Pseudobiceros sp.

Check this bit from Wikipedia: “Pseudobiceros is a genus of flatworms. Like all flatworms, Pseudobiceros are hermaphrodites. This particular genus engages in penis fencing. When the “winner” touches its penis to the ‘skin’ of the other, insemination occurs, and the “loser” has to bear the burden of motherhood.”

Size: 8cm

Depth: 15m