Lobster blood is blue, as are several other anthropods, including spiders, horseshoe crabs, crawfish, and most other mollusks such as clams, muscles, and snails. Anthropods do not have hemoglobin in their blood, as mammals do, causing blood to appear red due to the presence of iron. Instead, anthropods have hemocyanin, which contains copper, causing blood that appears blue. In both cases, the blood needs the presence of oxygen to appear colored. There is some initial hope that blue blood from lobsters can help human health, as a medicine against cancer and viruses. Hemocyanin acts as a potent stimulant for the immune systems of mammals. While actual treatment is not yet available, it may not be too far down the road, and we will be treating people with blue lobster blood.