Horseshoe crabs have a wonderful secret buried under their shell: They have blue blood. This blood is special, not only in color, but in function as well. The reason for it’s blue sheen is due to the copper it uses to bind oxygen, rather than iron which we have in hemoglobin in our blood (red coloration). Apart from the blue coloration, the blood has extreme sensitivity to pathogens, or foreign contaminants. When E.coli comes in contact with horseshoe crab blood, it immediately forms clots. The reason for these clots is a compound in the blood called LAL (Limulus Amebocyte Lysate) which is extremely sensitive to foreign fungi, viruses and bacteria.
As a result the Food and Drug Administration (FDA) requires that any new drug be tested using LAL to ensure there is no bacterial contamination. Surgical implants require a similar test as well. The blood, as a result, has become extremely valuable ($15,000 a quart).
The harvesting process involves capturing the horseshoe crabs, removing 30% of their blood and returning them to their natural habitat. This blood volume then recovers within 3 days. The process is not perfect, as 10-15% of the subjects do not survive bleeding.
LAL is another wonderful example of why we should always consult nature when attempting to solve large problems, as nature’s evolutionary forces have been working for a much greater length of time than we humans have been technologically adept.