Limulus Amebocyte Lysate
Morphologically, the limulus (horseshoe crab) has not changed in 500 million years. Its particularity is that it has no immune system. To make up for this shortfall, its cells produce a protein that converts the haemolymph (equivalent of blood) into a semisolid gel-like substance. This gel quite simply blocks out bacterial infections. Since the 1970s limulus haemolymph has been used to produce a reagent known as Limulus Amebocyte Lysate. It has the property of coagulating instantaneously when it comes into contact with pathogens.