Animal IQ

Scientists Just Found Their First Living Giant Shipworm After 300 Years Of Searching

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Lots of giant creatures were the subject of rumor and legend before being officially discovered: the colossal squid, the giant panda, the sasquatch (we aren't giving up hope!). But in the case of the giant shipworm, scientists knew for a fact that it existed thanks to the discovery of its baseball-bat-sized shells. But now that they've actually uncovered a living specimen, they've stumbled on a bigger mystery: how does it eat?

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The mouth of the giant shipworm.
A scientist removes the top of the shell revealing the worm living inside.

A Centuries-Long Search

Biologists have known about the giant shipworm since pretty much the invention of biology. Carl Linnaeus, who introduced Linnaean taxonomy in the 1730s, included the giant shipworm in his seminal Systema Naturae despite never having laid eyes on it. But its existence was well documented in shell fragments, empty shells, and even the fossil record. It's not exactly a fast runner, but the problem was nobody knew where it lived or how it survived. Other shipworms latch onto—you guessed it—ships, and eat their way through the wood. But their giant cousins were never found feeding in this way. That's probably good news for sailors, considering their size, but the 3-foot-long beasts managed to stay out of sight for nearly 300 years.

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So what tipped marine biologists off to the giant shipworm's home? They saw it on TV. A station in the Philippines aired a short documentary about strange shellfish living in a nearby lagoon, and filmed a row of the creatures jutting out of the mud underwater. It soon proved to be a very different animal than its closest relatives. Unlike other shipworms, which are pink, beige, or white, the giant shipworm is an oily black, and looks like something out of a sci-fi horror movie. But even stranger than its size and color is its eating habits—or lack thereof. See, the giant shipworm's mouth is located on the wrong side of its shell, closed off from the world. So how on earth does it survive?

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The length of the giant shipworm after removal from its shell.
Scientists examine a worm removed from the shell.

How To Eat Without Eating

As it turns out, the giant shipworm shares a dietary strategy with tube worms living in one of the most inhospitable environments on earth—one mile below the surface of the water. These tube worms (which are not at all related to the shipworms) don't eat at all. Instead, they position themselves near deep sea vents and survive off of the vents' hydrothermal energy. The giant shipworm does something similar with the gases that build up in the mud where it lives, thanks to a symbiotic relationship with microbial colonies in its gills that transform the gas into an energy source. Actually, a lot of shipworms have similar microbial buddies, but only the giant shipworm relies on them to the extent that its digestive tract is almost entirely vestigial. We're sure it sounds delicious to them, but we're glad we don't have to live off of decaying swamp gases.

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