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  • All alone, in a vast emptiness.

  • A baby sea urchin. A pleuteus

  • Blind and deaf, its sole purpose is to find the right place to land.

  • Here's what it will become, an adult sea urchin.

  • Basically a rugged ball of spines, built to survive in some of the harshest environments

  • in the ocean.

  • Like their cousins the sea stars and sand dollars, sea urchins have little tube feet.

  • They use them to move around... and pull kelp into their mouths.

  • And between their spines are pincers called pedicellariae that they use to groom themselves.

  • Each spring males release clouds of sperm and females release huge numbers of eggs.

  • A tiny percentage of them find each other in the open ocean.

  • The fertilized egg grows and eventually hatches.

  • An embryo swims for its life.

  • As it grows, it takes on the shape of a little lunar lander.

  • It can swim for weeks or months like this, covering huge distances, feeding on algae

  • along the way.

  • Meanwhile, a microscopic adult urchin is growing inside its own teenage self.

  • The pluteus needs to land somewhere before the adult inside it grows too big.

  • The ocean currents drag it towards shore and into the pounding surf.

  • That turbulence plus the smell of tasty kelp lets the pluteus know, it's time.

  • It stops swimming.

  • It falls to the seafloor.

  • Then something really weird happens.

  • From inside, tube feet reach out

  • It pulls itself inside out, like a sock.

  • Here's a sand dollar doing the same thing.

  • A miniature adult emerges

  • And then, after so much change and tumult, time kind ofstands still.

  • Unless an urchin is eaten or gets sick, it can grow for centuries.

  • Having survived the long odds of youth... it's now practically immortal.

  • Hey, this is Amy!

  • Check out more of our ocean stories.

  • Like this one, about how pygmy seahorses make themselves nearly invisible.

  • Or this one, about how sea otters' fur keeps them warm in frigid water.

  • Thanks for watching!

All alone, in a vast emptiness.

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B2 US urchin sea adult ocean grows kelp

Sea Urchins Pull Themselves Inside Out to be Reborn | Deep Look

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    Amy.Lin posted on 2019/10/28
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