25 Interesting Facts About Human Blood

Not All Blood Is Red

While humans have red colored blood, other organisms have blood of varying colors. Crustaceans, spiders, squid, octopuses, and some arthropods have blue blood. Some types of worms and leeches have green blood. Some species of marine worms have violet blood. Insects, including beetles and butterflies, have colorless or pale-yellowish blood. The color of blood is determined by the type of respiratory pigment used to transport oxygen via the circulatory system to cells. The respiratory pigment in humans is a protein called hemoglobin found in red blood cells.