Most of us probably owe our lives to horseshoe crabs. Their blue,
copper-based blood contains lysate, which reacts to bacterial toxins by
clotting. Horseshoe crab blood has long been harvested to test
everything from water to intravenous drugs for contamination.
It's also key to making vaccines for diseases such as
COVID-19.
Crabs are returned to the wild afterward but the process may have a
negative effect on spawning. A synthetic version of their blood has been
produced that appears to be on course to eliminate the need to use
animals in endotoxin detection. The pharmaceutical industry is beginning
to accept this substitute but it has not yet ended the practice of
harvesting these crabs for their blood.
