Mantis shrimps are known for their rapid and forceful punches, which can reach speeds comparable to a .22 caliber bullet—about 1,316 km/h or 818 mph—making it one of the fastest movements in the animal kingdom. With a single blow, a mantis shrimp can kill prey or defend its territory against rivals.
A study published in Science explores the mechanisms that allow the mantis shrimp's striking limb to unleash such force without risking injury.
Researchers from Northwestern University, led by Nicolas Alderete, used advanced laser techniques, including picosecond laser ultrasonics and transient grating spectroscopy, to understand how the armor in mantis shrimp's claws absorbs high-frequency impacts and to gain detailed insight into its microstructure. These methods allowed them to analyze how stress waves propagate through the mantis shrimp's dactyl club with great precision.
The mantis shrimp's dactyl clubs—claw-like appendages used to deliver strikes—have layered patterns that dampen and filter stress waves. This structure acts as a shield against self-generated shockwaves, allowing the mantis shrimp to deliver powerful blows without suffering damage. The clubs are composed of three specialized layers: the impact surface, the impact region, and the periodic region, each engineered for specific functions.
The outermost layer of the dactyl club is a hard hydroxyapatite coating approximately 70 micrometers thick, which is durable and resists damage, similar to the coating of human teeth. Beneath this coating is an approximately 500-micrometer-thick layer of mineralized chitin fibers arranged in a herringbone pattern, which enhances the club's fracture resistance. Deeper still, the club features a region with twisted fiber bundles organized in a corkscrew-like arrangement known as a Bouligand structure. This structure selectively filters out high-frequency shear waves, contributing to its ability to absorb harmful stress waves.
"Our key finding was the existence of phononic bandgaps in the Bouligand structure," explained Horacio D. Espinosa, a biomechanical engineer and senior author of the study. "These bandgaps filter out harmful stress waves so that they do not propagate back into the shrimp's club and body. They thus preserve the club's integrity and protect soft tissue in the animal's appendage."
The mantis shrimp's strike not only creates a powerful mechanical force but also generates cavitation bubbles by rapidly displacing water and lowering its density. When these bubbles implode, they release intense energy bursts that propagate through the mantis shrimp's club. Despite this, the shrimp does not suffer from the destructive power it creates. "This effectively shields the shrimp from damaging stress waves caused by the direct impact and bubble collapse," Espinosa added.
With a force of up to 1,500 newtons—over a thousand times its body weight—the mantis shrimp can pierce the shells of its victims and even shatter aquarium glass. Scientists have long wondered how a creature that produces such a powerful blow does not harm its own body. The design of the mantis shrimp's armor acts as a phononic shield, filtering high-frequency stress waves to prevent destructive vibrations from propagating into its arm and body.
The article was written with the assistance of a news analysis system.