Everyone knows horsehoe crabs are a evolutionary throwback to prehistoric times. What many don’t realize, however, is the value these creatures hold for the modern scientific and medical industry.
In 1956, scientist Frederick Bang published a paper describing the fascinating capability of the crabs blue-colored blood to detect foreign pathogens and form a gelatinous substance to surround (but not kill) the invading microorganisms. The crab blood can sense even the tiniest concentration of pathogen – one part per trillion – and will form the gel clots right away. The pathogen can then be isolated inside the gel by scientists and identified.
This is what makes it so valuable to the biomedical and pharmaceutical industries. The modern test for contamination using horseshoe crab blood is called LAL (for Limulus amebocyte lysate), and is actually required by the FDA on all new drugs and surgically implanted devices and prostheses.
At several large ‘blood farms’ on the east coast of the United States, adult horseshoe crabs are collected from their coastal habitat and bled. After a percentage of their blood has been collected, they are nursed back to health and released into the wild again. The process is similar to a human donating blood, except it occurs in a tightly controlled sanitary environment, and is obviously not voluntary.
These photos, taken at the Mount Desert Oceanarium in Bar Harbor show the interpretive guide explaining to visitors how horsehoe crabs digestive and reproductive systems work.