Lobster blood is blue once it is exposed to air. What color is it inside a living lobster?
The Correct Answer and Explanation is:
Correct Answer:
Inside a living lobster, the blood is colorless or very pale blue.
Explanation:
Lobster blood is not blue while it is still inside the lobster’s body. In fact, it is mostly colorless or a slightly pale blue. The reason for this lies in the type of respiratory pigment lobsters use to transport oxygen.
Humans and many other animals use hemoglobin, a protein that contains iron, to carry oxygen in the blood. Hemoglobin gives our blood a red color when it binds with oxygen. Lobsters, however, do not have hemoglobin. Instead, they rely on a different oxygen-carrying protein called hemocyanin.
Hemocyanin contains copper instead of iron. When oxygen is not bound to hemocyanin — that is, inside the body where oxygen levels are lower — hemocyanin is colorless or very faintly bluish. This is why the blood inside a live lobster is nearly clear.
Once the lobster’s blood is exposed to oxygen in the air, such as when it is injured or cut, the hemocyanin binds with the oxygen. This causes a chemical change that turns the blood a blue color. It is similar to how iron rusts and turns reddish when exposed to oxygen.
This change does not happen instantly. The blood becomes blue only after it is oxygenated, just like the bluish color seen in some veins in the human body due to how light penetrates the skin and reflects off deoxygenated blood.
In summary, the blue color of lobster blood appears only after exposure to air. Inside the lobster, the blood remains clear to pale blue, due to the lack of oxygen binding. The blue color serves as a useful biological clue that hemocyanin is the oxygen carrier in crustaceans like lobsters.
