Sometimes called “living fossils,” horseshoe crabs have patrolled the world’s shallow coastal waters for more than 450 million years, outlasting the dinosaurs. But their population has cratered more than 70 percent since 2000 as a result of over-harvesting and habitat loss. Since the 1970s, horseshoe crabs have been caught, bled alive, and returned to the sea to harvest a protein called “Factor C,” which detects endotoxins that can contaminate drugs. Their bright blue blood is used for testing the safety of biomedical products.

Blue blood. (2026, January 12). Daily Tribune, p. G39.