By Mara Grunbaum
To find a mate, most animals must travel—up a tree, down a stream, across the street to the bar. But not barnacles, which spend their entire adult lives cemented firmly to rocks, boats, whales and the like. To compensate for their immobility, barnacles have evolved the longest penises relative to body size in the animal kingdom.
The appendages can reach up to ten times the length of the barnacles’ bodies to allow them to search of a partner. See a video—safe for work!—below.
According to new research published in Marine Biology, the shape of barnacles’ penises varies depending on their circumstances. Barnacles spaced far apart from each other develop stretchier organs, the better for reaching across the gaps, and barnacles exposed to rough waves grow wider ones to stand up against the tide.