September 3, 2026

The Astonishing “S3x Battles” of Flatworms: One of Nature’s Most Unusual Reproductive Strategies

This creates a biological conflict that evolution has solved in a surprisingly aggressive manner.

The Duel Begins

When two flatworms encounter one another, they do not immediately exchange reproductive cells.

Instead, they engage in what scientists have famously termed “penis fencing.”

The name may sound humorous, but the process is a genuine and intense reproductive competition.

Each worm attempts to inseminate the other while simultaneously avoiding being inseminated itself.

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