for applications in protective gear, military armor, and industrial equipment.

“The mantis shrimp is known for its incredibly powerful strike, which can break mollusk shells and even crack aquarium glass,” said Horacio D. Espinosa, the study’s co-corresponding author. “However, to repeatedly execute these high-impact strikes, the mantis shrimp’s dactyl club must have a robust protection mechanism to prevent self-damage.” 

“Most prior work has focused on the club’s toughness and crack resistance, treating the structure as a toughened impact shield.”

“We found it uses phononic mechanisms – structures that selectively filter stress waves. This enables the shrimp to preserve its striking ability over multiple impacts and prevent soft tissue damage.”

Espinosa, a professor of mechanical engineering at Northwestern’s McCormick School of Engineering, collaborated with M. Abi Ghanem from the Institute of Light and Matter in France to lead this groundbreaking research.

The mantis shrimp’s deadly strike

Mantis shrimp, which inhabit shallow tropical waters, rely on an internal spring-loaded system to deliver their extraordinary punch. Their dactyl clubs store large amounts of energy in elastic structures, held in place by latch-like tendons. 

When the latch is released, the club accelerates faster than a bullet, unleashing a strike that pulverizes shells and deters predators.

This powerful impact has an additional effect: as the club moves through water, it creates a low-pressure zone behind it, forming a small cavitation bubble. When this bubble collapses, it generates a secondary shockwave, adding to the destructive force of the initial strike.

“When the mantis shrimp strikes, the impact generates pressure waves onto its target. It also creates bubbles, which rapidly collapse to produce shockwaves in the megahertz range,” explained Espinosa.

“The collapse of these bubbles releases intense bursts of energy, which travel through the shrimp’s club. This secondary shockwave effect, along with the initial impact force, makes the mantis shrimp’s strike even more devastating.”

Yet despite these immense forces, the mantis shrimp’s own nerves and tissues remain unscathed – a phenomenon that led researchers to investigate the shrimp’s unique biological armor.

A natural shockwave filter

To uncover how mantis shrimp survive their own punches, the researchers examined the microstructure of the dactyl club using two advanced techniques.

The team used transient grating spectroscopy, which tracks how stress waves move through materials, and picosecond laser ultrasonics, which provides high-resolution imaging of structural details.

The analysis revealed that the club consists of two distinct regions, each serving a specialized protective function. The outer impact layer is made of mineralized fibers arranged in a herringbone pattern, reinforcing the club against fractures and absorbing direct impact forces. 

Beneath this layer, a deeper periodic region contains twisted, corkscrew-like fiber bundles arranged in a Bouligand structure, where each layer is slightly rotated relative to the one above it.

Remarkable mantis shrimp armor

The researchers found that this inner periodic region selectively filters out high-frequency shockwaves, preventing harmful vibrations from propagating back into the shrimp’s body. 

This structure, acting as a phononic shield, ensures that only safe, low-energy waves pass through, shielding the shrimp’s delicate tissues from damage.

“The periodic region plays a crucial role in selectively filtering out high-frequency shear waves, which are particularly damaging to biological tissues,” noted Espinosa. “This effectively shields the shrimp from damaging stress waves caused by the direct impact and bubble collapse.”

This discovery provides a new way of thinking about biological impact resistance, suggesting that mantis shrimp armor isn’t just tough – it actively manages and disperses shockwaves to protect the animal from self-inflicted damage.

Materials that mimic the mantis shrimp 

The mantis shrimp’s ability to absorb and filter shockwaves could inspire new synthetic materials with similar properties. 

Protective gear, including helmets, body armor, and industrial shields, could be designed to redirect or absorb impact forces, reducing injuries in fields ranging from sports and military defense to hazardous industrial work.

Beyond impact-resistant materials, this research also has implications for reducing blast-related injuries in military and high-impact environments. 

By developing materials that mimic the shrimp’s phononic properties, researchers could design lightweight protective systems capable of selectively filtering out harmful shockwaves, while allowing less damaging forces to pass through.

Further research is needed

Although this study provides groundbreaking insights into how the mantis shrimp’s club mitigates shockwaves, further research is needed to fully understand the complexities of its design. 

Espinosa and his colleagues plan to conduct 3D simulations to model how the club’s layered structure disperses energy in real-world conditions. 

Additionally, they hope to develop aquatic experiments using state-of-the-art instrumentation to observe how these phononic properties function in submerged environments.

Powerful biological weapons 

Mantis shrimp have evolved one of the most powerful biological weapons in nature, yet they remain unscathed by their own force. 

Their layered dactyl club structure, with its ability to filter and absorb shockwaves, provides a natural model for engineering materials that can withstand repeated high-impact blows.

As scientists continue to explore nature’s designs for solving engineering challenges, the mantis shrimp’s unique armor may hold the key to the next generation of protective technology – one that not only resists impact but manages vibrations in ways that could revolutionize human safety and material science.

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