Why lobsters have blue blood

This chart, made by chemistry teacher Andy Brunning at his blog Compound Interest , explains exactly why this variation occurs:.

Click to enlarge. Compound Interest. Our blood is red because of a protein called hemoglobin. This is the molecule that binds oxygen and allows your red blood cells to carry it throughout your body and supply it to your other cells, and its red because of the iron at its center. As Brunning points out, your blood is red whether it is carrying oxygen or not — diagrams show deoxygenated blood as blue simply for convenience's sake. Horseshoe crabs are bled in the PBS documentary Crash.

These arthropods' blood uses a different protein, called hemocyanin , to bind oxygen. Because that binding process involves an atom of copper, rather than iron, the blood has a blue appearance when it's oxygenated, and little or no color when it's not. Entirely separate from the color, horseshoe crab blood also has a chemical called coagulogen that can detect bacterial contamination at extremely low concentrations.

It's very useful for testing pharmaceuticals, which is why companies collect horseshoe crabs and bleed them alive, as shown in the PBS documentary Crash. A number of other marine species also have hemocyanin in their blood, and depending on the surrounding tissue, it can sometimes appear purplish, like in this red rock crab :. A cut-open red rock crab.

Jerry Kirkhart. Meanwhile, some marine worms such as peanut worms , have purple blood for a different reason: an oxygen-binding protein called hemerythrin.

Like hemocyanin, it only turns color when oxygenated, and in some species — like the peanut worm — you can see this purple color without cutting them open, thanks to somewhat translucent skin:. Finally, there are other marine worms called polychaetes that have blood with yet another oxygen-binding protein, called chlorocruonin. Chemically, it's similar to hemoglobin, and uses iron to bind oxygen.

And though it looks red when concentrated, when it's more diluted, it can appear bright green and, as with peanut worms, can be seen through the skin :. Snails, lobsters and spiders actually have blue blood properly called haemolymph. The colour comes from the copper atoms in the haemocyanin molecule, which is blue when it is carrying an oxygen atom. Haemocyanin, like haemoglobin and chlorophyll in green plants, is a metalloprotein.

This is a protein that contains metal atoms. Nature has plenty of examples of metalloproteins. In fact, plant and animal life forms have evolved with a basic need for metals. A haemocyanin molecule contains two copper atoms that bind a single oxygen molecule O 2 and then release it where it is needed. Haemocyanin is a bluish purple colour when it is carrying an oxygen molecule as seen here beneath the carapace of a Cancer productus crab.

Once haemocyanin releases its oxygen, it is colourless. Haemocyanin in medicine Although haemocyanin comes from a different species to humans about as different as you can get!

One type of haemocyanin is used as a vaccine carrier and also in research into the human immune system and cancer. It is impossible to make this molecule in the laboratory; it is too large and complicated.

The only source is the giant keyhole limpet Megathura crenulata. The molecule is called KLH keyhole limpet haemocyanin. The giant keyhole limpet is only found along the Pacific coastline from California to Mexico.

In contrast, vertebrates and many other animals have red blood from iron-rich hemoglobin. Their blood kind of sloshes around in their bodies carrying oxygen to various organs, as our blood does. Our blood is red because we use hemoglobin to move oxygen around. Horseshoe crabs use a copper-based molecule called hemocyanin to distribute oxygen. Lobsters pee out of their faces.

They have urine-release nozzles right under their eyes. John Mcinnes found this purple, blue and pink speckled lobster in one of his traps last week. The odds of finding a cotton candy lobster are about 1 in million — and yet another one was found off the coast of Maine.

Buster Blue. Buster Blue, a rare blue lobster, was caught in by Captain Pete Begley. Blue lobsters occur about one in every two million lobsters.