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Penis Fencing
Hermaphroditic flatworms fence with their two-headed penises — the loser gets pregnant and must bear the energy cost of producing eggs.
Flatworm
Platyhelminthes
Many flatworm species are hermaphrodites, possessing both male and female reproductive organs, leading to unusual mating competitions.
Vital Stats
🏷️ TypeFlatworm (invertebrate)
🌍 Found InOceans, freshwater, and moist land habitats worldwide
📏 Size1mm - 50cm depending on species
⏳ LifespanWeeks to years depending on species
💕 Mating SystemHermaphroditic — engage in 'penis fencing' to avoid pregnancy
👶 OffspringLay eggs; some can reproduce by splitting in half
🍆 Penis Size3.0 mm
⏱️ Sex Duration1 hour
🔬 Notable AnatomyTwo sharp, dagger-like penises used to stab opponent during mating
⚖️ Sexual DimorphismN/A — hermaphrodites with both organs