With its dactyl clubs, the mantis shrimp delivers powerful strikes which generate forces comparable to a .22-caliber bullet. Despite the immense shockwaves produced, it remains unharmed. A new study reveals how this is so.
Mantis shrimp shows its dactyl clubs (in greenish yellow).
Mantis shrimp are equipped with hammer-like dactyl clubs capable of storing and releasing immense energy in an instant. The clubs propel forward with explosive force, shattering mollusk shells and even cracking aquarium glass. A new study led by Northwestern University has discovered that it doesn’t just rely on toughness—it also uses advanced shockwave filtering mechanisms to protect itself.
According to co-corresponding author Horacio D. Espinosa, "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.”
What the Research Uncovered
In the study, the team used transient grating spectroscopy to analyze how stress waves propagate through materials as well as picosecond laser ultrasonics to investigate the microstructure of the mantis shrimp's armor.
The research uncovered two distinct regions within the mantis shrimp’s club. The impact region, which is responsible for delivering crushing blows, comprises mineralized fibers arranged in a herringbone pattern. Beneath this is a region with twisted, corkscrew-like fiber bundles arranged in a Bouligand structure where each layer is progressively rotated relative to its neighbors.
While the herringbone pattern reinforces the club, the corkscrew arrangement acts as a phononic shield, selectively filtering and preventing the high-frequency stress waves from injuring the shrimp.
Future Applications
Understanding the mantis shrimp’s natural defense mechanisms can have far-reaching implications. The findings may inspire new, synthetic sound-filtering materials for protective gear, potentially reducing instances of impact-related injuries in the military and sports.
