How This Teeny-Tiny Sea Critter Strikes Like Mike Tyson

At less than a quarter of an inch long, the amphipod – a crustacean that looks a bit like a shrimp – lives a quiet life and sifts through algae up and down the East Coast. Well, this is superficial quiet, as scientists have just discovered. A man’s amphipod carries a massive claw that can exceed a third of its mass, and if it hits it in less than a 10,000th of a second, it must fight a rechargeable water jet to make its displeasure known. Thanks to a $ 150,000 camera shooting at 300,000 frames per second, researchers have captured a male amphipod for the first time, a moment so violent that it is almost enough to explode the animal.

You’re probably wondering how to piss off a male amphipod experimentally – more specifically the species Dulichiella vgl. appended. So I’ll tell you. While working in the laboratory, the researchers glued toothpicks to the backs of the animals and then attached the toothpicks to ‘micromanipulators’, allowing them to position the amphipods precisely. All they had to do was hang single hairs from a paintbrush near the amphipods, violating their personal space. And then, SNAP. “They are clearly using it in an aggressive context,” said Duke University biologist Sheila Patek, co-author of the paper.

With the ultra-fast camera rolling, Patek and her colleagues made the invisible suddenly visible. “In a way, it’s almost magical,” Patek says. Previously, you only hear or feel an amphipod clip if you have one in a tray, and not if you watch one in the wild. “But to get the whole thing in focus and nicely lit up, you can suddenly see this little attachment fill the screen, load and then crack,” she says.

The critical part of the appendix, more formally known as a gnathopod, is called the dactyl. In the image above, it is the long, blade-like structure at the top of the claw. It is not thicker than a human hair. To snap, the amphipod contracts a muscle, pulls the dactyl back, and stores an incredible amount of energy. Patek and her colleagues need to do more work to fully understand the morphology of how the snap works, but it is likely that a latch will hold the dactyl in place. When the animal is ready to snap, it releases the latch, freeing the claw’s storage energy.

And when we looked further, we were like, ‘Wait, there’s a Water jet get out there! ‘”Says Patek. More specifically, the force of the claw water appears to push at an oblique angle, rather than being completely straight forward. ‘And then, oh woe, the water jet seems so now and then cavitation, what is the formation of these vapor bubbles, what happens when you flow at these extraordinary speeds. When these small cavitation bubbles collapse, they fall explode, explosion of an explosion of energy. This kind of force is in fact so powerful that when boat propellers create their own cavitation bubbles, the force eventually chews on the metal of the blade.