Horseshoe crabs bleed blue, and that blood clots instantly around bacterial toxins. A test made from it screens nearly every vaccine, IV and implant on Earth, so the industry bleeds hundreds of thousands of them a year.
TED-Ed's primer on the milky-blue blood that became one of the most valuable liquids in medicine.
Not a crab at all but a relative of spiders, essentially unchanged for hundreds of millions of years, with copper-based blood that runs blue.
Business Insider on the bleeding lines and the eye-watering price tag that makes a single gallon worth tens of thousands of dollars.
The LAL test: a clotting reaction from the crab's blood cells that detects bacterial endotoxins down to trace amounts, guarding every injectable drug.
CBS reports on the conservation alarm: crabs bled and released, declining populations, and the migrating red knots that starve without their eggs.
Scientists reconstruct the horseshoe crab's deep evolutionary past to understand a creature we now depend on and endanger at once.
In 2025 the U.S. Pharmacopeia put lab-made recombinant Factor C on equal footing with crab blood, a possible exit from the harvest.