Useful in many ways, the horseshoe crab has proven uniquely valuable to basic biomedical science.
Crab Blood Could Save Your Life
The blood (hemolymph) of Limulus turns blue when exposed to oxygen, and turns out to be perhaps the most valuable part of this ancient creature, from a human point of view. When a crab receives a wound, cells form a clot, and kill certain kinds of bacteria which are also harmful to humans. This process was discovered in the early 1950s by a scientist named Frederick Bang, who was able to separate the chemical that caused the bacteria-sensitive clots to form. Later, the extract was named LAL (Limulus Amoebocyte Lysate), and it is used to detect whether things that go into the human body--including injectable drugs, needles, and heart valves--are free of dangerous edotoxin producing bacteria. Using LAL is more accurate, simpler, and less expensive than similar tests for bacteria.
Blood is collected from horseshoe crabs taken out of the shallow waters off the Atlantic coast, during the summer months.