The Medical Contributions of Horseshoe Crabs

By Isabel C.

There exists a keystone species on the coasts of America, Mexico, and Asia that has some of the most valuable blood in the medical world. Since the late 1970s these creatures have been captured and lugged to laboratories where they are safely bled for several hundred milliliters of blood. These are horseshoe crabs, ancient and oddly-shaped creatures possessing blue blood and a unique defense against contaminants. Their diet of clams, crustaceans, and worms exposes them to heavy concentrations of bacteria containing plenty of endotoxins, common contaminants carried in bacteria that can cause a slew of health issues. Horseshoe crabs would be affected if not for the presence of a compound called Limulus Amebocyte Lysate, or LAL, in their amebocytes. It has the ability to form a clot around bacteria in the crab’s bloodstream, completely encapsulating it and protecting against the bacteria’s endotoxins. For the past four decades, this reaction to bacteria has helped manufacture safe vaccines and is continuing to be useful during the rush for COVID-19 vaccinations.

The FDA requires that every drug must be tested for contaminants before getting approved. Drugs used to be tested using live rabbits, but horseshoe crabs beat that method in speed, ease, and ethics. The endotoxin-rich habitat of the horseshoe crab is the reason for its remarkable ability, an ability that can easily be made into a purity test to ward off endotoxins from our own medicine. Endotoxins are particularly dangerous contaminants as they can cause a high fever and toxic shock if injected into someone’s bloodstream. There is no doubt that there has to be a method of detecting and removing even the smallest amount of endotoxins in an injectable drug, and LAL in horseshoe crab blood happens to be the perfect way to do this.