How do barnacles mate?

Helen Scales - You're talking about sperm and eggs, and barnacles if you've ever been down to this shoreline are rooted very solidly to the spot, so how do they move around and find a mate?

Well lots of other marine creatures have a similar problem. Things like corals which are animals, they don't move either but they solve that by sending their sperm and eggs up into the water and hopefully they'll fertilize and they'll meet each other and fertilization will take place and larvae will be created, but that's not what barnacles do. Barnacles look a bit like other types of mollusc on the seashore but they are in fact a type of crustacean, like crabs, and lobsters, and things like that, but very much smaller, but they do actually have sex directly and the only way they can do that is by having a very long appendage.

The male barnacles have very long penises, one of the longest in comparison to the size of the body, that there is in the animal world - animal kingdom, and - Chris Smith - They didn't include me in the analysis - I'd just like to say that.

Helen Scales - No comment - and the barnacle males, will literally poke around next to them and see what they can find, so they don't have much reach really in actual terms but they can reach out and fertilize female barnacles.

Chris Smith - That's amazing! So if you look at the barnacle crop that you see on rocks, do you see sort of concentric rings of males, females -?

Helen Scales - You must see some sort of patterning like that indeed, because you would have to be arranged in space, around on that rock to be able to reach other members of the opposite sex, and they obviously mate with lots of other different barnacles to produce lots of baby barnacles, and but that's how they do it - and that seems rather wonderful. So take a closer look next time you're down on the shore.

Chris Smith - Thank you very much, Helen!