It’s easy to assume that big things are more powerful than small things, but time and again within the animal kingdom we find examples of diddy critters doing surprisingly powerful things. One such miniature hero is described in a new study in Current Biology: the shrimp-like organism known as an amphipod. These minute scavengers range from 1 to 340 millimeters and while one claw is modestly sized, the other (much like the famous snapping shrimp) is comparatively huge at almost a third of the amphipods’ body mass. Researchers have discovered they can snap their claw in less than 0.01 of a second, making them the fastest snappers in the ocean.
The researchers from the Patek Lab at Duke University – which specializes in all things small and highly energetic – first became aware of the amphipod's super-click after someone sent them a video. Intrigued as to the mechanics of the sharp snapper, senior author Sheila Patek and colleagues took on the challenge of finding out what was happening. Not an easy task when you’re working with organisms that must be studied under a microscope.
Looking at male Dulichiella appendiculata, which have this enlarged Hellboy-esque "right hand of doom" claw, they discovered the total click was a movement about the width of a human hair and it happened in less than 0.01 of a second. The snaps constitute the smallest and fastest of any documented repeatable movement, made even more impressive by the fact that it’s performed underwater where your very surroundings present an opposing force.
The snaps are actually so quick that they generate water jets, some of which were fast enough to create a cavitation bubble which is when a sudden change in the pressure of a liquid forms a bubble that makes an audible pop sound. It may sound cute, but the researchers posit it’s probably used as a means of defense. It’s a frightening world out there when you’re smaller than a pinhead.
"What's really amazing about these amphipods is that they're sitting right on the boundary of what we think is possible in terms of how small something can be and how fast it can move without self-destructing," said Patek in a statement. "If they accelerated any faster, their bodies would break."
The pistol shrimp also sports one claw significantly larger than the other and is quite the snapper itself. Capable of snapping shut at speeds of around 100 kilometers per hour (62 miles per hour), they create a cavitation bubble that produces sound and light, known as sonoluminescence. The phenomenon is the result of water crashing back down on the negative pressure inside the cavitation bubble creating a momentary burst of heat and light louder than a gunshot that stuns its prey. The noise of a “shrimp layer” joins herring farts as a real headache for submarine crews.