Lost the PENIS Duel... and Became a MOM?!

[00:00:00]This is a coral reef, and this is my pet flatworm [music] who just became a mother. But she wasn't always a she.

[00:00:05]Just 10 days ago, this exact same worm [music] was, well, a boy. Over the next 10 days, he went through the strangest transformation in the entire ocean. My goal was simple, raise a single sea flatworm and keep him alive. Yet his journey was anything but simple. He would have to survive on his own, defend his own body, fall into the weirdest love story in the sea, and end up switching from male to female right in front of me. But we have to go back to day one where you would not believe what I just ordered online. A single tiny package packed with cold seawater shipped straight [music] to my door. And inside, look at this little guy, a living ribbon of black velvet wrapped in glowing pink and orange fire. I would never let anything happen to you. I think I'm going to name you Milo. Now here's the part nobody tells you. A flatworm like Milo isn't really a boy or a girl at all. Every single one of them is a hermaphrodite, born with both male and female parts inside one body. But on day one, Milo was going to live like a boy. He had the equipment to father babies and no intention of ever being the mom. That was the plan anyway. Out in the wild, most baby flatworms never survive their first month. Fish, crabs, hunger, the ocean eats them alive.

[00:01:13]You're going to make it, little man, I promise. At the time, I had no idea how strange that promise was about to get.

[00:01:19]First, Milo needed a home. I wanted to recreate a slice of living reef in a 10-second montage. Live rock, soft coral, [music] a bed of clean sand, and warm saltwater tuned to the exact temperature of a tropical sea. With a few finishing touches, the tank was complete. All that was left was to add him into his new world. Come on, buddy.

[00:01:38]Don't be afraid. This was the first time he had ever touched [music] real coral.

[00:01:42]He glided across the rock like liquid silk, and I knew he was home. On day two, it was time to eat. Who's hungry?

[00:01:48]Flatworms are silent hunters. They don't have teeth or even a real mouth on their face. Instead, Milo pushes his stomach out through the bottom of his body and melts his food from the outside in. His menu, tiny sea squirts and little crustaceans hiding in the rock. He slid over his first meal, wrapped around it, and it simply disappeared. Kind of horrifying, kind of beautiful. By day three, everything looked great. But if we take a closer look, Milo was in danger. All that leftover food had started an ammonia spike, an invisible poison building in the water that could kill him overnight. If [music] I didn't fix it fast, this whole story would end right here. So, this is where these little guys come in. A clean crew of tiny snails and hermit crabs dropped in to scrub the rock and eat every scrap of waste. Go on, get to work. Within hours, they were polishing the glass [music] and the water ran crystal clear again.

[00:02:35]Crisis averted. By day four, Milo had learned every inch of his tank. He hunted at night, hid by day, and grew a little bigger with every meal.

[00:02:44]Everything looked perfect. But a flatworm living completely alone will never do the one thing I actually brought him here to do. And that gave me an idea. So, on day five, I made a confession. I had secretly ordered a second package, a second flatworm, the exact same species as Milo. If Milo was ever going to become a parent, he could not do it alone. The new arrival slid out of the bag and unfurled into the water, just as bright, just as hungry.

[00:03:10]Say hello to Nova. [music] And the moment the two of them sensed each other across the tank, everything changed.

[00:03:16]Because here's the wildest fact about these animals. When two flatworms meet to mate, they do not cuddle. They fight.

[00:03:22]Scientists actually call it penis fencing. Each worm carries two sharp white daggers, and each one is trying to stab the other first, while dodging getting stabbed itself. Whoever lands the hit becomes the father, and whoever gets hit loses. The loser is forced to become the mother, carrying and feeding every single egg all on their own. So, neither of them wants to be the girl.

[00:03:43]Milo reared up, Nova reared up, and they began to fence. For nearly an hour, they circled, lunged, and twisted across the coral, two blades flashing, each one desperate to strike first and stay a boy. I honestly could not look away.

[00:03:57]This was the entire reason I built this tank, and it was more brutal than anything I imagined. Then, in a single flash, it was over. Nova struck. Milo froze. My boy had lost the duel, and in that instant, the transformation began.

[00:04:10]Milo, who had lived his whole life as a he, was now carrying the eggs. Milo was becoming a she right there in front of me. A boy turned into a mother. Over the next few days, the change took over completely. Milo's body swelled with life, glowing brighter than ever. And along the underside of that velvet ribbon, a spiral of tiny eggs appeared, hundreds of them, coiled like a galaxy.

[00:04:31]The boy I ordered 10 days ago was gone.

[00:04:33]In his place drifted a mother, guarding a spiral of new life. By day 10, the eggs were ready. And that is when I realized this story was never really about one little It was about an entire family, about to explode into Milo, my Milo, was going to be the mother of an army. If you want to see me [music] hatch those hundreds of babies and raise them into a glowing reef of their own, be sure to like this video [music] and subscribe for more. I'll see you in the next one.