How many times can you snap your fingers in a second? Whatever your record, you’re no match for the creature in the video above. This “amphipod”—a microscopic, shrimplike crustacean—snaps its claws thousands of times per second. It’s one of the fastest repeatable movements in the animal kingdom, according to a new study, and one that practically defies the laws of physics.
Amphipods (Dulichiella cf. appendiculata) feed on dead algae and seaweed in the cool coastal waters they call home. Males have a single asymmetric claw that makes up about one-third of their total body mass. This appendage is comprised of a thumblike “propodus” and a hinging “dactyl” that swings open and shut at rapid-fire speed—despite only being as wide as a human hair.
In the new study, scientists placed male amphipods under a high-speed camera that allowed them to precisely position each snap in the frame. The fastest moves happened in less than 50 microseconds, or 10,000 times shorter than the blink of a human eye, the researchers report today in Current Biology. The speed is particularly remarkable, the team says, because the drag of water should slow down the snaps.
The scientists also found that the claws made audible popping sounds and generated water jets with each snap. Some of the jets were so intense, they generated a powerful phenomenon called cavitation, when rapid changes in pressure create bubbles in the water. In the slowed-down video above, you can see an oblong bubble shoot out of the claw each time it slams shut.
The researchers next want to investigate why such a tiny animal needs to make such fast movements. One thought is the amphipods move their claws as communication during territorial or mating disputes. Their message? Snap out of it.
*Correction, 9 February, 3:15 p.m.: This story has been corrected to note that the fastest snaps happened 10,000 times faster than the blink of a human eye.