Horseshoe crab blood is a vital resource to the medical field. It's unique in more ways than one: the blue color and its ability to identify bacterial contamination in small quantities. Horseshoe crab blood contains a special amebocyte that is separated and then used in FDA testing. There's a lot of questions as to how blood harvesting affects the American horseshoe crab population, but some researchers are dedicated to the cause of protecting such a significant resource.