Name: Sea Urchins Pull Themselves Inside Out to be Reborn | Deep Look
Uploaded: 2019-10-28T15:11:03.000Z
Duration: 3 min 23 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

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

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.

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

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.

Here's a sand dollar doing the same thing.

And then, after so much change and tumult, time kind of … stands 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.

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.

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

weird

eventually

vast

basically