Tiny, feisty worms that live off the coast of Japan fight by headbutting each other — and they aren’t quiet about it. During these feuds, the worms emit one of the loudest sounds in the ocean, according to a new study.
The source of the underwater hullabaloo is a nearly transparent segmented worm called the Leocratides kimuraorum, which lives inside sponges 279 to 554 feet (85 to 169 meters) deep off the coast of Japan.

These wigglers are just a tad more than an inch (29 millimeters) long and have lengthy tentacles and a big mouth (literally). These seemingly quiet creatures revealed their true nature under the spotlight in the lab. A group of researchers used an instrument called a hydrophone to record 15 pops that were emitted from three kimuraorums as they were fighting.

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