Barnacles live firmly anchored to ocean rocks, and they can't move around to mate. To solve this problem, barnacles have evolved the longest penis relative to body size of any animal on earth, up to 8 times longer than body size. New research now reveals the hows and whys of penis size and shape variation among barnacles.
Barnacles seem to be able to change the size and shape of their penises to match local wave conditions.
When wave action is light, a longer (thinner) penis can reach more mates, but at times of higher wave action, a shorter (stouter) penis is more manoeuvrable in flow and therefore can reach more mates.
Where there's a will, there's a way. Tweet