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For thousands of years, a sea creature has plagued sailors by attacking and devouring their ships. It is so destructive that reportedly it swiss-cheesed the hulls of.

Christopher Columbus’s ships, sinking at least two of them. This creature, nicknamed termite of the sea is known as a shipworm and it has an insatiable appetite for wood… even though the ocean has no woody plants. So may I present to you the real Kraken of the sea… a clam.

Shipworms are a group of mostly saltwater clams that look more like a worm than a bivalve. They have a pair of teeny shells on their heads plus rows of file-like teeth that they use to bore their way into the wood, using it as food and shelter. Clams that evolved to eat wood might seem a little odd because … the ocean doesn’t have any trees in it, right?

But there’s actually a lot of wood that makes its way into the ocean especially during strong storms. Damaged coastal trees break off and rivers wash fallen trees downstream into the sea. These clams fill an important ocean niche, degrading all this woody material and recycling the carbon that’s trapped in it.

And these clams are not picky. Any available wood will do. Which means they’ve done a lot of damage to wooden structures that humans use all the time - like docks and ships.

Now, wood isn’t an easy material to digest for any creature. So shipworms get a little help from bacteria to break down things like cellulose and lignin, the hard-to-digest molecules present in plants. Shipworms’ bacteria live in specialized cells on their gills.

These bacteria produce enzymes that travel to the clam’s gut, where they are used by the clam to digest the wood. Among shipworms, the giant shipworm stands out. Not just because of its size.

It’s really big, around 60 cm. But also because it has evolved such a tight partnership with bacteria. This clam came from a wood-eating ancestor, yet its bacteria are a different species than those residing in other shipworms.

While other shipworms use the bacteria to help them eat wood, the giant shipworm no longer needs to eat wood! Instead, it relies on these bacteria to turn hydrogen sulfide, a chemical found in the rotting wood, into food, through a process known as chemosynthesis. Understanding how this partnership evolved could help researchers better understand how other creatures, like mussels, clams, and tube worms, came to live at deep-sea places like hydrothermal vents.

The theory is that things like waterlogged dead trees that have sunk to the seafloor may have been used as an evolutionary stepping stone for organisms to travel from shallow to deeper waters. For all the damage that shipworms have caused throughout the years, from destroying ships to whole harbors, many who study these clams are working on giving them a more positive reputation in society. Because from evolution to history, these little sea creatures have a lot to teach us!

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