Narrator: For 350 million years they’ve answered to the call of the moon…

They’ve survived ice ages, asteroids, and cataclysmic forces even the dinosaur couldn’t withstand.

While thousands of species came and went. this humble creature endured.

It’s a time traveler, a living fossil... the horseshoe crab.

Their simple design has weathered the eons: Only sharks or sea turtles can penetrate their shells.

Their home is on the ocean floor. They only leave the water to spawn.

After millions of years of evolution, most of the world’s horseshoe crabs are found smack in the middle of the eastern seaboard.

When they’re overturned it seems a miracle they’ve survived at all... but they have an important tool.

Their tail might look like a weapon, but it’s harmless.

They use it to steer and to flip themselves right side up.

They’re more closely related to spiders and scorpions than they are to crabs... and like their relatives, they shed their shells in order to grow – casting off as many as 17 in a lifetime.

10 eyes key them to the light and the cycles of the moon. They even have receptors on their tails.

Their ancient design has changed the course of modern science.

Studies of their vision have led to Nobel Prizes, and their blue blood plays a vital role in human health.

There’s hardly a person alive who doesn’t owe thanks to the horseshoe crab.

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