
21/08/2025
Male flatworms have a truly unusual way of deciding who takes on the male role during mating. When two meet, they don’t simply pair up — they duel. Using their pen*ses like tiny swords, they “fence” with one another in a contest of strength and persistence.
The winner of this duel claims the role of inseminator, while the loser becomes the one to carry and nurture the fertilized eggs — effectively taking on the role of the mother.
This curious ritual reveals just how inventive nature can be when it comes to reproduction. For flatworms, passing on genes means competing in ways that are both surprising and unique. Their pen*s-fencing battles stand out as one of the most fascinating and unusual reproductive strategies in the animal kingdom.