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Watch a tiny worm make one of the loudest sounds in the ocean

In an ocean filled with whales, sharks, and giant schools of fish, one of the loudest sounds comes from a 29-millimeter-long marine worm, new research reveals.

The worms (Leocratides kimuraorum) were first discovered in 2017. They spend their lives in the crevices of hexactinellid sponges, often called glass sponges, off the coast of Japan. But it wasn’t until researchers brought them to the lab that they noticed how noisy they were.

When the creatures fight, they wriggle toward each other, contract their bodies, and launch themselves headfirst at their opponent, the team found. They also make a loud popping noise that sounds like a champagne cork, underwater microphones revealed. Researchers say the popping sounds emitted by the worms are almost as loud as those of snapping shrimp, which produce sounds so powerful they can break small glass jars.

The worms are otherwise silent, even when the researchers tried to aggravate them. Normally, creatures making a noise like this use a hard structure at some point on their anatomy, like the snapping shrimp, which produces a loud noise by closing its claws rapidly. L. kimuraorum is different in that it is able to generate enough pressure in its body to emit the sound through a simple muscle contraction, the team reports this week in Current Biology.

This is the first recorded instance of a soft-bodied organism or mollusk making a loud underwater noise, the team says. The researchers say that although the popping sound could just be due to rapid movements in the attack, it could also be a call to other worms of the same species to let them know they are under attack. Regardless, their roar makes these soft-bodied creatures seem awfully tough.

*Correction, 20 August, 3:05 p.m.: An earlier version of this story misidentified Leocratides kimuraorum as a mollusk.