`Australian scientists are set to announce the discovery of a species of flatworm which is a member of group of predators known as oyster leeches. [..]
The creatures have both male and female parts and engaged in a sexual practice somewhat like penis fencing.
To reproduce they try to stab each other with their genitals and the first to penetrate inserts sperm and then goes on to spar with another flatworm. The “loser” lays and broods the eggs.’