Is blood only red?

A few weeks back, I had stayed up until 10:00 on a Friday night working on my English Short Story Assignment. Tired from trying to read it, I closed the book, but in the process of doing so, I got a papercut with dark, red blood jutting out from my finger. After washing my finger and applying a band aid to my it, I wondered if all species had the same colour of blood. Wanting to learn more about how blood is produced and if the colour between all species was the same, I decided to research it.


Illustration from Anatomy & Physiology © Mdf, CC BY-SA 3.0

Blood is composed of multiple elements:  platelets and white blood cells (which compose about one percent of your blood), plasma(which composes fifty-five percent of your blood) and red blood cells (which composes forty-five percent of your blood):

  • Platelets are created in the bone marrow and help to control the flow of blood during times of bleeding.
  • White blood cells help to fight infections, help with the blood clotting process and eliminate unnecessary and potentially harmful bacteria.
  • Plasma is comprised of water and salts which are obtained from the digestive tract and serves as a transportation system for all elements of blood.
  • Red blood cells, with production controlled by the kidneys and produced by the body’s bone marrow which are then instated into the bloodstream with the purpose of transporting oxygen to your body. The protein inside your blood cells is called hemoglobin and is responsible for the appearance of our blood and to ensure that the oxygen is transported to all parts of the body.

The interesting thing is that animal blood is as I mentioned before, not the same colour as human blood. In fact, animal blood varies in colour due to the chemistry of the oxygen molecules. As we know from before, human blood uses hemoglobin which is red in colour because of the hemoglobin’s iron content. Lobsters, horseshoe crabs and octopi utilize hemocynin which is blue in colour because of the hemocynin’s copper content.

However, the interesting thing is that green- blooded lizards utilize hemoglobin even though hemoglobin creates a reddish hue. This attributes to the fact that their blood contains biliverdin and that their blood contains so much green pigment that the reddish hue of their blood is discarded. Biliverdin is extremely deadly and it is astonishing to see the lizards survive with it. This can perhaps be of biomedical interest as we can use it to solve diseases such as malaria

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