This Creature Has 10 Eyes, Legs That Chew, And Blood That Saves Lives

"KITTS HUMMOCK, Del. — All along the shoreline, for as far as you can see, slick shells of horseshoe crabs glisten in the fading daylight. Listen closely, and you can hear their subtle clacking and the whisper of water over their carapaces.

It’s horseshoe crab spawning season in Delaware Bay. Every May and June, on nights when the moon is new and the tide is high, they crawl onto the beach to mate and bury their eggs.

The ritual goes back 445 million years. Horseshoe crabs are living fossils that have survived four mass extinctions. They are bizarre creatures with 10 eyes that offer insights into how vision evolved. And their blood has saved countless human lives — including yours. "

Sarah Kaplan reports for the Washington Post July 4, 2017.