Tiny claws of a young shrimp break underwater acceleration record

Large-clawed shrimp juveniles can grasp claws nearly twenty times faster than their parents. Acceleration is like a bullet from a gun, and even faster than that of a mantis shrimp.

Snapping shrimp juveniles have broken the record for accelerating repetitive body movements underwater. Tiny crustaceans can snap their claws at nearly 600,000 meters per second squared, similar to the acceleration of a bullet fired from a gun barrel.

The record clearly beats adult snapping shrimp and even other well-known underwater species such as mantis shrimp, which use their super-fast claws to stab enemies or shove prey.

Big-fingered shrimp (Alpheus heterocheilis), which grow up to several centimeters in length, have spring mechanisms on the larger of the two claws. When this mechanism is triggered, the claw closes, creating a high-speed jet of water and a loud popping sound that startles would-be predators. Previous studies have shown that mature shrimp achieve accelerations of around 30,000 m/s.².

Jacob Harrison and Sheila Patek of Duke University in North Carolina wanted to compare juveniles that are only a few millimeters long. They raised some in a lab and then used a camera attached to a microscope to capture videos of one- and two-month-old babies snapping their claws.

When they tried shooting at 50,000 frames per second — the frame rate they would use for adult shrimp — the claw motion was still blurry, Harrison said. “It was like, ‘Wow, these guys are really cooking.’ It wasn’t until the researchers increased the camera’s speed to 300,000 frames per second that they were able to measure how fast the animals were moving their limbs.

It turned out that young shrimp accelerated their claws up to 580,000 m/s.². This is about 20 times faster than their parents. “These are insanely high accelerations,” says Harrison.

The entire click takes only 300 microseconds – a single moment lasts about 500 times longer. Very few beings can surpass that kind of speed. The only exception is the Dracula ant, which can close its mouth in just 23 microseconds. But it’s easier to move fast in air than in water, which means the shrimp have to work harder to reach the same speed.

Technically, there is one animal that can develop higher acceleration in the underwater world, although in doing so it breaks its spring mechanism. Jellyfish shoot small harpoons at objects that touch their surfaces, and these spikes can develop accelerations almost a hundred times faster than a shrimp’s claw. But each harpoon is unique, because after the shot it remains in the victim.

The comparison makes the shrimp’s accomplishments all the more impressive, Harrison says, adding that the crustaceans’ super-fast limbs could help researchers develop jumping robots and other spring-based devices. “These clicking shrimp have such crazy accelerations,” he says, “but they can do it in the water, and they do it all the time.”