The lifesaving secret hidden inside a horseshoe crab's blue blood

Horseshoe crabs' blue blood has been used for 40 years to test vaccines and injectable medicines for dangerous bacteria, but the harvesting of approximately 200,000 crabs annually in Massachusetts—tripled over the past 20 years nationwide—has drastically depleted their population and created ripple effects throughout coastal ecosystems. Scientists have developed a lab-made alternative protein that performs equally or better than natural crab blood, and companies like Eli Lilly are transitioning away from using horseshoe crabs, with plans to completely eliminate the practice.