Blue Horseshoe Crab Blood Is Used to Test Medicines

Few people realize how important horseshoe crabs are to modern medicine, says NOAA’s National Ocean Service. The reason is their blood. It is blue and copper-based, and it quickly clots in the presence of bacterial toxins. Because of that reaction, medical researchers use it to test intravenous drugs, vaccines and medical devices, ensuring that they are free of bacterial contamination. Collecting the blood does not require killing the animals. According to NOAA, every year many thousands of horseshoe crabs are harvested from their habitats, bled of about one-third of their blood, and then returned to the beach relatively unharmed. The crabs face other pressures. NOAA lists habitat loss and high demand as commercial bait as continuing concerns, and notes that some states forbid or restrict harvesting. Scientists help to conduct annual spawning surveys around Delaware Bay.