The Limulus amebocyte lysate (LAL) test is a test used to determine if a bacterial cell produces an endotoxin. ILimulus amebocyte lysate is an aqueous extract of blood cells (amoebocytes) from the horseshoe crab, Limulus polyphemus. LAL reacts with bacterial endotoxin or lipopolysaccharide (LPS), which is a membrane component of Gram negative bacteria.

Testing with the Limulus amoebocyte lysate (LAL) assay. The degree of the reaction is measured with a spectrophotometer.

Horseshoe crab blood provides modern medicine with a substance, Limulus Amebocyte Lysate (LAL), that is crucial for drug testing. LAL clots in the presence of bacterial endotoxins. Because of this, LAL can be used to test for certain bacterial diseases.

Limulus polyphemus was created in 1758.

The scientific name for Limulus polyphemus is Limulus polyphemus. It is also commonly known as the Atlantic horseshoe crab.