Despite its name it isn’t really a crab, and is actually more closely related to spiders, scorpions, and the now extinct Trilobites. They are most commonly found in estuarine environments, which is where rivers meet the sea.

Horseshoe crabs don’t have teeth and use their legs to break up food and move it to their mouths. Its blood is blue because it is copper based and not iron based like yours. It contains a substance called “Limulus Amebocyte Lysate”, or “LAL”. This substance clots or clumps together when it comes in contact with certain bacteria that are difficult to detect otherwise. If you’ve ever had a vaccine or surgery, you can probably thank a horseshoe crab for keeping you safe!