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How Does the Mussel Grow its Beard?

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Mussels create byssal threads, known as the mussel’s “beard,” to attach themselves to rocks and each other. They use their sensitive foot to mold the threads from scratch and apply a waterproof adhesive that makes superglue jealous.


These California mussels huddle together, hanging on to this rock for dear life.

But if the tumultuous waves should knock one loose, it’s in trouble.

Disconnected and all alone is a very dangerous place to be.

So, it timidly pokes its foot out from between two armored shells …


and makes this.

A byssal thread: a springy lifeline.

It only takes a few minutes to make a single strand.

But now the mussel is literally hanging on by a thread.

It’ll keep going until it’s made 50-100 of these connections – what some call the mussel’s ‘beard.’

It uses it to fasten securely to a rock … preferably next to other mussels.

It’ll even use its foot to drag itself closer to friends.

And why not?

They make great neighbors.

Sticking together makes it harder for hungry predators and crashing waves to pry them loose.

Mussels thrive near the shore where waves churn up food for them to filter out of the water.

If they find a good community … they can stay glued in place for decades.

Long enough for these barnacles to start using them as furniture.

So how exactly does a mussel make a byssal thread?

Turns out it has a miniature thread-making factory in its foot.

It all happens inside this long groove that works like a mold.

Microscopic glands pour in special proteins, which fuse together to form the core of the thread.

Different proteins surround the core, making a tough, protective coating.

To anchor the thread to the rock, the mussel secretes a foamy glue, cementing it in place.

The threads are made of similar stuff as the tendons in our bodies that connect muscles to bone – super strong but also pliable.

The glue it uses to hold on is more than just waterproof.

It hardens in water.

If we could figure out how to make a glue like that, it’d be a game-changer for medicine.

Especially for uses like mending broken bones and closing wounds in delicate surgeries.

Like the ones doctors do on fetuses still in the womb.

Now, with their threads all sorted out, the mussels can finally relax … well, mostly.

I mean, you can’t blame them for being clingy.

They’re just a little … shellfish.

Laura here.

Speaking of attachments – this decorator crab uses tiny hooks on its head to accessorize with bits of kelp, coral, even live sea anemones.

And hey, let’s stay connected, too!

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