The Longest Relative Penis in Nature
Barnacles have penises up to 8 times their body length — the longest ratio of any animal on Earth.
Barnacles face a unique reproductive challenge: they're permanently cemented to rocks, ships, and even whales. Unable to move, how do they find a mate?
The answer is an extraordinarily long penis. Relative to body size, barnacles have the longest penises in the animal kingdom, reaching up to 8 times their body length. Some species can extend even further.
This remarkable appendage is essentially a searching tool. The barnacle extends it out, sweeping the area around it to find nearby barnacles to mate with. The penis is also remarkably flexible and can change shape depending on water conditions — in calm water, it's long and thin; in rough water, it's shorter and stouter.
Interestingly, barnacles are hermaphrodites (having both male and female organs), but they generally prefer to mate with neighbors rather than self-fertilize. Their extraordinary anatomy makes this possible even when stuck in place forever.