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Barnacles Go To Unbelievable Lengths To Hook Up

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Acorn barnacles might look like jagged little rocks at low tide, but they have a surprisingly wild sex life. These crusty little animals — related to crabs and shrimp — have the longest penis of any animal relative to their body size. It’s up to eight times the length of the barnacle itself!


Finding a date is hard enough in San Francisco.

But it’s especially tricky when you’re stuck to a rock in the middle of the bay.

Still, acorn barnacles don’t get discouraged.

These crusty little animals actually have a pretty wild sex life.


At low tide each one is sealed up inside its own miniature fortress – shielded by a ring of armored plates.

The two central plates press together to form a water-tight seal so they don’t dry out in the open air.

They’re ready and waiting for the tide to rise so they can get down to business.

But first they need to freshen up a bit.

The barnacle unfurls eight pairs of delicate feathery legs called cirri, which they use to absorb oxygen from the water.

The legs filter out plankton and debris churned up by the waves, bringing the catch inside to the mouth

They may not look like it from the outside, but beneath their shell, it’s easier to see that barnacles are crustaceans related to crabs and shrimp.

After a nice meal, it’s ready for some action.

The little barnacle lets loose the longest penis of any animal – relative to its body size of course – stretching up to eight times the length of the barnacle itself.

And this penis has skills.

It can taste and smell.

And the tip can feel around, probing to see which neighbors have ripe eggs inside.

When it finds what it’s looking for the barnacle delivers sperm to fertilize the eggs.

Barnacles aren’t exactly prudes.

Pretty much everyone is fair play.

Because they’re all hermaphrodites, simultaneously male and female.

Sometimes it’s one-on-one, sometimes more.

Barnacles are nurturing parents, too.

They hold on to their fertilized eggs and protect them until they hatch.

These cuties are their baby larvae called nauplii.

This is the young barnacles’ chance for adventure.

They roam the sea searching for food and growing.

If they survive long enough the barnacle larvae mature into cyprids.

At this stage the barnacle doesn’t eat.

The cyprid’s only mission is to find the ideal spot to glom onto before it starves.

Having survived the trials of youth, the barnacle settles in.

Now it’s time to get to know the neighbors.

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