Ever wanted to penis fence but couldn't find a partner?

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Since most flatworm species are hermaphrodites (possessing both male and female sex parts), the decision of who gets to inseminate whom is settled in a rather special way: penis fencing. Two individuals will, quite literally, use their male copulatory parts (called stylets) in bizarrely beautiful combat until one is able to plunge his sperm-delivering organ into the other’s body. The then-labeled “male” in this exchange earnestly injects his sperm, then disengages, leaving the now-female with the burden of bearing the pair’s young.

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But what if a penis-fencing male can’t find a sparring partner? According to new research just published in Proceedings of the Royal Society B, they just inject themselves instead.
They will stab themselves in the head with their needle-like penises and inject sperm to self-fertilize.

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