The Weird and Wonderful World of Sex Under the Sea

"Hermaphroditic marine flatworms (Pseudobiceros hancockanus) are known to duke it out to determine which one will provide the sperm and which one will receive it. These flamboyant, flowy creatures rear up and attempt to stab each other with their dual-pronged penises. The loser will be saddled with the hassle of rearing the young, while the winner gets to go off to fight another sperm-centric battle."