For all its tranquility, the sea is a surprisingly noisy place. There are singing whales, pistol shrimps that produce sonic booms, and rowdy shoals of loud-mouthed fish. But of creatures great and small dwelling in our oceans, few come more raucous than a strange species of worm that is no longer than your big toe.
The marine worms, Leocratides kimuraorum, can be found living inside sponges off the coast of Japan at depths of over 100 meters (330 feet). As reported in the journal Current Biology, a team of marine biologist from Kyoto University and the University of Alberta discovered this tiny worm is able to produce a popping noise that reaches around 157 decibels.
For context, human hearing starts to get uncomfortable around 110 decibels, while 130 decibels is our threshold of when it starts to become painful and damaging. A lion can roar as loud as 114 decibels and a howler monkey, the loudest animal in the Americas, can screech at 140 decibels. Even a jet engine taking off for a few meters away is only 150 decibels.
So 157 decibels for a 29-millimeter worm is pretty impressive.
The tiny marine worms take part in an epic dual using their mouths. Sound on!
So, how does this minuscule worm produce such a powerful snap, crackle, and pop? The researchers aren’t entirely sure, especially since it’s fairly unusual for soft-bodied animals to generate loud snapping noises. However, they speculate that it’s generated through a simple muscle contraction that's never been documented before in soft-bodied creatures, which creates a pressure wave similar to snapping shrimps.
"Clearly, even soft-bodied marine invertebrates can produce remarkably loud sounds underwater," the study authors write. "How they do so remains an intriguing biomechanical puzzle that hints at a new type of extreme biology."
“We suggest a novel mechanism for generating ultrafast movements and loud sounds in a soft-bodied animal: thick, muscular pharyngeal walls appear to allow energy storage and cocking; this permits extremely rapid expansion of the pharynx within the worm’s body during the strike, which yields an intense popping sound (likely via cavitation) and a rapid influx of water.”
As for why they make this noise, that’s also a bit of a mystery. Many other small marine beasts use bursts of loud noise to stun their prey. For example, the Synalpheus pinkfloydi shrimp uses its giant right to claw to create a colossal clicking noise. The blast – which produces 210 decibels and an imploding bubble that momentarily generates temperatures of 4,400°C (7,950°F) – is strong enough to knock out its prey. After witnessing their behavior, the researchers think that L kimuraorum uses its sound to stun other worms during a dual, in what they've dubbed “mouth fighting.”
So, next time you're listening to the lapping of waves and staring serenely out at the ocean, spare a thought for the sponge-dwelling worms that are currently in the middle of a shouting match with one another.