Horseshoe crabs are not much to look at. But beneath their unassuming catcher’s-mitt shell, they harbor a half-billion-year-old secret: a superpower that helped them outlive the dinosaurs and survive all the Earth’s mass extinctions. And what is that secret superpower? Their blood. Their baby blue blood. And it’s so miraculous that for decades, it hasn’t just been saving their butts, it’s been saving ours too.

But that all might be about to change.

Follow us as we follow these ancient critters - from a raunchy beach orgy to a marine blood drive to the most secluded waterslide - and learn a thing or two from them about how much we depend on nature and how much it depends on us.

This episode was reported by Latif Nasser with help from Damiano Marchetti and Lulu Miller, and was produced by Annie McEwen and Matt Kielty with help from Liza Yeager.

Special thanks to Arlene Shaner at the NY Academy of Medicine, Tim Wisniewski at the Alan Mason Cheney Medical Archives at Johns Hopkins University, Jennifer Walton at the library of the Marine Biological Lab, and Glenn Gauvry at the Ecological Research and Development Group.

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