The horse shoe crabs survived the great extinction that wiped out the dinosaurs. The copper in their blood clots when exposed to bacteria. Most medicines and vaccines are tested by the blue horse shoe crab blood. They are not quite endangered but these little creatures that out survived the dinosaurs are threatened by humans. Their use for science, for some food, their eggs for migrating bird food and, sometimes even just bait, they are crucial to the survival of so many.
