The barnacle's penis.

This is a barnacle.

You have probably seen these little rocky warts on the beach attached to rocks and stuff, like the one above. You’d be forgiven (by most people, not by me) for thinking that these are just ugly stoney growths but all 1220 species of barnacle really are Living Things: Crustaceans in fact, related to lobsters and crabs. Barnacles cannot move about on their own and instead opt for a life of attaching onto things – whether that be rocks, boats, seashells, etc – although they do have legs. Legs and they can’t walk?! Those are pretty useless legs I hear ye cry! But nae: the legs of barnacles are modified in such a way that they facilitate feeding. Remaining in their shell, they use their little feathery legs to reach out into the water and beat them rhythmically, in order to swoosh tasty plankton into their shell and eat them all up.

You often find barnacles grouped together in clusters (as in the photo below) because they cannot move and so like to have other barnacles to hang out with*.
*Not scientific fact.

So far we have learned that barnacles can’t move and have useless legs. WHY ARE YOU WRITING ABOUT THEM, LAUREN? Oh I will tell you why, curious reader.

THE BARNACLE HAS THE BIGGEST PENIS (in relation to size) IN THE WORLD.

Most barnacles are actually hermaphrodites, owning both male and female reproductive organs, but although it is possible for them to fertilise their own eggs, this appears to happen rarely: They much prefer to mate with other individuals rather than themselves whenever it is possible to do so. But as we have already discovered, barnacles do not move, so finding a mate can be extremely difficult. It’s not like they can take each other out to an underwater bar and impress each other with their awesome moves on the seafloor.

But let me tell you. If there is one thing a barnacle can move, it is it’s penis. VIDEO EVIDENCE:

Mating barnacles from Casey Dunn on Vimeo.

That is not all. Researchers have discovered that barnacles’ penises can actually change shape to suit their environment. Apparently, barnacles living in gentle waters have long, thin penises which are best for getting reaching far away, whereas those living in rough waters have short, firm penises that are more likely to withstand strong waves. This is a really cool finding (at least it is for those of us obsessed with the genitalia of every species) because it suggests that a creature’s environment can shape its genitals as much as female choice or male competition.

There you have it. The barnacle. And it’s massive shlong. No longer an ugly boat-wart, is it?